fpclassify - cppreference.com (original) (raw)

| | | | | ------------------------------------------------------ | | ----------- | | #define fpclassify(arg) /* implementation defined */ | | (since C99) |

Categorizes floating-point value arg into the following categories: zero, subnormal, normal, infinite, NAN, or implementation-defined category. 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: a normal long double value might become subnormal when converted to double and zero when converted to float.

[edit] Parameters

arg - floating-point value

[edit] Return value

One of FP_INFINITE, FP_NAN, FP_NORMAL, FP_SUBNORMAL, FP_ZERO or implementation-defined type, specifying the category of arg.

[edit] Example

#include <float.h> #include <math.h> #include <stdio.h>   const char* show_classification(double x) { switch(fpclassify(x)) { case FP_INFINITE: return "Inf"; case FP_NAN: return "NaN"; case FP_NORMAL: return "normal"; case FP_SUBNORMAL: return "subnormal"; case FP_ZERO: return "zero"; default: return "unknown"; } }   int main(void) { printf("1.0/0.0 is %s\n", show_classification(1 / 0.0)); printf("0.0/0.0 is %s\n", show_classification(0.0 / 0.0)); printf("DBL_MIN/2 is %s\n", show_classification(DBL_MIN / 2)); printf("-0.0 is %s\n", show_classification(-0.0)); printf("1.0 is %s\n", show_classification(1.0)); }

Output:

1.0/0.0 is Inf 0.0/0.0 is NaN DBL_MIN/2 is subnormal -0.0 is zero 1.0 is normal

[edit] References

[edit] See also