mirror of https://github.com/mkerrisk/man-pages
92 lines
2.5 KiB
Groff
92 lines
2.5 KiB
Groff
.\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de)
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.\" Distributed under GPL
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.\" 2002-07-27 Walter Harms
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.\" this was done with the help of the glibc manual
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.\"
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.TH ISGREATER 3 2008-08-05 "" "Linux Programmer's Manual"
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.SH NAME
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isgreater, isgreaterequal, isless, islessequal, islessgreater,
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isunordered \- floating-point relational tests without exception for NaN
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.SH SYNOPSIS
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.nf
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.B #include <math.h>
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.sp
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.BI "int isgreater(" x ", " y );
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.sp
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.BI "int isgreaterequal(" x ", " y );
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.sp
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.BI "int isless(" x ", " y );
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.sp
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.BI "int islessequal(" x ", " y );
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.sp
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.BI "int islessgreater(" x ", " y );
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.sp
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.BI "int isunordered(" x ", " y );
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.fi
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.sp
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Link with \fI\-lm\fP.
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.sp
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.in -4n
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.in
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.sp
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.ad l
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All functions described here:
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_XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE; or
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.I cc\ -std=c99
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.ad b
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.SH DESCRIPTION
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The normal relation operations (like \fB<\fP, "less than")
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will fail if one of the operands is NaN.
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This will cause an exception.
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To avoid this, C99 defines these macros.
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The macros are guaranteed to evaluate their operands only once.
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The operands can be of any real floating-point type.
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.TP
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.BR isgreater ()
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determines \fI(x)\ >\ (y)\fP without an exception
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if \fIx\fP or \fIy\fP is NaN.
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.TP
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.BR isgreaterequal ()
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determines \fI(x)\ >=\ (y)\fP without an exception
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if \fIx\fP or \fIy\fP is NaN.
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.TP
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.BR isless ()
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determines \fI(x)\ <\ (y)\fP without an exception
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if \fIx\fP or \fIy\fP is NaN.
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.TP
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.BR islessequal ()
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determines \fI(x)\ <=\ (y)\fP without an exception
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if \fIx\fP or \fIy\fP is NaN.
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.TP
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.BR islessgreater ()
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determines \fI(x)\ < (y) || (x) >\ (y)\fP
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without an exception if \fIx\fP or \fIy\fP is NaN.
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This macro is not equivalent to \fIx\ !=\ y\fP because that expression is
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true if \fIx\fP or \fIy\fP is NaN.
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.TP
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.BR isunordered ()
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determines whether its arguments are unordered, that is, whether
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at least one of the arguments is a NaN.
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.SH RETURN VALUE
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The macros other than
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.BR isunordered ()
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return the result of the relational comparison;
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these macros return 0 if either argument is a NaN.
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.BR isunordered ()
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returns 1 if \fIx\fP or \fIy\fP is NaN and 0 otherwise.
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.SH ERRORS
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No errors occur.
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.SH "CONFORMING TO"
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C99, POSIX.1-2001.
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.SH NOTES
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Not all hardware supports these functions,
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and where hardware support isn't provided, they will be emulated by macros.
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This will result in a performance penalty.
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Don't use these functions if NaN is of no concern for you.
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.SH "SEE ALSO"
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.BR fpclassify (3),
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.BR isnan (3)
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