Limit for gsl_sf_gamma_inc

[Jackson Vanover]

Using version 2.6 of GSL from ftp://ftp.gnu.org/gnu/gsl/gsl-2.6.tar.gz

OS is Ubuntu 18.04.2 LTS

Hardware is a Dell workstation with a 3.60 GHz Intel i7-4790 and 32 GB
of RAM

Compiler is gcc 7.4.0 with the -w option

When evaluating gsl_sf_gamma_inc(x, inf) where x is some floating point
number, a NaN is returned even though the limit approaches 0. I bring this
up as an issue because in other cases, the special functions in the library
handle such limits approaching infinity properly, e.g. gsl_sf_eta(inf)
returns 1.

#include <gsl/gsl_sf.h>
#include <stdio.h>
#include <gsl/gsl_math.h>

int main (void){
double out;
out = gsl_sf_gamma_inc(2.533265554575144, GSL_POSINF);

printf("%f\n", out);
printf("%.21e\n", out);
return 0;
}

Best,
Jackson Vanover
Best,
Jackson Vanover