NAME

isunordered - test if arguments are unordered

SYNOPSIS

#include <math.h>

int isunordered(real-floating x, real-floating y);


DESCRIPTION

^[CX] The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1-2008 defers to the ISO C standard.

The isunordered() macro shall determine whether its arguments are unordered.

RETURN VALUE

Upon successful completion, the isunordered() macro shall return 1 if its arguments are unordered, and 0 otherwise.

If x or y is NaN, 1 shall be returned.

ERRORS

No errors are defined.

EXAMPLES

None.

APPLICATION USAGE

The relational and equality operators support the usual mathematical relationships between numeric values. For any ordered pair of numeric values, exactly one of the relationships (less, greater, and equal) is true. Relational operators may raise the invalid floating-point exception when argument values are NaNs. For a NaN and a numeric value, or for two NaNs, just the unordered relationship is true. This macro is a quiet (non-floating-point exception raising) version of a relational operator. It facilitates writing efficient code that accounts for NaNs without suffering the invalid floating-point exception. In the SYNOPSIS section, real-floating indicates that the argument shall be an expression of real-floating type.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

isgreater, isgreaterequal, isless, islessequal, islessgreater

XBD <math.h>

CHANGE HISTORY

First released in Issue 6. Derived from the ISO/IEC 9899:1999 standard.

IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/50 is applied, correcting the RETURN VALUE section when x or y is NaN.