std:: isunordered

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isunordered
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Defined in header <cmath>
(1)
bool isunordered ( float x, float y ) ;

bool isunordered ( double x, double y ) ;

bool isunordered ( long double x, long double y ) ;
(since C++11)
(until C++23)
constexpr bool isunordered ( /* floating-point-type */ x,
/* floating-point-type */ y ) ;
(since C++23)
Defined in header <cmath>
template < class Arithmetic1, class Arithmetic2 >
bool isunordered ( Arithmetic1 x, Arithmetic2 y ) ;
(A) (since C++11)
(constexpr since C++23)
1) Determines if the floating point numbers x and y are unordered, that is, one or both are NaN and thus cannot be meaningfully compared with each other. The library provides overloads for all cv-unqualified floating-point types as the type of the parameters x and y . (since C++23)
A) Additional overloads are provided for all other combinations of arithmetic types.

Parameters

x, y - floating-point or integer values

Return value

true if either x or y is NaN, false otherwise.

Notes

The additional overloads are not required to be provided exactly as (A) . They only need to be sufficient to ensure that for their first argument num1 and second argument num2 :

  • If num1 or num2 has type long double , then std :: isunordered ( num1, num2 ) has the same effect as std :: isunordered ( static_cast < long double > ( num1 ) ,
    static_cast < long double > ( num2 ) )     .
  • Otherwise, if num1 and/or num2 has type double or an integer type, then std :: isunordered ( num1, num2 ) has the same effect as std :: isunordered ( static_cast < double > ( num1 ) ,
    static_cast < double > ( num2 ) )     .
  • Otherwise, if num1 or num2 has type float , then std :: isunordered ( num1, num2 ) has the same effect as std :: isunordered ( static_cast < float > ( num1 ) ,
    static_cast < float > ( num2 ) )     .
(until C++23)

If num1 and num2 have arithmetic types, then std :: isunordered ( num1, num2 ) has the same effect as std :: isunordered ( static_cast < /* common-floating-point-type */ > ( num1 ) ,
static_cast < /* common-floating-point-type */ > ( num2 ) ) , where /* common-floating-point-type */ is the floating-point type with the greatest floating-point conversion rank and greatest floating-point conversion subrank between the types of num1 and num2 , arguments of integer type are considered to have the same floating-point conversion rank as double .

If no such floating-point type with the greatest rank and subrank exists, then overload resolution does not result in a usable candidate from the overloads provided.

(since C++23)

Example

Run this code 
#include <cmath>
#include <iostream>
 
#define SHOW_UNORDERED(x, y) \
    std::cout << std::boolalpha << "isunordered(" \
              << #x << ", " << #y << "): " \
              << std::isunordered(x, y) << '\n'
 
int main()
{
    SHOW_UNORDERED(10, 01);
    SHOW_UNORDERED(INFINITY, NAN);
    SHOW_UNORDERED(INFINITY, INFINITY);
    SHOW_UNORDERED(NAN, NAN);
}

Output: 

isunordered(10, 01): false
isunordered(INFINITY, NAN): true
isunordered(INFINITY, INFINITY): false
isunordered(NAN, NAN): true

See also

(C++11)
categorizes the given floating-point value
(function)
(C++11)
checks if the given number is NaN
(function)
C documentation for isunordered
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