isunordered

       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 ||
              _POSIX_C_SOURCE >= 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 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.

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
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                                  2010-09-20                      ISGREATER(3)
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