notebook.community

Edit and run

Lógica de primer orden

Para trabajar con lógica de primer orden, vamos a utilizar el paquete nltk, y en particular su módulo de inferencia lógia y de construcción de modelos.





In [1]:



    


from nltk import *



    











In [2]:



    


from nltk.inference.resolution import *

Forma normal de Skolem

Para leer una expresión utilizamos Expression.fromstring, como lo vamos a utilizar mucho, le vamos a poner un nombre

  • all y exists segido de variable y un punto significan para todo y existe, respectivamente
  • las conectivas son & para el y, | para el o, -> para el implica, <-> para la equivalencia
  • la negación es - 




In [3]:



    


expr = Expression.fromstring

El comando skolemize encuentra una forma normal de Skolem





In [4]:



    


e=expr("all x.S(x)->exist z.all y. R(x,y)")
skolemize(e)



    


















    
Out[4]:








<OrExpression (-S(z1) | R(x,z2))>

Para reducir los contadores de las variables en esa expresión usamos normalize





In [5]:



    


_.normalize()



    


















    
Out[5]:








<OrExpression (-S(z3) | R(z3,z3))>

















In [6]:



    


e=expr("all x.(R(x,y)&-all y.R(x,y))")



    











In [7]:



    


s=skolemize(e).normalize()



    











In [8]:



    


print(s)



    


















    






(R(z2,z1) & -R(z2,F4(z2)))

Unificación

Dadas dos expresiones, most_general_unification proporciona un unificador más general

La salida es un diccionario con la substitución





In [9]:



    


e1=expr("F(x,y)")
e2=expr("F(a,F(b))")
most_general_unification(e1,e2)



    


















    
Out[9]:








{x: a, y: F(b)}

Cláusulas, forma clausular

El comando Clause aplicado a una lista de literales da como resultado una cláusula





In [10]:



    


Clause([e1,e2])



    


















    
Out[10]:








{F(x,y), F(a,F(b))}

También podemos utilizar clausify con una expresión obtenida previamente

Por ejemplo, si se lo aplicamos a $e=\forall x(R(x,y)\wedge \neg \forall y R(x,y))$, primero skolemiza y luego pasa a forma clausular





In [11]:



    


clausify(e)



    


















    
Out[11]:








[{R(z9,z8)}, {-R(z10,F6(z10))}]

















In [12]:



    


e=expr("all x.P(x)-> exists x.Q(x)")
clausify(e)



    


















    
Out[12]:








[{-P(z13), Q(z14)}]

Existe un error que impide usar predicados sin variables con ciertos comandos, tal y como se ha informado aquí





In [13]:



    


e=expr("Q|-Q")

El comando skolemize(e), y por tanto clausify(e) daría un error (que hemos omitido aquí)

Unificación y resolución

Las cláusulas tienen un método que permite calcular resolventes





In [14]:



    


c1=Clause([expr("P(x)"),expr("Q(a)")])
c2=Clause([expr("-P(a)")])



    











In [15]:



    


c1



    


















    
Out[15]:








{P(x), Q(a)}

















In [16]:



    


c2



    


















    
Out[16]:








{-P(a)}

















In [17]:



    


c1.unify(c2)



    


















    
Out[17]:








[{Q(a)}]

También podemos determinar si una cláusula es una tautología





In [18]:



    


c=clausify(expr("all x.(P(x)->P(x))"))
c



    


















    
Out[18]:








[{-P(z16), P(z16)}]

















In [19]:



    


c[0].is_tautology()



    


















    
Out[19]:








True

O si una cláusula es subcláusula (subsume) a otra





In [20]:



    


Clause([expr("P(x)")]).subsumes(Clause([expr("P(x)"), expr("Q(A)")]))



    


















    
Out[20]:








True

Demostraciones por resolución

Podemos utilizar ResolutionProverComman para realizar demostraciones por resolución





In [21]:



    


p1 = expr('humano(socrates)')
p2 = expr('all x.(humano(x) -> mortal(x))')
c  = expr('mortal(socrates)')
print(p1,", ",p2,", ",c)



    


















    






humano(socrates) ,  all x.(humano(x) -> mortal(x)) ,  mortal(socrates)

















In [22]:



    


demostracion =  ResolutionProverCommand(c, [p1,p2])



    











In [23]:



    


demostracion.prove()



    


















    
Out[23]:








True

















In [24]:



    


print(demostracion.proof())



    


















    






