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× C Standard Library

The C <math.h> isinf() macro returns true if the given argument is an infinity value (either positive infinity or negative infinity), else returns false.




x Specify a floating-point value.

Return Value

Returns true (non-zero value) if the argument is an infinity value, else returns false (zero value).


The below example shows the usage of isinf() macro.

#include <stdio.h>
#include <math.h>
int main (){

  printf("isinf(10.5): %d\n", isinf(10.5));
  printf("isinf(1.0/0.0): %d\n", isinf(1.0/0.0));
  printf("isinf(-1.0/0.0): %d\n", isinf(-1.0/0.0));
  printf("isinf(sqrt(-1.0)): %d\n", isinf(sqrt(-1.0)));
  return 0;

The output of the above code will be:

isinf(10.5): 0
isinf(1.0/0.0): 1
isinf(-1.0/0.0): -1
isinf(sqrt(-1.0)): 0

❮ C <math.h> Library