indexing
	description: "[
		Hierarchical structures in which each item has zero or
		one immediate predecessor, and zero or more successors.
	]"
	status: "See notice at end of class"
	names: hierarchical, traversing
	access: cursor
	contents: generic
	date: "$Date$"
	revision: "$Revision$"

deferred class interface
	HIERARCHICAL [G]

feature -- Access

	has (v: G): BOOLEAN
			-- Does structure include v?
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from CONTAINER)
		ensure -- from CONTAINER
			not_found_in_empty: Result implies not is_empty

	item: G
			-- Item at current position
			-- (from TRAVERSABLE)
		require -- from TRAVERSABLE
			not_off: not off

	successor_count: INTEGER
			-- Number of successors of current element
		require
			not_off: not off

feature -- Status report

	changeable_comparison_criterion: BOOLEAN
			-- May object_comparison be changed?
			-- (Answer: yes by default.)
			-- (from CONTAINER)

	is_empty: BOOLEAN
			-- Is there no element?
			-- (from CONTAINER)

	object_comparison: BOOLEAN
			-- Must search operations use equal rather than =
			-- for comparing references? (Default: no, use =.)
			-- (from CONTAINER)

	off: BOOLEAN
			-- Is there no current item?
			-- (from TRAVERSABLE)

feature -- Status setting

	compare_objects
			-- Ensure that future search operations will use equal
			-- rather than = for comparing references.
			-- (from CONTAINER)
		require -- from CONTAINER
			changeable_comparison_criterion
		ensure -- from CONTAINER
			object_comparison

	compare_references
			-- Ensure that future search operations will use =
			-- rather than equal for comparing references.
			-- (from CONTAINER)
		require -- from CONTAINER
			changeable_comparison_criterion
		ensure -- from CONTAINER
			reference_comparison: not object_comparison

feature -- Cursor movement

	down (i: INTEGER)
			-- Move to i-th successor.
		require
			not_off: not off
			argument_within_bounds: i >= 1 and i <= successor_count

	start
			-- Move to first position if any.
			-- (from TRAVERSABLE)

	up
			-- Move to predecessor.
		require
			not_off: not off

feature -- Conversion

	linear_representation: LINEAR [G]
			-- Representation as a linear structure
			-- (from CONTAINER)

feature -- Iteration

	do_all (action: PROCEDURE [ANY, TUPLE [G]])
			-- Apply action to every item.
			-- Semantics not guaranteed if action changes the structure;
			-- in such a case, apply iterator to clone of structure instead.
			-- (from TRAVERSABLE)
		require -- from TRAVERSABLE
			action_exists: action /= void

	do_if (action: PROCEDURE [ANY, TUPLE [G]]; test: FUNCTION [ANY, TUPLE [G], BOOLEAN])
			-- Apply action to every item that satisfies test.
			-- Semantics not guaranteed if action or test changes the structure;
			-- in such a case, apply iterator to clone of structure instead.
			-- (from TRAVERSABLE)
		require -- from TRAVERSABLE
			action_exists: action /= void
			test_exits: test /= void

	for_all (test: FUNCTION [ANY, TUPLE [G], BOOLEAN]): BOOLEAN
			-- Is test true for all items?
			-- (from TRAVERSABLE)
		require -- from TRAVERSABLE
			test_exits: test /= void

	there_exists (test: FUNCTION [ANY, TUPLE [G], BOOLEAN]): BOOLEAN
			-- Is test true for at least one item?
			-- (from TRAVERSABLE)
		require -- from TRAVERSABLE
			test_exits: test /= void

invariant

	non_negative_successor_count: successor_count >= 0
		-- from ANY
	reflexive_equality: standard_is_equal (Current)
	reflexive_conformance: conforms_to (Current)
		-- from TRAVERSABLE
	empty_constraint: is_empty implies off

indexing
	library: "[
			EiffelBase: Library of reusable components for Eiffel.
	]"
	status: "[
			Copyright 1986-2001 Interactive Software Engineering (ISE).
			For ISE customers the original versions are an ISE product
			covered by the ISE Eiffel license and support agreements.
	]"
	license: "[
			EiffelBase may now be used by anyone as FREE SOFTWARE to
			develop any product, public-domain or commercial, without
			payment to ISE, under the terms of the ISE Free Eiffel Library
			License (IFELL) at http://eiffel.com/products/base/license.html.
	]"
	source: "[
			Interactive Software Engineering Inc.
			ISE Building
			360 Storke Road, Goleta, CA 93117 USA
			Telephone 805-685-1006, Fax 805-685-6869
			Electronic mail <info@eiffel.com>
			Customer support http://support.eiffel.com
	]"
	info: "[
			For latest info see award-winning pages: http://eiffel.com
	]"

end -- class HIERARCHICAL