indexing
	description: "Base class for EV_TREE and EV_TREE_ITEM."
	legal: "See notice at end of class."
	status: "See notice at end of class."
	date: "$Date: 2006-01-22 18:25:44 -0800 (Sun, 22 Jan 2006) $"
	revision: "$Revision: 56675 $"

deferred class interface
	EV_TREE_NODE_LIST

feature -- Access

	cursor: EV_DYNAMIC_LIST_CURSOR [EV_TREE_NODE]
			-- Current cursor position.
			-- (from EV_DYNAMIC_LIST)
		require -- from  CURSOR_STRUCTURE
			True
		ensure -- from CURSOR_STRUCTURE
			cursor_not_void: Result /= Void
		ensure then -- from EV_DYNAMIC_LIST
			bridge_ok: Result.is_equal (implementation.cursor)

	data: ANY
			-- Arbitrary user data may be stored here.
			-- (from EV_ANY)

	first: like item
			-- Item at first position
			-- (from CHAIN)
		require -- from CHAIN
			not_empty: not is_empty

	generating_type: STRING_8
			-- Name of current object's generating type
			-- (type of which it is a direct instance)
			-- (from ANY)

	generator: STRING_8
			-- Name of current object's generating class
			-- (base class of the type of which it is a direct instance)
			-- (from ANY)

	has (v: like item): BOOLEAN
			-- Does chain include `v'?
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from CHAIN)
		require -- from  CONTAINER
			True
		ensure -- from CONTAINER
			not_found_in_empty: Result implies not is_empty

	has_recursively (an_item: EV_TREE_NODE): BOOLEAN
			-- Is `an_item' contained in `Current' at any level?
		require
			item_not_void: an_item /= Void
		ensure
			not_found_in_empty: Result implies not is_empty
			index_not_changed: old index = index

	i_th alias "[]" (i: INTEGER_32): like item
			-- Item at `i'-th position.
			-- (from EV_DYNAMIC_LIST)
		require -- from TABLE
			valid_key: valid_index (i)
		ensure then -- from EV_DYNAMIC_LIST
			bridge_ok: Result.is_equal (implementation.i_th (i))

	index: INTEGER_32
			-- Current position.
			-- (from EV_DYNAMIC_LIST)
		require -- from  LINEAR
			True
		ensure then -- from EV_DYNAMIC_LIST
			bridge_ok: Result = implementation.index

	index_of (v: like item; i: INTEGER_32): INTEGER_32
			-- Index of `i'th occurrence of `v'.
			-- (from EV_DYNAMIC_LIST)
		require -- from LINEAR
			positive_occurrences: i > 0
		ensure -- from LINEAR
			non_negative_result: Result >= 0
		ensure then -- from EV_DYNAMIC_LIST
			bridge_ok: Result = implementation.index_of (v, i)

	item: EV_TREE_NODE
			-- Item at current position.
			-- (from EV_DYNAMIC_LIST)
		require -- from TRAVERSABLE
			not_off: not off
		require -- from ACTIVE
			readable: readable
		ensure then -- from EV_DYNAMIC_LIST
			not_void: Result /= Void
			bridge_ok: Result.is_equal (implementation.item)

	last: like item
			-- Item at last position
			-- (from CHAIN)
		require -- from CHAIN
			not_empty: not is_empty

	sequential_occurrences (v: like item): INTEGER_32
			-- Number of times `v' appears.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from LINEAR)
		require -- from  BAG
			True
		ensure -- from BAG
			non_negative_occurrences: Result >= 0

	retrieve_item_by_data (some_data: ANY; should_compare_objects: BOOLEAN): EV_TREE_NODE
			-- `Result' is first item in `Current' with data
			-- matching `some_data'. Compare objects if
			-- `should_compare_objects' otherwise compare references.
			-- (from EV_DYNAMIC_LIST)
		ensure -- from EV_DYNAMIC_LIST
			not_found_in_empty: Result /= Void implies not is_empty
			index_not_changed: old index = index

