COPYSIGN

Section: Linux Programmer's Manual (3)
Updated: 2008-08-05
Index Return to Main Contents

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);

Link with -lm.

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

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 3.22 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/.