Incorrect value returned by hyp1f1() (Trac #914)

[scipy-gitbot]

Original ticket http://projects.scipy.org/scipy/ticket/914 on 2009-04-06 by trac user lckarssen, assigned to unknown.

I tried to use special.assoc_laguerre(x,n,k) today and noticed that it returns 0.0 for n=0. However, it should return 1.0 (I used Mathematica to verify as well as a textbook).
Looking at the code, I noticed that special.hyp1f1(a,b,x) which is called by assoc_laguerre() returns 0.0 for a=0, whereas it should return 1.0 (only verified by Mathematica). I tried to look for the code of hyp1f1(), but couldn't find it.

Furthermore, I noticed that assoc_laguerre() doesn't have a docstring explaining it's usage. It might be nice to at least point to special.laguerre().

The tests were done on a 32bit install of Ubuntu 8.10, which ships scipy 0.6.0

[scipy-gitbot]

@pv wrote on 2009-04-07

Duplicate of gh-1314, gh-992