linux man page for copysign

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);

       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.

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.

SEE ALSO
       signbit(3)

COLOPHON
       This page is part of release 3.27 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
								    2010-09-20							       COPYSIGN(3)