[Python-3000] adding gamma and error functions to math module

[Raymond Hettinger]

From: "nirinA raseliarison" <nirina at mail.blueline.mg>
>> >>> from test.test_random import gamma
 . . .
> there is a simple implementation in Python at:
> http://en.wikipedia.org/wiki/Lanczos_approximation
> with coefficients slightly different from those in
> test_random.py, one gets:
 . . .
> with the gamma from gcc under linux,
> which uses the MPFR library,
> the result is not really satisfying:
> using the code from numerical recipes chap 6:
 . . .
> 
> and from the scipy package,
> which uses the cephes math library:
 ...
> i'll check if an appropriate choice of
> of a set of coefficients or extending the
> number of coefficients can lead to a more
> accurate result.

Discussions of "my approximation is better/faster/etc than yours" can be interminable.
Recommend you put together your favorite approximation in a recipe.
The one in test.random is suffices well for its purpose.


Raymond