I might have misunderstood your suggestion, but I don't think that it is
the solution (I tried it and I get the same problem).
My problem is that when I try the same expansion several times in a row,
the list is not cleared after each call and thus the coefficients are false:
sage: M=FreeMonoid(2,'x,y')
sage: to_pbw(pbw_element(M.1))
{word: y: 1}
sage: to_pbw(pbw_element(M.1))
{word: y: 2}
sage: to_pbw(pbw_element(M.1))
{word: y: 3}
Thanks anyway!
Le samedi 29 juin 2013 12:42:31 UTC+2, Mike Hansen a écrit :
>
> I'm guessing this is just due to you using dict() in the function
> definition. See http://effbot.org/zone/default-values.htm . If you
> replace it with None do something like
>
> if l is None:
> l = {}
>
> at the beginning of the function, then things should be okay.
>
> --Mike
> --Mike
>
>
> On Sat, Jun 29, 2013 at 11:29 AM, Matthieu Deneufchâtel
> <[email protected] <javascript:>> wrote:
> > In a recursive function, I use a dictionary (which contains the elements
> of
> > the expansion of the argument on another basis). Since each call to the
> > function needs the dictionary, I don't want the user to be forced to put
> the
> > dictionary as an argument (i.e. I want him to call to_pbw(elem) instead
> of
> > to_pbw(elem,{})). But I get a little confused between local and global
> > variables with the code below since the dictionary is not emptied when
> > needed (my function as the expected behavior only when I call
> > to_pbw(elem,{})).
> >
> > Could anyone help me (provided my question is not unclear)?
> > Matthieu
> >
> > def to_pbw(f,l=dict()):
> > from sage.combinat.words.finite_word import to_monoid_element
> > if f!= 0 * f.parent().one():
> > support = [to_word(i[1]) for i in list(f)]
> > min=support[0]
> > if len(support) > 1:
> > for word in support[1:len(support)-1]:
> > if min.lex_less(word):
> > min = word
> > coeff = list(f)[support.index(min)][0]
> > if min not in l.keys():
> > l[min]=coeff
> > else:
> > l[min] += coeff
> > remainder = f - coeff * pbw_element(to_monoid_element(min))
> > return to_pbw(remainder,l)
> > return l
> >
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