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copysign

Section: C Library Functions (3)
Updated: 202-0-08
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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
copysign(), copysignf(), copysignl()	Thread safety	M-Safe

VERSIONS

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

STANDARDS

C11, POSIX.-2008. This function is defined in IEC 559 (and the appendix with recommended functions in IEEE 754/IEEE 854).

HISTORY

C99, POSIX.-2001, 4.3BSD.