The Open Group Base Specifications Issue 6

IEEE Std 1003.1, 2004 Edition

Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.A newer edition of this document exists here

#### 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 IEEE Std 1003.1-2001 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.

*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>*

#### 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.

*End of informative text.*

UNIX ® is a registered Trademark of The Open Group.

POSIX ® is a registered Trademark of The IEEE.

[ Main Index | XBD | XCU | XSH | XRAT
]