	retrieve_item_recursively_by_data (some_data: ANY; should_compare_objects: BOOLEAN): EV_TREE_NODE
			-- If data contained in a tree item at any level then
			-- assign this item to `Result'. Compare objects if
			-- `should_compare_objects' otherwise compare references.
		ensure
			not_found_in_empty: Result /= Void implies not is_empty
			index_not_changed: old index = index

	retrieve_items_by_data (some_data: ANY; should_compare_objects: BOOLEAN): ARRAYED_LIST [EV_TREE_NODE]
			-- `Result' is all items in `Current' with data
			-- matching `some_data'. Compare objects if
			-- `should_compare_objects' otherwise compare references.
			-- (from EV_DYNAMIC_LIST)
		ensure -- from EV_DYNAMIC_LIST
			result_not_void: Result /= Void
			not_found_in_empty: not Result.is_empty implies not is_empty
			index_not_changed: old index = index

	retrieve_items_recursively_by_data (some_data: ANY; should_compare_objects: BOOLEAN): ARRAYED_LIST [EV_TREE_NODE]
			-- `Result' is all tree items contained in `Current' at any level
			-- with data matching `some_data'. Compare objects if
			-- `should_compare_objects' otherwise compare references.
		ensure
			result_not_void: Result /= Void
			not_found_in_empty: not Result.is_empty implies not is_empty
			index_not_changed: old index = index

	infix "@" (i: INTEGER_32): like item assign put_i_th
			-- Item at `i'-th position
			-- Was declared in CHAIN as synonym of i_th.
			-- (from CHAIN)
		require -- from TABLE
			valid_key: valid_index (i)
	
feature -- Measurement

	count: INTEGER_32
			-- Number of items.
			-- (from EV_DYNAMIC_LIST)
		require -- from  FINITE
			True
		require -- from  SET
			True
		ensure then -- from EV_DYNAMIC_LIST
			bridge_ok: Result = implementation.count

	index_set: INTEGER_INTERVAL
			-- Range of acceptable indexes
			-- (from CHAIN)
		require -- from  INDEXABLE
			True
		ensure -- from INDEXABLE
			not_void: Result /= Void
		ensure then -- from CHAIN
			count_definition: Result.count = count

	occurrences (v: like item): INTEGER_32
			-- Number of times `v' appears.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from CHAIN)
		require -- from  BAG
			True
		require -- from  LINEAR
			True
		ensure -- from BAG
			non_negative_occurrences: Result >= 0
	
feature -- Comparison

	frozen deep_equal (some: ANY; other: like arg #1): BOOLEAN
			-- Are `some' and `other' either both void
			-- or attached to isomorphic object structures?
			-- (from ANY)
		ensure -- from ANY
			shallow_implies_deep: standard_equal (some, other) implies Result
			both_or_none_void: (some = Void) implies (Result = (other = Void))
			same_type: (Result and (some /= Void)) implies some.same_type (other)
			symmetric: Result implies deep_equal (other, some)

	frozen equal (some: ANY; other: like arg #1): BOOLEAN
			-- Are `some' and `other' either both void or attached
			-- to objects considered equal?
			-- (from ANY)
		ensure -- from ANY
			definition: Result = (some = Void and other = Void) or else ((some /= Void and other /= Void) and then some.is_equal (other))

	is_equal (other: like Current): BOOLEAN
			-- Does `other' contain the same elements?
			-- (from LIST)
		require -- from ANY
			other_not_void: other /= Void
		ensure -- from ANY
			symmetric: Result implies other.is_equal (Current)
			consistent: standard_is_equal (other) implies Result
		ensure then -- from LIST
			indices_unchanged: index = old index and other.index = old other.index
			true_implies_same_size: Result implies count = other.count

	frozen standard_equal (some: ANY; other: like arg #1): BOOLEAN
			-- Are `some' and `other' either both void or attached to
			-- field-by-field identical objects of the same type?
			-- Always uses default object comparison criterion.
			-- (from ANY)
		ensure -- from ANY
			definition: Result = (some = Void and other = Void) or else ((some /= Void and other /= Void) and then some.standard_is_equal (other))

	frozen standard_is_equal (other: like Current): BOOLEAN
			-- Is `other' attached to an object of the same type
			-- as current object, and field-by-field identical to it?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		ensure -- from ANY
			same_type: Result implies same_type (other)
			symmetric: Result implies other.standard_is_equal (Current)
	
