set_length_star Subroutine

    subroutine set_length_star(this, length_x, length_y, length_z)
        class(star) :: this
        integer, intent(in) :: length_x, length_y
        integer, intent(in), optional :: length_z
        character(*), parameter :: this_routine = "set_length_star"

        ! actually the length of a start is not really defined..
        ! maybe i should rethink if i make this part of the
        ! original lattice class then..
        call stop_all(this_routine, "length not defined for 'star' geometry!")

        unused_var(length_x)
        unused_var(length_y)
        if (present(length_z)) then
            unused_var(length_z)
        end if
        unused_var(this)
    end subroutine set_length_star