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) |
#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
|
(C99) | classifies the given floating-point value (function macro) |
C++ documentation for FP_categories |
|
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