NAME

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

LIBRARY

       Math library (libm, -lm)

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);

   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 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(), isless(), islessequal(), islessgreater(),      │ Thread safety │ MT-Safe │
       │isunordered()                                                                 │               │         │
       └──────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

VERSIONS

       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.

STANDARDS

       C11, POSIX.1-2008.

HISTORY

       POSIX.1-2001, C99.

SEE ALSO

       fpclassify(3), isnan(3)