`expression``.sum(``exp``)`

`expression` + `exp`

An expression which denotes the sum (or disjunction) of both series.

Preconditions:



In [1]:

    
import vcsn
ctx = vcsn.context('lal_char, q')
exp = lambda e: ctx.expression(e)
exp('a*b') + exp('ab*')









    














    Out[1]:





$a \, {b}^{*} + {a}^{*} \, b$

Of course, trivial identities are applied.



In [2]:

    
exp('<2>a') + exp('<3>a')









    Out[2]:





$ \left\langle 5 \right\rangle \,a$



In [3]:

    
exp('<2>a') + exp('\z')









    Out[3]:





$ \left\langle 2 \right\rangle \,a$