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[thirdparty/man-pages.git] / man3 / copysign.3

.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\"
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.\" References consulted:
.\"     Linux libc source code
.\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
.\"     386BSD man pages
.\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
.\" Modified 2002-08-10 by Walter Harms (walter.harms@informatik.uni-oldenburg.de)
.TH COPYSIGN 3  2015-03-02 "GNU" "Linux Programmer's Manual"
.SH NAME
copysign, copysignf, copysignl \- copy sign of a number
.SH SYNOPSIS
.nf
.B #include <math.h>
.sp
.BI "double copysign(double " x ", double " y );
.br
.BI "float copysignf(float " x ", float " y );
.br
.BI "long double copysignl(long double " x ", long double " 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
.BR copysign (),
.BR copysignf (),
.BR copysignl ():
.RS 4
_SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE ||
_POSIX_C_SOURCE\ >=\ 200112L;
.br
or
.I cc\ -std=c99
.RE
.ad b
.SH DESCRIPTION
These functions return a value whose absolute value matches that of
.IR x ,
but whose sign bit matches that of
.IR y .

For example,
.I "copysign(42.0,\ \-1.0)"
and
.I "copysign(\-42.0, \-1.0)"
both return \-42.0.
.SH RETURN VALUE
On success, these functions return a value whose magnitude is taken from
.I x