problem with gsl_sf_lnpoch

[Giulio Bottazzi <giulio dot bottazzi at libero dot it>]

Hi,
It seems that the exponential of the logarithm of the Pochhammer symbol
with second argument equal to zero is NOT one. Consider the following
little program, which should print two times the number 1 separated by
a space

/* -- START test.c */
#include <stdio.h>
#include <math.h>
#include <gsl/gsl_sf_gamma.h>
int main(){

  printf("exp(log(poch))=%g poch=%g\n",
        exp( gsl_sf_lnpoch(7,0)),gsl_sf_poch(7,0));

  return 0;
}
/* -- END test.c */

If I compile it with
#gcc -Wall test.c -lgsl -lgslcblas -lm -o test
and run
#./test
I get:
#exp(log(poch))=2.71828 poch=1

What's going on? I can't see any mistake in my code.

Best,
	Giulio.


--
Giulio Bottazzi                       PGP Key ID:BAB0A33F
giulio.bottazzi@libero.it   http://www.sssup.it/~bottazzi

Attachment: pgp00000.pgp
Description: PGP signature