.\" 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  2007-03-31 "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 \-lm.
.SH DESCRIPTION
The \fBcopysign\fP() functions return a value whose absolute value matches
that of \fIx\fP, but whose sign matches that of \fIy\fP.
If \fIx\fP is a NaN, then a NaN with the sign of \fIy\fP is returned.
.SH NOTES
On architectures where the floating-point formats are not IEEE 754 compliant,
the \fBcopysign\fP() functions may treat a negative zero as positive.
.SH "CONFORMING TO"
C99, 4.3BSD.
This function is defined in IEC 559 (and the appendix with
recommended functions in IEEE 754/IEEE 854).
.SH "SEE ALSO"
.BR signbit (3)