.\" $NetBSD: copysign.3,v 1.4 2017/09/28 15:03:18 maya Exp $
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.\" Copyright (c) 2011 Jukka Ruohonen <jruohonen@iki.fi>
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.Dd September 28, 2017
.Dt COPYSIGN 3
.Os
.Sh NAME
.Nm copysign ,
.Nm copysignf ,
.Nm copysignl
.Nd functions to manipulate signs
.Sh LIBRARY
.Lb libm
.Sh SYNOPSIS
.In math.h
.Ft double
.Fn copysign "double x" "double y"
.Ft float
.Fn copysignf "float x" "float y"
.Ft long double
.Fn copysignl "long double x" "long double y"
.In tgmath.h
.Ft real-floating
.Fn copysign "real-floating x" "real-floating y"
.Sh DESCRIPTION
The
.Fn copysign ,
.Fn copysignf ,
and
.Fn copysignl
functions return a value whose absolute value matches
.Fa x ,
but whose sign bit is taken from
.Fa y .
.Sh RETURN VALUES
Upon successful completion,
all three functions return a value with the magnitude of
.Fa x
and the sign of
.Fa y .
If
.Fa x
is
\*(Na ,
the functions return a
\*(Na
with the sign of
.Fa y .
.Sh SEE ALSO
.Xr math 3 ,
.Xr signbit 3
.Sh STANDARDS
The described functions conform to
.St -isoC-99 .
.\"
.\" XXX: Verify this.
.\"
.\" The functions are also recommended by
.\" .St -ieee754
.\"
.\" .Sh HISTORY
.\"
.\" XXX: Fill this.
.\"
.\" These functions first appeared in ???.
.\"
.Sh CAVEATS
Note that on implementations that represent a signed zero
but do not treat negative zero consistently in arithmetic operations,
these functions may regard the sign of zero as positive.