indexing
	description: "Sets implemented by linked lists"
	legal: "See notice at end of class."
	status: "See notice at end of class."
	names: linked_set, set, linked_list
	representation: linked
	access: membership
	contents: generic
	date: "$Date: 2007-01-14 01:47:13 -0800 (Sun, 14 Jan 2007) $"
	revision: "$Revision: 55 $"

class interface
	LINKED_SET [G]


create 
	make
			-- Create an empty list.
			-- (from LINKED_LIST)
		ensure -- from LINKED_LIST
			is_before: before

feature -- Access

	cursor: LINKED_LIST_CURSOR [G]
			-- Current cursor position
			-- (from LINKED_LIST)
		ensure -- from CURSOR_STRUCTURE
			cursor_not_void: Result /= Void

	first: like item
			-- Item at first position
			-- (from LINKED_LIST)
		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)
		ensure -- from ANY
			generating_type_not_void: Result /= Void
			generating_type_not_empty: not Result.is_empty

	generator: STRING_8
			-- Name of current object's generating class
			-- (base class of the type of which it is a direct instance)
			-- (from ANY)
		ensure -- from ANY
			generator_not_void: Result /= Void
			generator_not_empty: not Result.is_empty

	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

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

	index: INTEGER_32
			-- Index of current position
			-- (from LINKED_LIST)
		require -- from  LINEAR
			True
		require -- from  LINEAR_SUBSET
			True

	index_of (v: like item; i: INTEGER_32): INTEGER_32
			-- Index of `i'-th occurrence of item identical to `v'.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- 0 if none.
			-- (from CHAIN)
		require -- from LINEAR
			positive_occurrences: i > 0
		ensure -- from LINEAR
			non_negative_result: Result >= 0

	item: G
			-- Current item
			-- (from LINKED_LIST)
		require -- from TRAVERSABLE
			not_off: not off
		require -- from ACTIVE
			readable: readable
		require -- from TRAVERSABLE_SUBSET
			not_off: not off

	item_for_iteration: G
			-- Item at current position
			-- (from LINEAR)
		require -- from LINEAR
			not_off: not off

	last: like item
			-- Item at last position
			-- (from LINKED_LIST)
		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

	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 LINKED_LIST)

	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 (other /= Void and then some.same_type (other))
			symmetric: Result implies deep_equal (other, some)

	disjoint (other: TRAVERSABLE_SUBSET [G]): BOOLEAN
			-- Do current set and `other' have no
			-- items in common?
			-- (from TRAVERSABLE_SUBSET)
		require -- from SUBSET
			set_exists: other /= Void
			same_rule: object_comparison = other.object_comparison

	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))

	frozen is_deep_equal (other: LINKED_SET [G]): BOOLEAN
			-- Are `Current' and `other' attached to isomorphic object structures?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		ensure -- from ANY
			shallow_implies_deep: standard_is_equal (other) implies Result
			same_type: Result implies same_type (other)
			symmetric: Result implies other.is_deep_equal (Current)

	is_equal (other: LINKED_SET [G]): 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

	is_subset (other: TRAVERSABLE_SUBSET [G]): BOOLEAN
			-- Is current set a subset of `other'?
			-- (from TRAVERSABLE_SUBSET)
		require -- from SUBSET
			set_exists: other /= Void
			same_rule: object_comparison = other.object_comparison

	is_superset (other: SUBSET [G]): BOOLEAN
			-- Is current set a superset of `other'?
			-- (from SUBSET)
		require -- from SUBSET
			set_exists: other /= Void
			same_rule: object_comparison = other.object_comparison

	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: LINKED_SET [G]): 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 LINKED_LIST)

	before: BOOLEAN
			-- Is there no valid cursor position to the left of cursor?
			-- (from LINKED_LIST)

	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 LINKED_LIST)

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

	is_inserted (v: G): 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 LINKED_LIST)
		ensure -- from CHAIN
			valid_position: Result implies not is_empty

	islast: BOOLEAN
			-- Is cursor at last position?
			-- (from LINKED_LIST)
		require -- from  CHAIN
			True
		require -- from  LINEAR_SUBSET
			True
		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 LINKED_LIST)
		require -- from  TRAVERSABLE
			True
		require -- from  TRAVERSABLE_SUBSET
			True

	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 LINKED_LIST)
		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'?
			-- (from LINKED_LIST)

