set_length_cube Subroutine

    subroutine set_length_cube(this, length_x, length_y, length_z)
        class(cube) :: this
        integer, intent(in) :: length_x, length_y
        integer, intent(in), optional :: length_z
#ifdef DEBUG_
        character(*), parameter :: this_routine = "set_length_cube"
#endif

        ASSERT(present(length_z))
        ASSERT(length_x > 1)
        ASSERT(length_y > 1)
        ASSERT(length_z > 1)

        this%length(1) = length_x
        this%length(2) = length_y
        this%length(3) = length_z

    end subroutine set_length_cube