.\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de)
.\" Distributed under GPL
.\" 2002-07-27 Walter Harms
.\" this was done with the help of the glibc manual
.\"
.TH ISGREATER 3  2008-08-05 "" "Linux Programmer's Manual"
.SH NAME
isgreater, isgreaterequal, isless, islessequal, islessgreater,
isunordered \- floating-point relational tests without exception for NaN
.SH SYNOPSIS
.nf
.B #include <math.h>
.sp
.BI "int isgreater(" x ", " y );
.sp
.BI "int isgreaterequal(" x ", " y );
.sp
.BI "int isless(" x ", " y );
.sp
.BI "int islessequal(" x ", " y );
.sp
.BI "int islessgreater(" x ", " y );
.sp
.BI "int isunordered(" x ", " y );
.fi
.sp
Link with \fI\-lm\fP.
.sp
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.sp
.ad l
All functions described here:
_XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE; or
.I cc\ -std=c99
.ad b
.SH DESCRIPTION
The normal relation operations (like \fB<\fP, "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.
.TP
.BR isgreater ()
determines \fI(x)\ >\ (y)\fP without an exception
if \fIx\fP or \fIy\fP is NaN.
.TP
.BR isgreaterequal ()
determines \fI(x)\ >=\ (y)\fP without an exception
if \fIx\fP or \fIy\fP is NaN.
.TP
.BR isless ()
determines \fI(x)\ <\ (y)\fP without an exception
if \fIx\fP or \fIy\fP is NaN.
.TP
.BR islessequal ()
determines \fI(x)\ <=\ (y)\fP without an exception
if \fIx\fP or \fIy\fP is NaN.
.TP
.BR islessgreater ()
determines \fI(x)\ < (y) || (x) >\ (y)\fP
without an exception if \fIx\fP or \fIy\fP is NaN.
This macro is not equivalent to \fIx\ !=\ y\fP because that expression is
true if \fIx\fP or \fIy\fP is NaN.
.TP
.BR isunordered ()
determines whether its arguments are unordered, that is, whether
at least one of the arguments is a NaN.
.SH RETURN VALUE
The macros other than
.BR isunordered ()
return the result of the relational comparison;
these macros return 0 if either argument is a NaN.

.BR isunordered ()
returns 1 if \fIx\fP or \fIy\fP is NaN and 0 otherwise.
.SH ERRORS
No errors occur.
.SH "CONFORMING TO"
C99, POSIX.1-2001.
.SH 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.
.SH "SEE ALSO"
.BR fpclassify (3),
.BR isnan (3)