	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
		require -- from  LINEAR_SUBSET
			True
		ensure then -- from INDEXABLE
			only_if_in_index_set: Result implies ((i >= index_set.lower) and (i <= index_set.upper))
		ensure -- from LINEAR_SUBSET
			index_valid: 0 <= i and i <= count + 1
		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 item.
			-- (from LINKED_LIST)
		require -- from BILINEAR
			not_before: not before

	finish
			-- Move cursor to last position.
			-- (Go before if empty)
			-- (from LINKED_LIST)
		require -- from  LINEAR
			True
		ensure then -- from CHAIN
			at_last: not is_empty implies islast
		ensure then -- from LINKED_LIST
			empty_convention: is_empty implies before

	forth
			-- Move cursor to next position.
			-- (from LINKED_LIST)
		require -- from LINEAR
			not_after: not after
		require -- from TRAVERSABLE_SUBSET
			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 LINKED_LIST)
		require -- from CHAIN
			valid_cursor_index: valid_cursor_index (i)
		require -- from LINEAR_SUBSET
			valid_index: valid_index (i)
		ensure -- from CHAIN
			position_expected: index = i
		ensure -- from LINEAR_SUBSET
			cursor_moved: index = i

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

	move (i: INTEGER_32)
			-- Move cursor `i' positions. The cursor
			-- may end up off if the offset is too big.
			-- (from LINKED_LIST)
		require -- from  CHAIN
			True
		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)
		ensure then -- from LINKED_LIST
			moved_if_inbounds: ((old index + i) >= 0 and (old index + i) <= (count + 1)) implies index = (old index + i)
			before_set: (old index + i) <= 0 implies before
			after_set: (old index + i) >= (count + 1) implies after

	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 LINKED_LIST)
		require -- from  TRAVERSABLE
			True
		require -- from  TRAVERSABLE_SUBSET
			True
		ensure then -- from CHAIN
			at_first: not is_empty implies isfirst
		ensure then -- from LINKED_LIST
			empty_convention: is_empty implies after
	
feature -- Element change

	append (s: SEQUENCE [G])
			-- Append a copy of `s'.
			-- (from CHAIN)
		require -- from SEQUENCE
			argument_not_void: s /= Void
		ensure -- from SEQUENCE
			new_count: count >= old count

	extend (v: G)
			-- Ensure that set includes `v'.
			-- Was declared in LINKED_SET as synonym of put.
		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)

	fill (other: CONTAINER [G])
			-- 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.
			-- (from SEQUENCE)
		require -- from SEQUENCE
			extendible: extendible
		ensure then -- from SEQUENCE
			new_count: count = old count + 1
			item_inserted: has (v)

	merge (other: CONTAINER [G])
			-- Add all items of `other'.
			-- (from TRAVERSABLE_SUBSET)
		require -- from SUBSET
			set_exists: other /= Void
			same_rule: object_comparison = other.object_comparison

	merge_left (other: LINKED_SET [G])
			-- Merge `other' into current structure before cursor
			-- position. Do not move cursor. Empty `other'.
			-- (from LINKED_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: LINKED_SET [G])
			-- Merge `other' into current structure after cursor
			-- position. Do not move cursor. Empty `other'.
			-- (from LINKED_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

	move_item (v: G)
			-- Move `v' to the left of cursor.
			-- (from LINEAR_SUBSET)
		require -- from LINEAR_SUBSET
			item_exists: v /= Void
			item_in_set: has (v)

	put (v: G)
			-- Ensure that set includes `v'.
			-- Was declared in LINKED_SET as synonym of extend.
		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)

	put_front (v: like item)
			-- Add `v' to beginning.
			-- Do not move cursor.
			-- (from LINKED_LIST)
		ensure -- from DYNAMIC_CHAIN
			new_count: count = old count + 1
			item_inserted: first = v

	put_i_th (v: like item; i: INTEGER_32)
			-- Put `v' at `i'-th position.
			-- (from CHAIN)
		require -- from TABLE
			valid_key: valid_index (i)
		ensure then -- from INDEXABLE
			insertion_done: i_th (i) = v

	put_left (v: like item)
			-- Add `v' to the left of cursor position.
			-- Do not move cursor.
			-- (from LINKED_LIST)
		require -- from DYNAMIC_CHAIN
			extendible: extendible
			not_before: not before
		require -- from LINEAR_SUBSET
			item_exists: v /= Void
			not_before: not before
		ensure -- from DYNAMIC_CHAIN
			new_count: count = old count + 1
			new_index: index = old index + 1
		ensure -- from LINEAR_SUBSET
			cursor_position_unchanged: index = old index + 1
		ensure then -- from LINKED_LIST
			previous_exists: previous /= Void
			item_inserted: {q: like previous} previous and then q.item = v

	put_right (v: like item)
			-- Add `v' to the right of cursor position.
			-- Do not move cursor.
			-- (from LINKED_LIST)
		require -- from DYNAMIC_CHAIN
			extendible: extendible
			not_after: not after
		ensure -- from DYNAMIC_CHAIN
			new_count: count = old count + 1
			same_index: index = old index
		ensure then -- from LINKED_LIST
			next_exists: next /= Void
			item_inserted: not old before implies ({n: like next} next and then n.item = v)
			item_inserted_before: old before implies ({c: like active} active and then c.item = v)

	replace (v: like item)
			-- Replace current item by `v'.
			-- (from LINKED_LIST)