Le dimanche 09 août 2009 à 01:31 -0600, Ondrej Certik a écrit : > On Sun, Aug 9, 2009 at 1:25 AM, Luke<hazelnu...@gmail.com> wrote: > > Attached is a patch that allows expand to handle negative integer > > powers. This effectively allows expressions like: > > expr = (x+y)**(-2) > > to be expanded by calling > > expr.expand() > > Thanks, it's in. > > Ondrej
I have a few comments: * The call to expand() is slow and unnecessary. At this stage, all that's needed is to call _eval_expand_multinomial(deep=False). So instead of: + return 1 / Pow(base, -exp.p).expand(deep=deep, **hints) we should have: + return 1 / Pow(base, -exp.p)._eval_expand_multinomial(deep=False) * This line suggests that it would be helpful to create an 'inverse' property - less work is needed to create this inverse than for a generic Pow instance. * There should be more tests for negative exponents, basically duplicating all existing tests with positive exponents *I don't see the point of the third test: it's only testing that (x +y)**2*(x+y)**-4 == (x+y)**-2 which isn't related to expand. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "sympy-patches" group. To post to this group, send email to sympy-patches@googlegroups.com To unsubscribe from this group, send email to sympy-patches+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sympy-patches?hl=en -~----------~----~----~----~------~----~------~--~---
