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

NAME
       std::fetestexcept - std::fetestexcept

Synopsis
	  Defined in header <cfenv>
	  int fetestexcept( int	excepts	);  (since C++11)

	  Determines  which  of	the specified subset of	the floating point ex-
       ceptions	are
	  currently set. The argument excepts is a bitwise OR of the  floating
       point exception
	  macros.

Parameters
	  excepts - bitmask listing the	exception flags	to test

Return value
	  Bitwise  OR of the floating-point exception macros that are both in-
       cluded in excepts
	  and correspond to floating-point exceptions currently	set.

Example
       // Run this code

	#include <iostream>
	#include <cfenv>
	#include <cmath>

	#pragma	STDC FENV_ACCESS ON

	volatile double	zero = 0.0; // volatile	not needed  where  FENV_ACCESS
       is supported
	volatile  double  one =	1.0;  // volatile not needed where FENV_ACCESS
       is supported

	int main()
	{
	    std::feclearexcept(FE_ALL_EXCEPT);
	    std::cout <<  "1.0/0.0 = " << 1.0 /	zero <<	'\n';
	    if(std::fetestexcept(FE_DIVBYZERO))	{
		std::cout << "division by zero reported\n";
	    } else {
		std::cout << "divsion by zero not reported\n";
	    }

	    std::feclearexcept(FE_ALL_EXCEPT);
	    std::cout << "1.0/10 = " <<	one/10 << '\n';
	    if(std::fetestexcept(FE_INEXACT)) {
		std::cout << "inexact result reported\n";
	    } else {
		std::cout << "inexact result not reported\n";
	    }

	    std::feclearexcept(FE_ALL_EXCEPT);
	    std::cout << "sqrt(-1) = " << std::sqrt(-1)	<< '\n';
	    if(std::fetestexcept(FE_INVALID)) {
		std::cout << "invalid result reported\n";
	    } else {
		std::cout << "invalid result not reported\n";
	    }
	}

Output:
	1.0/0.0	= inf
	division by zero reported
	1.0/10 = 0.1
	inexact	result reported
	sqrt(-1) = -nan
	invalid	result reported

See also
	  feclearexcept	clears the specified floating-point status flags
	  (C++11)	(function)

http://cppreference.com		  2022.07.31		  std::fetestexcept(3)

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