copysign(3)                Library Functions Manual                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   |
       +--------------------------------------------+---------------+---------+
       |copysign (), copysignf (), copysignl ()     | 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)

Linux man-pages 6.7               2023-10-31                       copysign(3)