saxpyx Subroutine

      subroutine saxpyx(a,x,y,n)
      implicit double precision (a-h,o-z)
      dimension x(*),y(*)
      if (a==0.D0) then
        do i=1,n
          x(i)=y(i)
        end do
      else
        do i=1,n
          x(i)=y(i)+a*x(i)
        end do
      end if
      end subroutine saxpyx