FP_NORMAL, FP_SUBNORMAL, FP_ZERO, FP_INFINITE, FP_NAN (original) (raw)
| Defined in header <math.h> | | | | -------------------------------------------------------------------- | | ----------- | | #define FP_NORMAL /*implementation defined*/ | | (since C99) | | #define FP_SUBNORMAL /*implementation defined*/ | | (since C99) | | #define FP_ZERO /*implementation defined*/ | | (since C99) | | #define FP_INFINITE /*implementation defined*/ | | (since C99) | | #define FP_NAN /*implementation defined*/ | | (since C99) |
The FP_NORMAL, FP_SUBNORMAL, FP_ZERO, FP_INFINITE, FP_NAN macros each represent a distinct category of floating-point numbers. They all expand to an integer constant expression.
| Constant | Explanation |
|---|---|
| FP_NORMAL | indicates that the value is normal, i.e. not an infinity, subnormal, not-a-number or zero |
| FP_SUBNORMAL | indicates that the value is subnormal |
| FP_ZERO | indicates that the value is positive or negative zero |
| FP_INFINITE | indicates that the value is not representable by the underlying type (positive or negative infinity) |
| FP_NAN | indicates that the value is not-a-number (NaN) |
[edit] Example
#include <stdio.h> #include <math.h> #include <float.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
C17 standard (ISO/IEC 9899:2018):
7.12/6 FP_NORMAL, ... (p: 169-170)
C11 standard (ISO/IEC 9899:2011):
7.12/6 FP_NORMAL, ... (p: 232)
C99 standard (ISO/IEC 9899:1999):
7.12/6 FP_NORMAL, ... (p: 213)