Linux manual pages Section 3: Subroutines  

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] Note
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
copysign(), copysignf(), copysignl():
_SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
or cc -std=c99
[Note] 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.

For example, copysign(42.0, −1.0) and copysign(−42.0, −1.0) both return −42.0.

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.

SEE ALSO

signbit(3)

COLOPHON

This page is part of release 3.52 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)