feature -- Status report

	after: BOOLEAN
			-- Is there no valid cursor position to the right of cursor?
			-- (from LIST)
		require -- from  LINEAR
			True

	before: BOOLEAN
			-- Is there no valid cursor position to the left of cursor?
			-- (from LIST)
		require -- from  BILINEAR
			True

	conforms_to (other: ANY): BOOLEAN
			-- Does type of current object conform to type
			-- of `other' (as per Eiffel: The Language, chapter 13)?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void

	exhausted: BOOLEAN
			-- Has structure been completely explored?
			-- (from LINEAR)
		ensure -- from LINEAR
			exhausted_when_off: off implies Result

	extendible: BOOLEAN is True
			-- May new items be added? (Answer: yes.)
			-- (from DYNAMIC_CHAIN)

	full: BOOLEAN is False
			-- Is structured filled to capacity? (Answer: no.)
			-- (from EV_DYNAMIC_LIST)

	is_empty: BOOLEAN
			-- Is structure empty?
			-- (from FINITE)
		require -- from  CONTAINER
			True

	is_inserted (v: EV_TREE_NODE): BOOLEAN
			-- Has `v' been inserted by the most recent insertion?
			-- (By default, the value returned is equivalent to calling 
			-- `has (v)'. However, descendants might be able to provide more
			-- efficient implementations.)
			-- (from COLLECTION)

	isfirst: BOOLEAN
			-- Is cursor at first position?
			-- (from CHAIN)
		ensure -- from CHAIN
			valid_position: Result implies not is_empty

	islast: BOOLEAN
			-- Is cursor at last position?
			-- (from CHAIN)
		ensure -- from CHAIN
			valid_position: Result implies not is_empty

	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 CHAIN)
		require -- from  TRAVERSABLE
			True

	parent: EV_ANY
			-- The parent that `Current' is contained within, if any.
			-- (from EV_CONTAINABLE)
		require -- from EV_CONTAINABLE
			not_destroyed: not is_destroyed

	prunable: BOOLEAN
			-- May items be removed? (Answer: yes.)
			-- (from DYNAMIC_CHAIN)
		require -- from  COLLECTION
			True

	readable: BOOLEAN
			-- Is there a current item that may be read?
			-- (from SEQUENCE)
		require -- from  ACTIVE
			True

	same_type (other: ANY): BOOLEAN
			-- Is type of current object identical to type of `other'?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		ensure -- from ANY
			definition: Result = (conforms_to (other) and other.conforms_to (Current))

	valid_cursor (p: CURSOR): BOOLEAN
			-- Can the cursor be moved to position `p'?
			-- This is True if `p' conforms to EV_DYNAMIC_LIST_CURSOR and
			-- if it points to an item, `Current' must have it.
			-- (from EV_DYNAMIC_LIST)
		require -- from  CURSOR_STRUCTURE
			True
		ensure then -- from EV_DYNAMIC_LIST
			bridge_ok: Result = implementation.valid_cursor (p)

	valid_cursor_index (i: INTEGER_32): BOOLEAN
			-- Is `i' correctly bounded for cursor movement?
			-- (from CHAIN)
		ensure -- from CHAIN
			valid_cursor_index_definition: Result = ((i >= 0) and (i <= count + 1))

	valid_index (i: INTEGER_32): BOOLEAN
			-- Is `i' within allowable bounds?
			-- (from CHAIN)
		require -- from  TABLE
			True
		ensure then -- from INDEXABLE
			only_if_in_index_set: Result implies ((i >= index_set.lower) and (i <= index_set.upper))
		ensure then -- from CHAIN
			valid_index_definition: Result = ((i >= 1) and (i <= count))

	writable: BOOLEAN
			-- Is there a current item that may be modified?
			-- (from SEQUENCE)
		require -- from  ACTIVE
			True
	
