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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 3.21 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)