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std::fpclassify(3)	      C++ Standard Libary	    std::fpclassify(3)

NAME
       std::fpclassify - std::fpclassify

Synopsis
	  Defined in header <cmath>
	  int fpclassify( float	num );
								       (since
       C++11)
	  int  fpclassify( double num );				(until
       C++23)

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

	  1) Categorizes floating point	value num  into	 the  following	 cate-
       gories: zero,
	  subnormal,  normal,  infinite,  NAN, or implementation-defined cate-
       gory.
	  The library provides overloads of std::fpclassify for	all cv-unqual-
       ified
	  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.

Parameters
	  num -	floating-point or integer value

Return value
	  one of FP_INFINITE, FP_NAN, FP_NORMAL, FP_SUBNORMAL, FP_ZERO or
	  implementation-defined type, specifying the category of num.

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 inte-
       ger type,
	  std::fpclassify(num) has the same effect as
	  std::fpclassify(static_cast<double>(num)).

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

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

http://cppreference.com		  2024.06.10		    std::fpclassify(3)

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