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: 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: changeable_comparison_criterion
		ensure -- from CONTAINER
			reference_comparison: not object_comparison
	
feature -- Cursor movement

	back
			-- Move to previous position.
			-- (from EV_DYNAMIC_LIST)
		require -- from BILINEAR
			not_before: not before

	finish
			-- Move cursor to last position.
			-- (No effect if empty)
			-- (from CHAIN)
		require -- from  LINEAR
			True
		ensure then -- from CHAIN
			at_last: not is_empty implies islast

	forth
			-- Move cursor to next position.
			-- (from EV_DYNAMIC_LIST)
		require -- from LINEAR
			not_after: not after
		ensure then -- from LIST
			moved_forth: index = old index + 1

	go_i_th (i: INTEGER_32)
			-- Move cursor to `i'-th position.
			-- (from EV_DYNAMIC_LIST)
		require -- from CHAIN
			valid_cursor_index: valid_cursor_index (i)
		ensure -- from CHAIN
			position_expected: index = i

	go_to (p: CURSOR)
			-- Move cursor to position `p'.
			-- (from EV_DYNAMIC_LIST)
		require -- from CURSOR_STRUCTURE
			cursor_position_valid: valid_cursor (p)

	move (i: INTEGER_32)
			-- Move cursor `i' positions.
			-- (from EV_DYNAMIC_LIST)
		ensure -- from CHAIN
			too_far_right: (old index + i > count) implies exhausted
			too_far_left: (old index + i < 1) implies exhausted
			expected_index: (not exhausted) implies (index = old index + i)

	search (v: like item)
			-- Move to first position (at or after current
			-- position) where item and `v' are equal.
			-- If structure does not include `v' ensure that
			-- exhausted will be true.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from BILINEAR)
		ensure -- from LINEAR
			object_found: (not exhausted and object_comparison) implies equal (v, item)
			item_found: (not exhausted and not object_comparison) implies v = item

	start
			-- Move cursor to first position.
			-- (from EV_DYNAMIC_LIST)
		require -- from  TRAVERSABLE
			True
		ensure then -- from CHAIN
			at_first: not is_empty implies isfirst
		ensure then -- from EV_DYNAMIC_LIST
			empty_implies_after: is_empty implies after
	
feature -- Element change

	append (s: SEQUENCE [like item])
			-- Append a copy of `s'. Do not move cursor.
			-- (from EV_DYNAMIC_LIST)
		require -- from EV_DYNAMIC_LIST
			not_destroyed: not is_destroyed
			extendible: extendible
			sequence_not_void: s /= Void
			sequence_not_current: s /= Current
			not_parented: not s.there_exists (agent (v: like item): BOOLEAN
			)
		ensure -- from EV_DYNAMIC_LIST
			count_increased: old count + s.count = count
			cursor_not_moved: (index = old index) or (after and old after)

	extend (v: like item)
			-- Add `v' to end. Do not move cursor.
			-- Was declared in EV_DYNAMIC_LIST as synonym of force.
			-- (from EV_DYNAMIC_LIST)
		require -- from EV_DYNAMIC_LIST
			not_destroyed: not is_destroyed
			extendible: extendible
			v_not_void: v /= Void
			v_parent_void: v.parent = Void
			v_not_current: not same (v)
			v_not_parent_of_current: not is_parent_recursive (v)
		ensure -- from EV_DYNAMIC_LIST
			parent_is_current: v.parent = Current
			v_is_last: v = last
			count_increased: count = old count + 1
			cursor_not_moved: (index = old index) or (after and old after)

	fill (other: CONTAINER [EV_TREE_NODE])
			-- Fill with as many items of `other' as possible.
			-- The representations of `other' and current structure
			-- need not be the same.
			-- (from CHAIN)
		require -- from COLLECTION
			other_not_void: other /= Void
			extendible: extendible

	force (v: like item)
			-- Add `v' to end. Do not move cursor.
			-- Was declared in EV_DYNAMIC_LIST as synonym of extend.
			-- (from EV_DYNAMIC_LIST)
		require -- from EV_DYNAMIC_LIST
			not_destroyed: not is_destroyed
			extendible: extendible
			v_not_void: v /= Void
			v_parent_void: v.parent = Void
			v_not_current: not same (v)
			v_not_parent_of_current: not is_parent_recursive (v)
		ensure -- from EV_DYNAMIC_LIST
			parent_is_current: v.parent = Current
			v_is_last: v = last
			count_increased: count = old count + 1
			cursor_not_moved: (index = old index) or (after and old after)

