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 <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 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 ex-
pression 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 at-
tributes(7).
+-------------------------------+---------------+---------+
|Interface | Attribute | Value |
+-------------------------------+---------------+---------+
|isgreater(), isgreaterequal(), | Thread safety | MT-Safe |
|isless(), islessequal(), is- | | |
|lessgreater(), 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 5.07 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/.
2017-09-15 ISGREATER(3)