fpclassify
From cppreference.com
Common mathematical functions
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Defined in header <math.h>
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#define fpclassify(arg) /* implementation defined */ |
(since C99) | |
Categorizes floating-point value arg
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 <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
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)
See also
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(C99)
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checks if the given number has finite value (function macro) |
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(C99)
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checks if the given number is infinite (function macro) |
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(C99)
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checks if the given number is NaN (function macro) |
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(C99)
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checks if the given number is normal (function macro) |
C++ documentation for fpclassify
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