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, 0 shall be returned.

ERRORS

No errors are defined.

The following sections are informative.

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() , the Base Definitions volume of IEEE Std 1003.1-2001,
<math.h>

COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .