isless

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:
              _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L

DESCRIPTION
       The normal relational operations (like <, "less than") fail if  one  of
       the operands is NaN.  This will cause an exception.  To avoid this, C99
       defines the macros listed below.

       These macros are guaranteed to evaluate their arguments only once.  The
       arguments  must be of real floating-point type (note: do not pass inte-
       ger values as arguments to these macros, since the arguments  will  not
       be promoted to real-floating types).

       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.

ATTRIBUTES
       For   an   explanation   of   the  terms  used  in  this  section,  see
       attributes(7).

       +-------------------------------+---------------+---------+
       |Interface                      | Attribute     | Value   |
       +-------------------------------+---------------+---------+
       |isgreater(), isgreaterequal(), | Thread safety | MT-Safe |
       |isless(), islessequal(),       |               |         |
       |islessgreater(), isunordered() |               |         |
       +-------------------------------+---------------+---------+
CONFORMING TO
       POSIX.1-2001, POSIX.1-2008, C99.

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 4.15 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest     version     of     this    page,    can    be    found    at
       https://www.kernel.org/doc/man-pages/.

                                  2017-09-15                      ISGREATER(3)
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