indexing
	description: "[
		Sets whose items may be compared according to a partial order relation
		implemented as sorted two-way lists.
	]"
	legal: "See notice at end of class."
	status: "See notice at end of class."
	names: sorted_set, set, two_way_list
	representation: linked
	access: membership, min, max
	contents: generic
	date: "$Date: 2006-01-22 18:25:44 -0800 (Sun, 22 Jan 2006) $"
	revision: "$Revision: 56675 $"

class interface
	PART_SORTED_SET [G -> PART_COMPARABLE]

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


create {PART_SORTED_SET}
	make_sublist (first_item, last_item: like first_element; n: INTEGER_32)
			-- Create sublist
			-- (from TWO_WAY_LIST)

feature -- Access

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

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

	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
	
feature -- Measurement

	count: INTEGER_32
			-- Number of items
			-- (from LINKED_LIST)
	
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)

	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))

	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

	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: 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 LINKED_LIST)

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

	changeable_comparison_criterion: BOOLEAN
			-- May object_comparison be changed?
			-- (Answer: yes by default.)
			-- (from CONTAINER)
		ensure then -- from SET
			only_on_empty: Result = is_empty

	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

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

	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)

	islast: BOOLEAN
			-- Is cursor at last position?
			-- (from TWO_WAY_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

	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_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))
	
feature {ANY} -- Status report

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

	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))

	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

	forth
			-- Move cursor to next position, if any.
			-- (from TWO_WAY_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

	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 {ANY} -- Cursor movement

	finish
			-- Move cursor to last position.
			-- (Go before if empty)
			-- (from TWO_WAY_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
		ensure then -- from TWO_WAY_LIST
			not_after: not after
	
feature -- Element change

	extend (v: G)
			-- Ensure that structure includes `v'.
			-- Was declared in PART_SORTED_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

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

	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 structure includes `v'.
			-- Was declared in PART_SORTED_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_left (v: like item)
			-- Add `v' to the left of cursor position.
			-- Do not move cursor.
			-- (from TWO_WAY_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 then -- from LINKED_LIST
			previous_exists: previous /= Void
			item_inserted: previous.item = v
		ensure -- from LINEAR_SUBSET
			cursor_position_unchanged: index = old index + 1
	
feature -- Removal

	prune (v: like item)
			-- Remove `v' if present.
		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)

	prune_all (v: like item)
			-- Remove all items identical to `v'.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- Leave cursor off.
			-- (from PART_SORTED_TWO_WAY_LIST)
		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 TWO_WAY_LIST)
		require -- from ACTIVE
			prunable: prunable
			writable: writable
		require -- from TRAVERSABLE_SUBSET
			not_off: not off
		ensure then -- from DYNAMIC_LIST
			after_when_empty: is_empty implies after

	wipe_out
			-- Remove all items.
			-- (from TWO_WAY_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 [G]
			-- 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 LINKED_LIST)
		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)

	duplicate (n: INTEGER_32): like Current
			-- Copy of sub-set beginning at cursor position
			-- and having min (`n', count - index + 1) items
		require -- from CHAIN
			not_off_unless_after: off implies after
			valid_subchain: n >= 0
		require -- from SUBSET
			non_negative: n >= 0
		ensure -- from SUBSET
			correct_count_1: n <= count implies Result.count = n
			correct_count_2: n >= count implies Result.count = count

	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)

	intersect (other: TRAVERSABLE_SUBSET [G])
			-- Remove all items not in `other'.
			-- No effect if `other' is_empty.
			-- (from TRAVERSABLE_SUBSET)
		require -- from SUBSET
			set_exists: other /= Void
			same_rule: object_comparison = other.object_comparison
		ensure -- from SUBSET
			is_subset_other: is_subset (other)

	subtract (other: TRAVERSABLE_SUBSET [G])
			-- Remove all items also in `other'.
			-- (from TRAVERSABLE_SUBSET)
		require -- from SUBSET
			set_exists: other /= Void
			same_rule: object_comparison = other.object_comparison
		ensure -- from SUBSET
			is_disjoint: disjoint (other)

	symdif (other: TRAVERSABLE_SUBSET [G])
			-- Remove all items also in `other', and add all
			-- items of `other' not already present.
			-- (from TRAVERSABLE_SUBSET)
		require -- from SUBSET
			set_exists: other /= Void
			same_rule: object_comparison = other.object_comparison
	
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)
	
invariant
		-- from LINEAR_SUBSET
	before_definition: before = (index = 0)

		-- from TRAVERSABLE_SUBSET
	empty_definition: is_empty = (count = 0)
	count_range: count >= 0

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

		-- from TWO_WAY_LIST
	non_empty_list_has_two_endpoints: not is_empty implies (first_element /= Void and last_element /= Void)
	first_element_constraint: first_element /= Void implies first_element.left = Void
	last_element_constraint: last_element /= Void implies last_element.right = Void

		-- from LINKED_LIST
	prunable: prunable
	empty_constraint: is_empty implies ((first_element = Void) and (active = Void))
	not_void_unless_empty: (active = Void) implies is_empty
	before_constraint: before implies (active = first_element)
	after_constraint: after implies (active = last_element)

		-- 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
	library: "EiffelBase: Library of reusable components for Eiffel."
	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 PART_SORTED_SET