Isunordered
Defined in header <cmath>
.
Description
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
(od C++23).
Additional Overloads are provided for all other combinations of arithmetic types.
Declarations
- C++23
- C++11
// 1)
constexpr bool isunordered( /* floating-point-type */ x,
/* floating-point-type */ y );
// 2)
template< class Arithmetic1, class Arithmetic2 >
constexpr bool isunordered( Arithmetic1 x, Arithmetic2 y );
// 1)
bool isunordered( float x, float y );
// 2)
bool isunordered( double x, double y );
// 3)
bool isunordered( long double x, long double y );
// 4)
template< class Arithmetic1, class Arithmetic2 >
bool isunordered( Arithmetic1 x, Arithmetic2 y );
Parameters
x
, y
- floating-point or integer values
Return value
true
if either x
or y
is NaN
, false
otherwise.
Notes
The built-in operator >
and operator <
for floating-point numbers may raise FE_INVALID
if one or both of the arguments is NaN
.
This function is a "quiet" version of the expression x < y || x > y
.
The additional overloads are not required to be provided exactly as Additional Overloads.
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))
. (do 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.
Examples
#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);
}
isunordered(10, 01): false
isunordered(INFINITY, NAN): true
isunordered(INFINITY, INFINITY): false
isunordered(NAN, NAN): true