The argument x must not be exactly zero or a negative integer, or is undefined. Also, x must not be too close to a negative integer such that the accuracy of the result is less than half precision. If no value can be computed, then NaN is returned.
Example
In this example, is evaluated.
#include <imsl.h>
#include <stdio.h>
int main(){
float x=1.915, ans;
ans=imsl_f_psi(x);
printf("psi(%f) = %f\n", x, ans);
}
Output
psi(1.915000) = 0.366452
Warning Errors
IMSL_NEAR_NEG_INT_WARN
The result is accurate to less than one-half precision because “x” is too close to a negative integer.
