/C

# isfinite

Defined in header `<math.h>`
`#define isfinite(arg) /* implementation defined */`
(since C99)

Determines if the given floating point number `arg` has finite value i.e. it is normal, subnormal or zero, but not infinite or NaN. 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

 arg - floating point value

### Return value

Nonzero integral value if `arg` has finite value, `​0​` otherwise.

### Example

```#include <stdio.h>
#include <math.h>
#include <float.h>

int main(void)
{
printf("isfinite(NAN)         = %d\n", isfinite(NAN));
printf("isfinite(INFINITY)    = %d\n", isfinite(INFINITY));
printf("isfinite(0.0)         = %d\n", isfinite(0.0));
printf("isfinite(DBL_MIN/2.0) = %d\n", isfinite(DBL_MIN/2.0));
printf("isfinite(1.0)         = %d\n", isfinite(1.0));
printf("isfinite(exp(800))    = %d\n", isfinite(exp(800)));
}```

Possible output:

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

### References

• C11 standard (ISO/IEC 9899:2011):
• 7.12.3.2 The isfinite macro (p: 236)
• C99 standard (ISO/IEC 9899:1999):
• 7.12.3.2 The isfinite macro (p: 216-217)