osx man page for copysign

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

NAME
     copysign -- changes the sign of x to that of y

SYNOPSIS
     #include <math.h>

     double
     copysign(double x, double y);

     long double
     copysignl(long double x, long double y);

     float
     copysignf(float x, float y);

DESCRIPTION
     The copysign() functions return x with its sign changed to y's.

SPECIAL VALUES
     copysign(x, y) returns a NaN (with y's sign) if x is a NaN.

VECTOR OPERATIONS
     If you need to apply the copysign() functions to SIMD vectors or arrays, using the following functions provided by the Accelerate.framework
     may give significantly better performance:

     #include <Accelerate/Accelerate.h>

     vFloat vcopysignf(vFloat x, vFloat y);
     void vvcopysignf(float *z, const float *y, const float *x, const int *n);
     void vvcopysign(double *z, const double *y, const double *x, const int *n);

STANDARDS
     The copysign() functions conform to ISO/IEC 9899:2011.

BSD
								 December 11, 2006							       BSD