[1] {-mortal(socrates)}          A 
[2] {humano(socrates)}           A 
[3] {-humano(z18), mortal(z18)}  A 
[4] {-humano(socrates)}          (1, 3) 
[5] {mortal(socrates)}           (2, 3) 
[6] {}                           (1, 5)

Esta demostración nos indica que los tres primeros pasos son elementos de $\{p_1, p_2,\neg c\}$, que [4] es resolvente de 1 y 3, que [5] lo es de 2 y 3, y que finalmente se obtiene la cláusula vacía como resolvente de 1 y 5

Veamos otro ejemplo, ahora con funciones





In [25]:



    


h1=expr("all y.-R(A,y)")
h2=expr("all x.(-Q(x)|R(x,F(x)))")
c=expr("-Q(A)")



    











In [26]:



    


demostracion =  ResolutionProverCommand(c, [h1,h2])



    











In [27]:



    


demostracion.prove()



    


















    
Out[27]:








True

















In [28]:



    


print(demostracion.proof())



    


















    






[1] {Q(A)}                    A 
[2] {-R(A,z20)}               A 
[3] {-Q(z22), R(z22,F(z22))}  A 
[4] {R(A,F(A))}               (1, 3) 
[5] {-Q(A)}                   (2, 3) 
[6] {}                        (1, 5)

Ejemplo con error

Veamos ahora un ejemplo más complicado: $$\{ \forall y(-C(y)\to \exists x A(x,y)), \forall x(\exists y(-C(y)\wedge A(x,y))\to M(x)), \forall x(D(x)\to M(x)), \forall x((M(x)\wedge D(x))\to \neg(\exists y(\neg C(y)\wedge A(x,y)))), \exists x\neg C(x)\}\models \exists x(M(x)\wedge \neg D(x)) $$





In [29]:



    


a=expr("exists x.(M(x)&-D(x))")



    











In [30]:



    


print(a)



    


















    






exists x.(M(x) & -D(x))

















In [31]:



    


h1=expr("all y.(-C(y)->exists x.A(x,y))")
h2=expr("all x.(exists y.(-C(y)&A(x,y))->M(x))")
h3=expr("all x.(D(x)->M(x))")
h4=expr("all x.((M(x)&D(x))->-(exists y.(-C(y)&A(x,y))))")
h5=expr("exists x.-C(x)")



    











In [32]:



    


demostracion =  ResolutionProverCommand(a, [h1,h2,h3,h4,h5])



    











In [33]:



    


demostracion.prove()



    


















    
Out[33]:








True

















In [34]:



    


print(demostracion.proof())



    


















    






[1] {-M(z24), D(z24)}                        A 
[2] {C(z27), A(F25(z27),z27)}                A 
[3] {C(z30), -A(z31,z30), M(z31)}            A 
[4] {-D(z33), M(z33)}                        A 
[5] {-M(z37), -D(z37), C(z36), -A(z37,z36)}  A 
[6] {-C(z39)}                                A 
[7] {C(z30), -A(z31,z30), D(z31)}            (1, 3) 
[8] {}                                       (1, 4)

Si observamos la demostración que nos proporciona este comando, vemos que de [1] y [4] ha obtenido la cláusula vacía, cosa que no es posible. Algo va mal. Veamos si podemos acotar mejor el error. Para ello tomemos el siguiente conjunto de fórmulas





In [35]:



    


h = Expression.fromstring("all x.(P(x) | Q(x))")
t= Expression.fromstring("all x.(-P(x) | -Q(x))")
s = Expression.fromstring("exists x.R(x)")
demostracion=ResolutionProverCommand(s,[h,t])



    











In [36]:



    


demostracion.prove()



    


















    
Out[36]:








True

















In [37]:



    


print(demostracion.proof())



    


















    






[1] {-R(z41)}           A 
[2] {P(z43), Q(z43)}    A 
[3] {-P(z45), -Q(z45)}  A 
[4] {}                  (2, 3)

Una vez más vemos que deduce la cláusula vacía como resolvente de [2] y [3], lo cual no es posible

Veamos cómo hace la resolvente en estos casos





In [38]:



    


c=Clause([expr("P(x)"),expr("Q(x)")])
cn=Clause([expr("-P(x)"),expr("-Q(x)")])



    











In [39]:



    


c.unify(cn)



    


















    
Out[39]:








[{}]

Lo cual es claramente erróneo

Demostración usando Tablau





In [40]:



    


demostracion = TableauProverCommand(s,[h,t])



    











In [41]:



    


demostracion.prove()



    


















    
Out[41]:








False

















In [42]:



    


print(demostracion.proof())



    


















    






