fpclassify
| Defined in header <math.h>
|
||
| #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.
Parameters
| arg | - | floating point value |
Return value
One of FP_INFINITE, FP_NAN, FP_NORMAL, FP_SUBNORMAL, FP_ZERO or implementation-defined type, specifying the category of arg.
Example
Run this code
#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
References
- C11 standard (ISO/IEC 9899:2011):
- 7.12.3.1 The fpclassify macro (p: 235)
- C99 standard (ISO/IEC 9899:1999):
- 7.12.3.1 The fpclassify macro (p: 216)
See also
| (C99) |
checks if the given number has finite value (function) |
| (C99) |
checks if the given number is infinite (function) |
| (C99) |
checks if the given number is NaN (function) |
| (C99) |
checks if the given number is normal (function) |