Defined in header <cmath>
bool isunordered( float x, float y );
(1) (since C++11)
bool isunordered( double x, double y );
(2) (since C++11)
bool isunordered( long double x, long double y );
(3) (since C++11)
bool isunordered( Arithmetic x, Arithmetic y );
(4) (since C++11)
1-3) 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.
4) A set of overloads or a function template for all combinations of arguments of arithmetic type not covered by (1-3). If any argument has integral type, it is cast to double.


x - floating point value
y - floating point value

Return value

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

See also

categorizes the given floating point value
checks if the given number is NaN

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