

In [1]:

    
import spot
spot.setup()

Let's build a small automaton to use as example.



In [2]:

    
aut = spot.translate('G(Fa <-> Xb)'); aut









    Out[2]:

Build an accepting run:



In [3]:

    
run = aut.accepting_run(); run









    Out[3]:





Prefix:
  0
  |  !a
Cycle:
  1
  |  a & b	{0}
  2
  |  !a & b

Accessing the contents of the run can be done via the prefix and cycle lists.



In [4]:

    
print(spot.bdd_format_formula(aut.get_dict(), run.prefix[0].label))
print(run.cycle[0].acc)









    



!a
{0}

To convert the run into a word, using spot.twa_word(). Note that our runs are labeled by Boolean formulas that are not necessarily a conjunction of all involved litterals. The word is just the projection of the run on its labels.



In [5]:

    
word = spot.twa_word(run); word









    Out[5]:





!a; cycle{a & b; !a & b}

Accessing the different formulas (stored as BDDs) can be done again via the prefix and cycle lists.



In [6]:

    
print(spot.bdd_format_formula(aut.get_dict(), word.prefix[0]))
print(spot.bdd_format_formula(aut.get_dict(), word.cycle[0]))
print(spot.bdd_format_formula(aut.get_dict(), word.cycle[1]))









    



!a
a & b
!a & b

Calling simplifify() will produce a shorter word that is compatible with the original word. For instance in the above word, the initial !a is compatible with both a & b and !a & b. The word obtained by restricting !a to !a & b is therefore still accepted, but it allows removing the prefix by rotating the cycle:



In [7]:

    
word.simplify()
word









    Out[7]:





cycle{!a & b; a & b}

Such a simplified word can be created directly from the automaton:



In [8]:

    
aut.accepting_word()









    Out[8]:





cycle{!a & b; a & b}

Words can be created using the parse_word function:



In [9]:

    
print(spot.parse_word('a; b; cycle{a&b}'))
print(spot.parse_word('cycle{a&bb|bac&(aaa|bbb)}'))
print(spot.parse_word('a; b;b; qiwuei;"a;b&c;a" ;cycle{a}'))









    



a; b; cycle{a & b}
cycle{(a & bb) | (aaa & bac) | (bac & bbb)}
a; b; b; qiwuei; "a;b&c;a"; cycle{a}



In [10]:

    
# make sure that we can parse a word back after it has been printed
spot.parse_word(str(spot.parse_word('a;b&a;cycle{!a&!b}')))









    Out[10]:





a; a & b; cycle{!a & !b}

Words can be easily converted as automata



In [11]:

    
w1 = spot.parse_word('a; !a; cycle{a; !a; a}')



In [12]:

    
w1.as_automaton()









    Out[12]:

The rest of this pages tests some syntax errors, you (humans) may skip it, but the test suite will not.



In [13]:

    
print(spot.parse_word('a; b&!a; b'))









    



  File "<string>", line unknown
SyntaxError: 
>>> a; b&!a; b
              ^
A twa_word must contain a cycle



In [14]:

    
print(spot.parse_word('a; b; c}'))









    



  File "<string>", line unknown
SyntaxError: 
>>> a; b; c}
           ^
Expected ';' delimiter: '}' stands for ending a cycle



In [15]:

    
print(spot.parse_word('a; cycle{}'))









    



  File "<string>", line unknown
SyntaxError: 
>>> a; cycle{}
             ^
empty input



In [16]:

    
print(spot.parse_word('a; cycle{!a}; a'))









    



  File "<string>", line unknown
SyntaxError: 
>>> a; cycle{!a}; a
                ^
Input should be finished after cycle



In [17]:

    
# Creating an empty word is OK...
w = spot.twa_word(spot._bdd_dict)



In [18]:

    
# ... as long as this word is not printed.
print(w)









    



---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)
<ipython-input-18-971829bb8f5f> in <module>()
      1 # ... as long as this word is not printed.
----> 2 print(w)

/home/adl/git/spot/python/spot/impl.py in __str__(self)
   3599 
   3600     def __str__(self) -> "std::string":
-> 3601         return _impl.twa_word___str__(self)
   3602 twa_word_swigregister = _impl.twa_word_swigregister
   3603 twa_word_swigregister(twa_word)

RuntimeError: a twa_word may not have an empty cycle