	dl_force (v: like item)
			-- Add `v' to end.
			-- (from SEQUENCE)
		require -- from SEQUENCE
			extendible: extendible
		ensure then -- from SEQUENCE
			new_count: count = old count + 1
			item_inserted: has (v)

	merge_left (other: like Current)
			-- Merge `other' into current structure before cursor
			-- position. Do not move cursor. Empty `other'.
			-- (from EV_DYNAMIC_LIST)
		require -- from DYNAMIC_CHAIN
			extendible: extendible
			not_before: not before
			other_exists: other /= Void
			not_current: other /= Current
		ensure -- from DYNAMIC_CHAIN
			new_count: count = old count + old other.count
			new_index: index = old index + old other.count
			other_is_empty: other.is_empty

	merge_right (other: like Current)
			-- Merge `other' into current structure after cursor
			-- position. Do not move cursor. Empty `other'.
			-- (from EV_DYNAMIC_LIST)
		require -- from DYNAMIC_CHAIN
			extendible: extendible
			not_after: not after
			other_exists: other /= Void
			not_current: other /= Current
		ensure -- from DYNAMIC_CHAIN
			new_count: count = old count + old other.count
			same_index: index = old index
			other_is_empty: other.is_empty

	put (v: like item)
			-- Replace current item by `v'.
			-- (Synonym for replace)
			-- (from CHAIN)
		require -- from COLLECTION
			extendible: extendible
		ensure -- from COLLECTION
			item_inserted: is_inserted (v)
		ensure then -- from SET
			in_set_already: old has (v) implies (count = old count)
			added_to_set: not old has (v) implies (count = old count + 1)
		ensure then -- from CHAIN
			same_count: count = old count

	put_front (v: like item)
			-- Add `v' at beginning. Do not move cursor.
			-- (from EV_DYNAMIC_LIST)
		require -- from EV_DYNAMIC_LIST
			not_destroyed: not is_destroyed
			extendible: extendible
			v_not_void: v /= Void
			v_parent_void: v.parent = Void
			v_not_current: not same (v)
			v_not_parent_of_current: not is_parent_recursive (v)
		ensure -- from EV_DYNAMIC_LIST
			parent_is_current: v.parent = Current
			v_is_first: v = first
			count_increased: count = old count + 1
			cursor_not_moved: (index = old index + 1) or (before and old before)

	put_i_th (v: like item; i: INTEGER_32)
			-- Replace item at `i'-th position by `v'.
			-- (from EV_DYNAMIC_LIST)
		require -- from EV_DYNAMIC_LIST
			not_destroyed: not is_destroyed
			valid_index: i > 0 and i <= count
			v_not_void: v /= Void
			v_parent_void: v.parent = Void
			v_not_current: not same (v)
			v_not_parent_of_current: not is_parent_recursive (v)
		ensure -- from EV_DYNAMIC_LIST
			parent_is_current: v.parent = Current
			item_replaced: v = i_th (i)
			not_has_old_item: not has (old i_th (i))
			old_item_parent_void: (old i_th (i)).parent = Void
			count_same: count = old count
			cursor_not_moved: index = old index

	put_left (v: like item)
			-- Add `v' to the left of cursor position. Do not move cursor.
			-- (from EV_DYNAMIC_LIST)
		require -- from EV_DYNAMIC_LIST
			not_destroyed: not is_destroyed
			extendible: extendible
			not_before: not before
			v_not_void: v /= Void
			v_parent_void: v.parent = Void
			v_not_current: not same (v)
			v_not_parent_of_current: not is_parent_recursive (v)
		ensure -- from EV_DYNAMIC_LIST
			parent_is_current: v.parent = Current
			v_at_index_plus_one: v = i_th (index - 1)
			count_increased: count = old count + 1
			cursor_not_moved: index = old index + 1

