fpclassify
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fpclassify
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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.
[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
Run this code
#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
- C23 standard (ISO/IEC 9899:2024):
- 7.12.3.1 The fpclassify macro (p: TBD)
- C17 standard (ISO/IEC 9899:2018):
- 7.12.3.1 The fpclassify macro (p: TBD)
- 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)
[edit] See also
C++ documentation for fpclassify