Hi, I found that gsl_sf_psi_n_e yields a domain error for negative non-integer input, for example n=2 and x=-0x1.fffffcffffffep+22, whereas the function is perfectly defined. For example Wolfram alpha yields 124.025 :
https://www.wolframalpha.com/input?i=polygamma%282%2C-4503599224717311%2F536870912%29 #include <stdio.h> #include <gsl/gsl_sf.h> int main () { gsl_sf_result ret; int n = 2; double x = -0x1.fffffcffffffep+22; gsl_sf_psi_n_e (n, x, &ret); } $ gcc -I/tmp/include -L/tmp/lib /tmp/e.c -lgsl -lgslcblas $ ./a.out gsl: psi.c:781: ERROR: domain error Default GSL error handler invoked. Aborted (core dumped) ./a.out Best regards, Paul
