isunordered()

Determine whether two floating-point numbers are unordered

Synopsis:

#include <math.h>

#define isunordered( x, y ) ...

Arguments:

x, y
The floating-point values that you want to check.

Library:

libm
The general-purpose math library.
libm-sve
(QNX Neutrino 7.1 or later) A library that optimizes the code for ARMv8.2 chips that have Scalable Vector Extension hardware.

Your system requirements will determine how you should work with these libraries:

Note: Compile your program with the -fno-builtin option to prevent the compiler from using a built-in version of the function.

Description:

The isunordered() macro determines whether the given floating-point numbers are unordered (i.e., one or both are NaN and thus can't be meaningfully compared with each other).

Returns:

1 if the arguments are unordered, or 0 otherwise. If x or y is NaN, this function returns 1.

Classification:

C11, POSIX 1003.1

Safety:  
Cancellation point No
Interrupt handler Yes
Signal handler Yes
Thread Yes