Test for not-a-number (NaN)
#include <math.h> #define isnan ( x ) ...
The isnan() macro determines if x is Not-A-Number (NaN).
#include <stdio.h> #include <stdlib.h> #include <math.h> int main(int argc, char** argv) { double a, b, c, d; a = 2; b = -0.5; c = NAN; d = 1.0/0.0; printf("%f is %s \n", a, (isnan(a)) ? "not a number" : "a number"); printf("%f is %s \n", b, (isnan(b)) ? "not a number" : "a number"); printf("%f is %s \n", c, (isnan(c)) ? "not a number" : "a number"); printf("%f is %s \n", d, (isnan(d)) ? "not a number" : "a number"); return EXIT_SUCCESS; }
produces the output:
2.000000 is a number -0.500000 is a number nan is not a number inf is a number
Safety: | |
---|---|
Cancellation point | No |
Interrupt handler | No |
Signal handler | No |
Thread | Yes |