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

CONFORMING TO

C99, 4.3BSD. 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 2.79 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)