uniform_gradient_assign Subroutine

  impure elemental subroutine uniform_gradient_assign(this,rhs)
    !* Author: Chris MacMackin
    !  Date: July 2017
    !
    ! \({\rm field} = {\rm field}\)
    !
    class(uniform_gradient_field), intent(inout) :: this
    class(scalar_field), intent(in) :: rhs
    call rhs%guard_temp()
    select type(rhs)
    class is(uniform_gradient_field)
      this%uniform_scalar_field = rhs%uniform_scalar_field
      if (allocated(rhs%grad)) then
        this%grad = rhs%grad
      else if (allocated(this%grad)) then
        deallocate(this%grad)
      end if
      call this%unset_temp()
    class is(uniform_scalar_field)
      this%uniform_scalar_field = rhs
      if (allocated(this%grad)) deallocate(this%grad)
      call this%unset_temp()
    class default
      error stop ('Assigning incompatible type to uniform_gradient_field')
    end select
    call rhs%clean_temp()
  end subroutine uniform_gradient_assign