copysign(3) — Linux manual pages

Linux manual pages	Section 3

Name

copysign, copysignf, copysignl — copy sign of a number

Synopsis

#include <math.h>

`double copysign(`	double `x`,
	double `y)`;

`float copysignf(`	float `x`,
	float `y)`;

`long double copysignl(`	long double `x`,
	long double `y)`;

Note

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
`copysign`(), `copysignf`(), `copysignl`():
`_SVID_SOURCE` \|\| `_BSD_SOURCE` \|\| `_XOPEN_SOURCE` >= 600 \|\| `_ISOC99_SOURCE`;
or cc `-std=c99`

	Note
	Link with `−lm`.

DESCRIPTION

The copysign() functions return a value whose absolute value matches that of x, but whose sign bit matches that of y.

RETURN VALUE

On success, these functions return a value whose magnitude is taken from x and whose sign is taken from y.

If x is a NaN, a NaN with the sign bit of y is returned.

ERRORS

No errors occur.

CONFORMING TO

C99, POSIX.1-2001. This function is defined in IEC 559 (and the appendix with recommended functions in IEEE 754/IEEE 854).

NOTES

On architectures where the floating-point formats are not IEEE 754 compliant, the copysign() functions may treat a negative zero as positive.

COLOPHON

This page is part of release 3.24 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.

  Copyright 1993 David Metcalfe (davidprism.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 (faithcs.unc.edu)
Modified 2002-08-10 by Walter Harms (walter.harmsinformatik.uni-oldenburg.de)