Returns x with the same sign as y.

    This function is supported on OpenVMS Integrity servers and
    Alpha only.

    Format

      #include  <math.h>

      double copysign  (double x, double y);

      float copysignf  (float x, float y);

                       (Integrity servers, Alpha)

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

                             (Integrity servers, Alpha)