-exists x.R(x)
   all x.(-P(x) | -Q(x)):   []
         --> Using 'z46'
      (-P(z46) | -Q(z46))
         -P(z46)
            all x.(-P(x) | -Q(x)):   [z46]
                  --> Variables Exhausted
               all x.-R(x):   []
                     --> Using 'z46'
                  -R(z46)
                     all x.(-P(x) | -Q(x)):   [z46]
                           --> Variables Exhausted
                        all x.-R(x):   [z46]
                              --> Variables Exhausted
                           all x.(P(x) | Q(x)):   []
                                 --> Using 'z46'
                              (P(z46) | Q(z46))
                                 P(z46)
                                    CLOSED
                                 Q(z46)
                                    all x.(-P(x) | -Q(x)):   [z46]
                                          --> Variables Exhausted
                                       all x.-R(x):   [z46]
                                             --> Variables Exhausted
                                          all x.(P(x) | Q(x)):   [z46]
                                                --> Variables Exhausted
                                             AGENDA EMPTY

















In [43]:



    


h1=expr("all y.(-C(y)->exists x.A(x,y))")
h2=expr("all x.(exists y.(-C(y)&A(x,y))->M(x))")
h3=expr("all x.(D(x)->M(x))")
h4=expr("all x.((M(x)&D(x))->-(exists y.(-C(y)&A(x,y))))")
h5=expr("exists x.-C(x)")
a=expr("exists x.(M(x)&-D(x))")



    











In [44]:



    


demostracion = TableauProverCommand(a,[h1,h2,h3,h4,h5])

Por desgracia demostracion.prove() demora más de lo deseado





In [45]:



    


h1=expr("all y.-R(A,y)")
h2=expr("all x.(-Q(x)|R(x,F(x)))")
c=expr("-Q(A)")
demostracion = TableauProverCommand(c,[h1,h2])



    











In [46]:



    


demostracion.prove()



    


















    






---------------------------------------------------------------------------
RecursionError                            Traceback (most recent call last)
<ipython-input-46-bbe735c152ec> in <module>()
----> 1 demostracion.prove()

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/api.py in prove(self, verbose)
    276             self._result, self._proof = self._prover._prove(self.goal(),
    277                                                             self.assumptions(),
--> 278                                                             verbose)
    279         return self._result
    280 

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _prove(self, goal, assumptions, verbose)
     51                     print(e)
     52                 else:
---> 53                     raise e
     54         return (result, '\n'.join(debugger.lines))
     55 

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _prove(self, goal, assumptions, verbose)
     43             agenda.put_all(assumptions)
     44             debugger = Debug(verbose)
---> 45             result = self._attempt_proof(agenda, set(), set(), debugger)
     46         except RuntimeError as e:
     47             if self._assume_false and str(e).startswith('maximum recursion depth exceeded'):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_d_neg(self, current, context, agenda, accessible_vars, atoms, debug)
    185     def _attempt_proof_d_neg(self, current, context, agenda, accessible_vars, atoms, debug):
    186         agenda.put(current.term.term, context)
--> 187         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    188 
    189     def _attempt_proof_n_all(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    215         new_agenda.put(current.second, context)
    216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
--> 217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 
    219     def _attempt_proof_imp(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    102             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    103             agenda.mark_alls_fresh();
--> 104             return self._attempt_proof(agenda, accessible_vars|set(current.args), atoms|set([(current, False)]), debug+1)
    105 
    106     def _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_or(self, current, context, agenda, accessible_vars, atoms, debug)
    214         agenda.put(current.first, context)
    215         new_agenda.put(current.second, context)
--> 216         return self._attempt_proof(agenda, accessible_vars, atoms, debug+1) and \
    217                 self._attempt_proof(new_agenda, accessible_vars, atoms, debug+1)
    218 

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
--> 285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    286 
    287             else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_n_atom(self, current, context, agenda, accessible_vars, atoms, debug)
    118             #mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
    119             agenda.mark_alls_fresh();
--> 120             return self._attempt_proof(agenda, accessible_vars|set(current.term.args), atoms|set([(current.term, True)]), debug+1)
    121 
    122     def _attempt_proof_prop(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    290                 current._exhausted = True
    291                 agenda[Categories.ALL].add((current,context))
--> 292                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)
    293 
    294         else:

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof(self, agenda, accessible_vars, atoms, debug)
     86 
     87         debug.line((current, context))
---> 88         return proof_method(current, context, agenda, accessible_vars, atoms, debug)
     89 
     90     def _attempt_proof_atom(self, current, context, agenda, accessible_vars, atoms, debug):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in _attempt_proof_all(self, current, context, agenda, accessible_vars, atoms, debug)
    281                 debug.line('--> Using \'%s\'' % variable_to_use, 2)
    282                 current._used_vars |= set([variable_to_use])
--> 283                 agenda.put(current.term.replace(current.variable, variable_to_use), context)
    284                 agenda[Categories.ALL].add((current,context))
    285                 return self._attempt_proof(agenda, accessible_vars, atoms, debug+1)

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/inference/tableau.py in put(self, expression, context)
    371         else:
    372             ex_to_add = expression
--> 373         self.sets[self._categorize_expression(ex_to_add)].add((ex_to_add, context))
    374 
    375     def put_all(self, expressions):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __hash__(self)
    941 
    942     def __hash__(self):
--> 943         return hash(repr(self))
    944 
    945     def substitute_bindings(self, bindings):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __repr__(self)
   1071 
   1072     def __repr__(self):
-> 1073         return '<%s %s>' % (self.__class__.__name__, self)
   1074 
   1075     def __str__(self):

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1673 
   1674     def __str__(self):
-> 1675         return Tokens.NOT + "%s" % self.term
   1676 
   1677 

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in <genexpr>(.0)
   1253         if self.is_atom():
   1254             function, args = self.uncurry()
-> 1255             arg_str = ','.join("%s" % arg for arg in args)
   1256         else:
   1257             #Leave arguments curried

/Users/pedro/lib/anaconda/lib/python3.5/site-packages/nltk/sem/logic.py in __str__(self)
   1383 
   1384     def __str__(self):
-> 1385         return "%s" % self.variable
   1386 
   1387 class IndividualVariableExpression(AbstractVariableExpression):

RecursionError: maximum recursion depth exceeded while calling a Python object

Demostraciones con prover9

Por suerte, nltk ofrece una interfaz a prover9 que parece ser rápida y correcta





In [49]:



    


h1=expr("all y.(-C(y)->exists x.A(x,y))")
h2=expr("all x.(exists y.(-C(y)&A(x,y))->M(x))")
h3=expr("all x.(D(x)->M(x))")
h4=expr("all x.((M(x)&D(x))->-(exists y.(-C(y)&A(x,y))))")
h5=expr("exists x.-C(x)")
a=expr("exists x.(M(x)&-D(x))")



    











In [50]:



    


demostracion = Prover9Command(a,[h1,h2,h3,h4,h5])



    











In [51]:



    


demostracion.prove()



    


















    
Out[51]:








True

















In [52]:



    


print(demostracion.proof())



    


















    






============================== prooftrans ============================
Prover9 (64) version 2009-11A, November 2009.
Process 30475 was started by pedro on MacBook-Pro-de-Pedro.local,
Thu May 12 17:52:50 2016
The command was "/Users/pedro/lib/LADR-2009-11A/bin/prover9".
============================== end of head ===========================

============================== end of input ==========================

============================== PROOF =================================

% -------- Comments from original proof --------
% Proof 1 at 0.00 (+ 0.00) seconds.
% Length of proof is 17.
% Level of proof is 5.
% Maximum clause weight is 3.000.
% Given clauses 0.


1 (all x (-C(x) -> (exists y A(y,x)))).  [assumption].
2 (all x ((exists y (-C(y) & A(x,y))) -> M(x))).  [assumption].
4 (all x (M(x) & D(x) -> -(exists y (-C(y) & A(x,y))))).  [assumption].
5 (exists x -C(x)).  [assumption].
6 (exists x (M(x) & -D(x))).  [goal].
7 -C(c1).  [clausify(5)].
8 C(x) | A(f1(x),x).  [clausify(1)].
9 C(x) | -A(y,x) | M(y).  [clausify(2)].
10 -M(x) | -D(x) | C(y) | -A(x,y).  [clausify(4)].
11 -M(x) | D(x).  [deny(6)].
13 -M(x) | -D(x) | -A(x,c1).  [resolve(7,a,10,c)].
14 -A(x,c1) | M(x).  [resolve(7,a,9,a)].
15 A(f1(c1),c1).  [resolve(7,a,8,a)].
16 -M(x) | -A(x,c1) | -M(x).  [resolve(13,b,11,b)].
17 M(f1(c1)).  [resolve(14,a,15,a)].
18 -M(f1(c1)) | -M(f1(c1)).  [resolve(16,b,15,a)].
19 $F.  [copy(18),merge(b),unit_del(a,17)].

============================== end of proof ==========================

Content source: pedritomelenas/LMD

Similar notebooks:

notebook.community | gallery | about