	put_right (v: like item)
			-- Add `v' to right of cursor position. Do not move cursor.
			-- (from EV_DYNAMIC_LIST)
		require -- from EV_DYNAMIC_LIST
			not_destroyed: not is_destroyed
			extendible: extendible
			not_after: not after
			v_not_void: v /= Void
			v_parent_void: v.parent = Void
			v_not_current: not same (v)
			v_not_parent_of_current: not is_parent_recursive (v)
		ensure -- from EV_DYNAMIC_LIST
			parent_is_current: v.parent = Current
			v_at_index_plus_one: v = i_th (index + 1)
			count_increased: count = old count + 1
			cursor_not_moved: index = old index

	replace (v: like item)
			-- Replace current item by `v'.
			-- (from EV_DYNAMIC_LIST)
		require -- from EV_DYNAMIC_LIST
			not_destroyed: not is_destroyed
			writable: writable
			v_not_void: v /= Void
			v_parent_void: v.parent = Void
			v_not_current: not same (v)
			v_not_parent_of_current: not is_parent_recursive (v)
		ensure -- from EV_DYNAMIC_LIST
			parent_is_current: v.parent = Current
			item_replaced: v = item
			not_has_old_item: not has (old item)
			old_item_parent_void: (old item).parent = Void
			count_same: count = old count
			cursor_not_moved: index = old index

	set_data (some_data: like data)
			-- Assign `some_data' to data.
			-- (from EV_ANY)
		require -- from EV_ANY
			not_destroyed: not is_destroyed
		ensure -- from EV_ANY
			data_assigned: data = some_data

	swap (i: INTEGER_32)
			-- Exchange_item at `i'-th position with item
			-- at cursor position.
			-- (from EV_DYNAMIC_LIST)
		require -- from CHAIN
			not_off: not off
			valid_index: valid_index (i)
		ensure -- from CHAIN
			swapped_to_item: item = old i_th (i)
			swapped_from_item: i_th (i) = old item
	
feature -- Removal

	prune (v: like item)
			-- Remove `v' if present. Do not move cursor, except if
			-- cursor was on `v', move to right neighbor.
			-- (from EV_DYNAMIC_LIST)
		require -- from COLLECTION
			prunable: prunable
		ensure then -- from SET
			removed_count_change: old has (v) implies (count = old count - 1)
			not_removed_no_count_change: not old has (v) implies (count = old count)
			item_deleted: not has (v)
		ensure then -- from EV_DYNAMIC_LIST
			not_has_v: not has (v)
			had_item_implies_parent_void: old has (v) implies v.parent = Void
			had_item_implies_count_decreased: old has (v) implies count = old count - 1
			had_item_and_was_after_implies_index_decreased: (old after and old has (v)) implies index = old index - 1

	prune_all (v: like item)
			-- Remove all occurrences of `v'.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- Leave structure exhausted.
			-- (from DYNAMIC_CHAIN)
		require -- from COLLECTION
			prunable: prunable
		ensure -- from COLLECTION
			no_more_occurrences: not has (v)
		ensure then -- from DYNAMIC_CHAIN
			is_exhausted: exhausted

	remove
			-- Remove current item. Move cursor to right neighbor.
			-- (or after if no right neighbor).
			-- (from EV_DYNAMIC_LIST)
		require -- from ACTIVE
			prunable: prunable
			writable: writable
		ensure then -- from DYNAMIC_LIST
			after_when_empty: is_empty implies after
		ensure then -- from EV_DYNAMIC_LIST
			v_removed: not has (old item)
			parent_void: (old item).parent = Void
			count_decreased: count = old count - 1
			index_same: index = old index

	remove_left
			-- Remove item to left of cursor position.
			-- Do not move cursor.
			-- (from EV_DYNAMIC_LIST)
		require -- from DYNAMIC_CHAIN
			left_exists: index > 1
		ensure -- from DYNAMIC_CHAIN
			new_count: count = old count - 1
			new_index: index = old index - 1
		ensure then -- from EV_DYNAMIC_LIST
			left_neighbor_removed: not has (old i_th (index - 1))
			parent_void: (old i_th (index - 1)).parent = Void
			index_decreased: index = old index - 1

