**copysign**

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 || _POSIX_C_SOURCE >= 200112L;
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.
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 appen-
dix with recommended functions in IEEE 754/IEEE 854).
NOTES
On architectures where the floating-point formats are not IEEE 754 com-
pliant, the copysign() functions may treat a negative zero as positive.
SEE ALSO
**signbit(3)**
COLOPHON
This page is part of release 3.54 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/.
GNU 2012-03-25 **COPYSIGN(3)**

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