[Help-gsl] wrong results of the function gsl_cdf_ugaussian_Pinv

[Dafna Hirschfeld]

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

int main(){
    double x= 0.5;
    double res = gsl_cdf_ugaussian_Pinv(x);
    printf("icdf(%f)=%f\n",x,res);
    return 0;
}

For some reason the output is: *icdf(0.500000)=1.000000*

Which is wrong, it should be: *icdf(0.500000)=0.000000 (because P(X<0)=0.5)*

Did I do something wrong?