suse man page for isunordered

ISGREATER(3)						     Linux Programmer's Manual						      ISGREATER(3)

NAME
       isgreater, isgreaterequal, isless, islessequal, islessgreater, isunordered - floating-point relational tests without exception for NaN

SYNOPSIS
       #include <math.h>

       int isgreater(x, y);

       int isgreaterequal(x, y);

       int isless(x, y);

       int islessequal(x, y);

       int islessgreater(x, y);

       int isunordered(x, y);

       Link with -lm.

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       All functions described here: _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or cc -std=c99

DESCRIPTION
       The  normal  relation  operations  (like  <, "less than") will fail if one of the operands is NaN.  This will cause an exception.  To avoid
       this, C99 defines these macros.	The macros are guaranteed to evaluate their operands only once.  The operands can be of any real floating-
       point type.

       isgreater()
	      determines (x) > (y) without an exception if x or y is NaN.

       isgreaterequal()
	      determines (x) >= (y) without an exception if x or y is NaN.

       isless()
	      determines (x) < (y) without an exception if x or y is NaN.

       islessequal()
	      determines (x) <= (y) without an exception if x or y is NaN.

       islessgreater()
	      determines  (x) <  (y)  ||  (x)  > (y)  without  an exception if x or y is NaN.  This macro is not equivalent to x != y because that
	      expression is true if x or y is NaN.

       isunordered()
	      determines whether its arguments are unordered, that is, whether at least one of the arguments is a NaN.

RETURN VALUE
       The macros other than isunordered() return the result of the relational comparison; these macros return 0 if either argument is a NaN.

       isunordered() returns 1 if x or y is NaN and 0 otherwise.

ERRORS
       No errors occur.

CONFORMING TO
       C99, POSIX.1-2001.

NOTES
       Not all hardware supports these functions, and where hardware support isn't provided, they will be emulated by macros.  This will result in
       a performance penalty.  Don't use these functions if NaN is of no concern for you.

SEE ALSO
       fpclassify(3), isnan(3)

COLOPHON
       This  page is part of release 3.25 of the Linux man-pages project.  A description of the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.

								    2008-08-05							      ISGREATER(3)