std::fpclassify
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Defined in header
<cmath>
(1)
int fpclassify( float num );
(since C++11) int fpclassify( double num );
(until C++23)
constexpr int fpclassify( /* floating-point-type */ num );
(since C++23)
Defined in header
<cmath>
template< class Integer >
int fpclassify( Integer num );
(A)
(since C++11) int fpclassify( Integer num );
(constexpr since C++23)
1) Categorizes floating point value num into the following categories: zero, subnormal, normal, infinite, NAN, or implementation-defined category. The library provides overloads of
std::fpclassify for all cv-unqualified floating-point types as the type of the parameter num.(since C++23)A) Additional overloads are provided for all integer types, which are treated as double.
Contents
[edit] Parameters
num
-
floating-point or integer value
[edit] Return value
one of FP_INFINITE , FP_NAN , FP_NORMAL , FP_SUBNORMAL , FP_ZERO or implementation-defined type, specifying the category of num.
[edit] Notes
The additional overloads are not required to be provided exactly as (A). They only need to be sufficient to ensure that for their argument num of integer type, std::fpclassify(num) has the same effect as std::fpclassify(static_cast<double>(num)).
[edit] Example
Run this code
#include <cfloat> #include <cmath> #include <iostream> auto show_classification(double x) { switch (std::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() { std::cout << "1.0/0.0 is " << show_classification(1 / 0.0) << '\n' << "0.0/0.0 is " << show_classification(0.0 / 0.0) << '\n' << "DBL_MIN/2 is " << show_classification(DBL_MIN / 2) << '\n' << "-0.0 is " << show_classification(-0.0) << '\n' << "1.0 is " << show_classification(1.0) << '\n'; }
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] See also
C documentation for fpclassify