On Tue, 22 Nov 2011 11:56:51 +0100 Florent Hivert <florent.hiv...@lri.fr> wrote:
> > > > method. Thanks to Cython, this is very easy. However, Maxima and > > > Ginac have a different semantic for those two functions: > > > > > > - Maxima: Does not change the expression; if the expression is > > > not a quotient, then this will return the expression itself. > > > - Ginac: try to normalize the expression to put it in the form > > > N/D and then return N; > > > > > > For example, with an expression such as "x + y/(x + 2)", > > > > > > - Maxima: numer = x + y/(x + 2), denom = 1 > > > - Ginac: numer = (x^2 + 2x + y), denom = x + 2 > > > > > > I can more or less emulate Maxima's behavior with Ginac, but I'm > > > not sure what's best to do. I see several options: > > > > > > 1 - Forget about Maxima and follows Ginac semantic; > > > 2 - Follows Maxima semantic as close as possible using Ginac; > > > 3 - Have a parameter 'algorithm' to select the needed one. > > > Depending one the algorithm the semantic differ; > > > 4 - Have a parameter 'normal' to select if we normalize or nor > > > the result before computing the numerator, always use Ginac > > > however. 5 - 3 and 4, have two parameters, one for selecting > > > Maxima or Ginac, one for performing a normalization before. > > > 6 - other options ??? > > > > > > In case 3, 4, 5, we also should decide what is the default. > > > > > > What do you think ? > > > > I like 4 best, though I suggest calling the parameter 'normalize.' > > > > How do you plan to handle normalize=False? I suggest > > > > if the expression is not a mul: > > return self > > else: > > separate the positive and negative exponents > > This is indeed what I had in mind. I don't recall a pynac function which separates negative and positive exponents in a mul. There is some code for this in mul::do_print_rat_func() (in Pynac). Maybe we should move that to a new function. How do you do this ATM? AFAIK, you can't access the expairseq stored in a mul from Cython. > Any idea for the default for normalize ? IHMO, True. The response you get when it's false is nonsense in most cases. If you want that behavior, you should state that you know what you are doing by passing normalize=False. Cheers, Burcin -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
