# copysign(3) [netbsd man page]

```COPYSIGN(3)						   BSD Library Functions Manual 					       COPYSIGN(3)

NAME
copysign, copysignf, copysignl -- functions to manipulate signs

LIBRARY
Math Library (libm, -lm)

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);

DESCRIPTION
The copysign(), copysignf(), and copysignl() functions return a value whose absolute value matches x, but whose sign bit is taken from y.

RETURN VALUES
Upon successful completion, all three functions return a value with the magnitude of x and the sign of y.	If x is NaN , the functions return
a NaN with the sign of y.

math(3), signbit(3)

STANDARDS
The described functions conform to ISO/IEC 9899:1999 (``ISO C99'').

CAVEATS
Note that on implementations that represent a signed zero but do not treat negative zero consistently in arithmetic operations, these func-
tions may regard the sign of zero as positive.

BSD								  April 13, 2011							       BSD```

## Check Out this Related Man Page

```COPYSIGN(3)						     Linux Programmer's Manual						       COPYSIGN(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);

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 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 posi-
tive.