copysign(3)

NAME
copysign, copysignf, copysignl - copy sign of a number

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);

    Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

copysign(), copysignf(), copysignl():
    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION
These 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.

ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
Interface | Attribute | Value
 | Thread safety | MT-Safe

VERSIONS
On architectures where the floating-point formats are not IEEE 754 compliant, these functions may treat a negative zero as positive.

STANDARDS
C11, POSIX.1-2008.

This function is defined in IEC 559 (and the appendix with recommended functions in IEEE 754/IEEE 854).

HISTORY
C99, POSIX.1-2001, 4.3BSD.

SEE ALSO
signbit(3)