int isunordered(real-floating x, real-floating y);
The isunordered() macro shall determine whether its arguments are unordered.
Upon successful completion, the isunordered() macro shall return 1 if its arguments are unordered, and 0 otherwise.
If x or y is NaN, 0 shall be returned.
No errors are defined.
The following sections are informative.
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.
isgreater() , isgreaterequal() , isless() , islessequal() , islessgreater() , the Base Definitions volume of IEEE Std 1003.1-2001, <math.h>