	remove_right
			-- Remove item to right of cursor position.
			-- Do not move cursor.
			-- (from EV_DYNAMIC_LIST)
		require -- from DYNAMIC_CHAIN
			right_exists: index < count
		ensure -- from DYNAMIC_CHAIN
			new_count: count = old count - 1
			same_index: index = old index
		ensure then -- from EV_DYNAMIC_LIST
			right_neighbor_removed: not has (old i_th (index + 1))
			parent_void: (old i_th (index + 1)).parent = Void
			index_same: index = old index

	wipe_out
			-- Remove all items.
			-- (from EV_DYNAMIC_LIST)
		require -- from COLLECTION
			prunable: prunable
		ensure -- from COLLECTION
			wiped_out: is_empty
		ensure then -- from DYNAMIC_LIST
			is_before: before
	
feature -- Conversion

	linear_representation: LINEAR [EV_TREE_NODE]
			-- Representation as a linear structure
			-- (from LINEAR)
		require -- from  CONTAINER
			True
	
feature -- Duplication

	copy (other: like Current)
			-- Update current object using fields of object attached
			-- to `other', so as to yield equal objects.
			-- (from EV_ANY)
		require -- from ANY
			other_not_void: other /= Void
			type_identity: same_type (other)
		ensure -- from ANY
			is_equal: is_equal (other)

	frozen deep_copy (other: like Current)
			-- Effect equivalent to that of:
			--		copy (`other' . deep_twin)
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		ensure -- from ANY
			deep_equal: deep_equal (Current, other)

	frozen deep_twin: like Current
			-- New object structure recursively duplicated from Current.
			-- (from ANY)
		ensure -- from ANY
			deep_equal: deep_equal (Current, Result)

	frozen standard_copy (other: like Current)
			-- Copy every field of `other' onto corresponding field
			-- of current object.
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
			type_identity: same_type (other)
		ensure -- from ANY
			is_standard_equal: standard_is_equal (other)

	frozen standard_twin: like Current
			-- New object field-by-field identical to `other'.
			-- Always uses default copying semantics.
			-- (from ANY)
		ensure -- from ANY
			standard_twin_not_void: Result /= Void
			equal: standard_equal (Result, Current)

	frozen twin: like Current
			-- New object equal to `Current'
			-- twin calls copy; to change copying/twining semantics, redefine copy.
			-- (from ANY)
		ensure -- from ANY
			twin_not_void: Result /= Void
			is_equal: Result.is_equal (Current)
	
feature -- Basic operations

	frozen default: like Current
			-- Default value of object's type
			-- (from ANY)

	frozen default_pointer: POINTER
			-- Default value of type `POINTER'
			-- (Avoid the need to write `p'.default for
			-- some `p' of type `POINTER'.)
			-- (from ANY)

	default_rescue
			-- Process exception for routines with no Rescue clause.
			-- (Default: do nothing.)
			-- (from ANY)

	frozen do_nothing
			-- Execute a null action.
			-- (from ANY)
	
feature -- Implementation

	changeable_comparison_criterion: BOOLEAN is False
			-- May object_comparison be changed?
			-- (Answer: no by default.
			-- (from EV_ITEM_LIST)
	
feature -- Basic operation

	recursive_do_all (action: PROCEDURE [ANY, TUPLE [EV_TREE_NODE]])
			-- Apply `action' to every item.
			-- Semantics not guaranteed if `action' changes the structure;
		require
			action_not_void: action /= Void
	
feature -- Command

	destroy
			-- Destroy underlying native toolkit object.
			-- Render `Current' unusable.
			-- (from EV_ANY)
		ensure -- from EV_ANY
			is_destroyed: is_destroyed
	
feature -- Contract support

	is_parent_recursive (a_list: like item): BOOLEAN
			-- Is `a_list' a parent of `Current'?
			-- (from EV_DYNAMIC_LIST)
		require -- from EV_DYNAMIC_LIST
			a_list_not_void: a_list /= Void
			not_destroyed: not is_destroyed

	same (other: EV_ANY): BOOLEAN
			-- Is `other' `Current'?
			-- (from EV_DYNAMIC_LIST)
	
feature -- Iteration

	do_all (action: PROCEDURE [ANY, TUPLE [EV_TREE_NODE]])
			-- 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 LINEAR)
		require -- from TRAVERSABLE
			action_exists: action /= Void

