isinf

#define isinf(arg) /* implementation defined */

Determines if the given floating-point number arg is positive or negative infinity. The macro returns an integral value.

FLT_EVAL_METHOD is ignored: even if the argument is evaluated with more range and precision than its type, it is first converted to its semantic type, and the classification is based on that.

Parameters

Return value

Nonzero integral value if arg has an infinite value, ​0​ otherwise.

Example

#include <stdio.h>
#include <math.h>
#include <float.h>
 
int main(void)
{
    printf("isinf(NAN)         = %d\n", isinf(NAN));
    printf("isinf(INFINITY)    = %d\n", isinf(INFINITY));
    printf("isinf(0.0)         = %d\n", isinf(0.0));
    printf("isinf(DBL_MIN/2.0) = %d\n", isinf(DBL_MIN/2.0));
    printf("isinf(1.0)         = %d\n", isinf(1.0));
    printf("isinf(exp(800))    = %d\n", isinf(exp(800)));
}

isinf(NAN)         = 0
isinf(INFINITY)    = 1
isinf(0.0)         = 0
isinf(DBL_MIN/2.0) = 0
isinf(1.0)         = 0
isinf(exp(800))    = 1

References

• C17 standard (ISO/IEC 9899:2018):
• 7.12.3.3 The isinf macro (p: 172)
• C11 standard (ISO/IEC 9899:2011):
• 7.12.3.3 The isinf macro (p: 236)
• C99 standard (ISO/IEC 9899:1999):
• 7.12.3.3 The isinf macro (p: 217)

See also