C/math.h/isinf
int isinf(fpval): Returns nonzero if fpval is infinite
#include <stdio.h>
#include <math.h>
int main(void)
{
printf("isinf(-1.0) %d\n", isinf(-1.0));
printf("isinf(1.0) %d\n", isinf(1.0));
printf("isinf(1.0/0.0) %d\n", isinf(1.0/0.0));
return 0;
}
/*
isinf(-1.0) 0
isinf(1.0) 0
isinf(1.0/0.0) 1
*/