	do_if (action: PROCEDURE [ANY, TUPLE [EV_TREE_NODE]]; test: FUNCTION [ANY, TUPLE [EV_TREE_NODE], 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 LINEAR)
		require -- from TRAVERSABLE
			action_exists: action /= Void
			test_exits: test /= Void

	for_all (test: FUNCTION [ANY, TUPLE [EV_TREE_NODE], BOOLEAN]): BOOLEAN
			-- Is `test' true for all items?
			-- Semantics not guaranteed if `test' changes the structure;
			-- in such a case, apply iterator to clone of structure instead.
			-- (from LINEAR)
		require -- from TRAVERSABLE
			test_exits: test /= Void
		ensure then -- from LINEAR
			empty: is_empty implies Result

	there_exists (test: FUNCTION [ANY, TUPLE [EV_TREE_NODE], BOOLEAN]): BOOLEAN
			-- Is `test' true for at least one item?
			-- Semantics not guaranteed if `test' changes the structure;
			-- in such a case, apply iterator to clone of structure instead.
			-- (from LINEAR)
		require -- from TRAVERSABLE
			test_exits: test /= Void
	
feature -- Output

	io: STD_FILES
			-- Handle to standard file setup
			-- (from ANY)

	out: STRING_8
			-- New string containing terse printable representation
			-- of current object
			-- Was declared in ANY as synonym of tagged_out.
			-- (from ANY)

	print (some: ANY)
			-- Write terse external representation of `some'
			-- on standard output.
			-- (from ANY)

	frozen tagged_out: STRING_8
			-- New string containing terse printable representation
			-- of current object
			-- Was declared in ANY as synonym of out.
			-- (from ANY)
	
feature -- Platform

	operating_environment: OPERATING_ENVIRONMENT
			-- Objects available from the operating system
			-- (from ANY)
	
feature -- Status Report

	is_destroyed: BOOLEAN
			-- Is `Current' no longer usable?
			-- (from EV_ANY)
		ensure -- from EV_ANY
			bridge_ok: Result = implementation.is_destroyed
	
invariant
		-- from EV_ITEM_LIST
	parent_of_items_is_current: is_usable and then not is_empty implies parent_of_items_is_current
	items_unique: is_usable and not is_empty implies items_unique

		-- from EV_ANY
	is_initialized: is_initialized
	is_coupled: implementation /= Void and then implementation.interface = Current
	default_create_called: default_create_called

		-- from ANY
	reflexive_equality: standard_is_equal (Current)
	reflexive_conformance: conforms_to (Current)

		-- from LIST
	before_definition: before = (index = 0)
	after_definition: after = (index = count + 1)

		-- from CHAIN
	non_negative_index: index >= 0
	index_small_enough: index <= count + 1
	off_definition: off = ((index = 0) or (index = count + 1))
	isfirst_definition: isfirst = ((not is_empty) and (index = 1))
	islast_definition: islast = ((not is_empty) and (index = count))
	item_corresponds_to_index: (not off) implies (item = i_th (index))
	index_set_has_same_count: index_set.count = count

		-- from ACTIVE
	writable_constraint: writable implies readable
	empty_constraint: is_empty implies (not readable) and (not writable)

		-- from INDEXABLE
	index_set_not_void: index_set /= Void

		-- from BILINEAR
	not_both: not (after and before)
	before_constraint: before implies off

		-- from LINEAR
	after_constraint: after implies off

		-- from TRAVERSABLE
	empty_constraint: is_empty implies off

		-- from FINITE
	empty_definition: is_empty = (count = 0)
	non_negative_count: count >= 0

		-- from DYNAMIC_CHAIN
	extendible: extendible

indexing
	copyright: "Copyright (c) 1984-2006, Eiffel Software and others"
	license: "Eiffel Forum License v2 (see http://www.eiffel.com/licensing/forum.txt)"
	source: "[
		Eiffel Software
		356 Storke Road, Goleta, CA 93117 USA
		Telephone 805-685-1006, Fax 805-685-6869
		Website http://www.eiffel.com
		Customer support http://support.eiffel.com
	]"

end -- class EV_TREE_NODE_LIST