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 

       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 featuretestmacros(7)):

       All functions described here:
              XOPENSOURCE >= 600 || ISOC99SOURCE ||
              POSIXCSOURCE >= 200112L;
              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 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
       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 3.53 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/.



                                  2012-05-06                      ISGREATER(3)