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 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).
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
COLOPHON
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