std::fpclassify - cppreference.com (original) (raw)

Defined in header
(1)
int fpclassify( float num ); int fpclassify( double num ); int fpclassify( long double num ); (since C++11) (until C++23)
constexpr int fpclassify( /* floating-point-type */ num ); (since C++23)
Additional overloads
Defined in header
template< class Integer > int fpclassify( Integer num ); (A) (since C++11) (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.

[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

#include #include #include   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

isfinite(C++11) checks if the given number has finite value (function) [edit]
isinf(C++11) checks if the given number is infinite (function) [edit]
isnan(C++11) checks if the given number is NaN (function) [edit]
isnormal(C++11) checks if the given number is normal (function) [edit]
numeric_limits provides an interface to query properties of all fundamental numeric types (class template) [edit]
C documentation for fpclassify