[Maxima-bugs] makefact converts gamma functions that contain imaginary values
Subject: [Maxima-bugs] makefact converts gamma functions that contain imaginary values
From: Raymond Toy
Date: Wed, 16 Jan 2013 09:22:25 -0800
On Tue, Jan 15, 2013 at 10:59 PM, Joal Heagney <joalheagney at gmail.com>wrote:
> Hi Raymond,
> I've tried it again using gamma(3+%i) (Man has it been a long time since I
> used maxima directly), and it gives the same behaviour (except (%i + 2)! of
> course).
>
> The issue is that in sagemath, we're using the makefact function to
> simplify some gamma/binomial expressions, but when gamma(x+1) isn't a
> positive integer, x! is supposed to be mathematically meaningless.
>
> Hmmm, except that I just tried:
> (%i2) float((%i + 3)!);
> (%o2) 4.980156681183563 %i + 1.5494982830181063
>
> so it looks like I have to go back to the sage team and let them know that
> maxima seems to treat ! as a gamma function equivalent, while sagemath
> doesn't.
>
>
>
Please use the maxima mailing list and not the maxima-bugs list.
I'm glad you found the issue. Looks like you have several alternatives.
Tell sagemath that ! is defined for the almost all complex numbers,
implement a new version of makefact that only does the transformations you
want, or tell sagemath to use something other than ! to get the factorial
function that's defined only on positive integers.
Ray