isless(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") 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
   integer 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 4.09 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/.

                              2016-03-15                      ISGREATER(3)

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