indexing
	description: "Lists implemented by resizable arrays"
	legal: "See notice at end of class."
	status: "See notice at end of class."
	names: sequence
	representation: array
	access: index, cursor, membership
	size: fixed
	contents: generic
	date: "$Date: 2006-07-26 19:17:29 -0700 (Wed, 26 Jul 2006) $"
	revision: "$Revision: 61669 $"

class interface
	ARRAYED_LIST [G]

create 
	make (n: INTEGER_32)
			-- Allocate list with `n' items.
			-- (`n' may be zero for empty list.)
		require
			valid_number_of_items: n >= 0
		ensure
			correct_position: before
			is_empty: is_empty

	make_filled (n: INTEGER_32)
			-- Allocate list with `n' items.
			-- (`n' may be zero for empty list.)
			-- This list will be full.
		require
			valid_number_of_items: n >= 0
		ensure
			correct_position: before
			filled: full

	make_from_array (a: ARRAY [G])
			-- Create list from array `a'.
		require -- from ARRAY
			array_exists: a /= Void
		ensure then
			correct_position: before
			filled: count = a.count


create {ARRAYED_LIST}
	array_make (min_index, max_index: INTEGER_32)
			-- Allocate array; set index interval to
			-- `min_index' .. `max_index'; set all values to default.
			-- (Make array empty if `min_index' = `max_index' + 1).
			-- (from ARRAY)
		require -- from ARRAY
			valid_bounds: min_index <= max_index + 1
		ensure -- from ARRAY
			lower_set: lower = min_index
			upper_set: upper = max_index
			items_set: all_default

feature -- Initialization

	make (n: INTEGER_32)
			-- Allocate list with `n' items.
			-- (`n' may be zero for empty list.)
		require
			valid_number_of_items: n >= 0
		ensure
			correct_position: before
			is_empty: is_empty

	make_filled (n: INTEGER_32)
			-- Allocate list with `n' items.
			-- (`n' may be zero for empty list.)
			-- This list will be full.
		require
			valid_number_of_items: n >= 0
		ensure
			correct_position: before
			filled: full

	make_from_array (a: ARRAY [G])
			-- Create list from array `a'.
		require -- from ARRAY
			array_exists: a /= Void
		ensure then
			correct_position: before
			filled: count = a.count
	
feature -- Access

	cursor: ARRAYED_LIST_CURSOR
			-- Current cursor position
		ensure -- from CURSOR_STRUCTURE
			cursor_not_void: Result /= Void

	first: like item
			-- Item at first position
		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 current include `v'?
			-- (Reference or object equality,
			-- based on object_comparison.)
		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 ARRAYED_LIST as synonym of infix "@".
		require -- from TABLE
			valid_key: valid_index (i)

	index: INTEGER_32
			-- Index of item, if valid.

	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
		require -- from TRAVERSABLE
			not_off: not off
		require -- from ACTIVE
			readable: readable
		require else
			index_is_valid: valid_index (index)

	last: like first
			-- Item at last position
		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 ARRAYED_LIST as synonym of i_th.
		require -- from TABLE
			valid_key: valid_index (i)
	
feature -- Measurement

	count: INTEGER_32
			-- Number of items.

	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 {ANY} -- Measurement

	capacity: INTEGER_32
			-- Number of available indices
			-- Was declared in ARRAY as synonym of count.
			-- (from ARRAY)
		require -- from  BOUNDED
			True
		ensure then -- from ARRAY
			consistent_with_bounds: Result = upper - lower + 1
	
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

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

	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 structure filled to capacity?
		require -- from  BOX
			True

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

	is_inserted (v: G): BOOLEAN
			-- Has `v' been inserted at the end by the most recent put or
			-- extend?

	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

	prunable: BOOLEAN
			-- May items be removed? (Answer: yes.)
		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'?

	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' a valid index?
		require -- from  TABLE
			True
		require -- from  TO_SPECIAL
			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 cursor one position backward.
		require -- from BILINEAR
			not_before: not before

	finish
			-- Move cursor to last position if any.
		require -- from  LINEAR
			True
		ensure then -- from CHAIN
			at_last: not is_empty implies islast
		ensure then
			before_when_empty: is_empty implies before

	forth
			-- Move cursor one position forward.
		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.
		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'.
		require -- from CURSOR_STRUCTURE
			cursor_position_valid: valid_cursor (p)

	move (i: INTEGER_32)
			-- Move cursor `i' positions.
		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.)
		require -- from  LINEAR
			True
		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 if any.
		require -- from  TRAVERSABLE
			True
		ensure then -- from CHAIN
			at_first: not is_empty implies isfirst
		ensure then
			after_when_empty: is_empty implies after
	
feature -- Element change

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

	extend (v: like item)
			-- Add `v' to end.
			-- Do not move cursor.
			-- Was declared in ARRAYED_LIST as synonym of force.
		require -- from COLLECTION
			extendible: extendible
		ensure -- from COLLECTION
			item_inserted: is_inserted (v)
		ensure then -- from BAG
			one_more_occurrence: occurrences (v) = old (occurrences (v)) + 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.
			-- Do not move cursor.
			-- Was declared in ARRAYED_LIST as synonym of extend.
		require -- from SEQUENCE
			extendible: extendible
		ensure then -- from SEQUENCE
			new_count: count = old count + 1
			item_inserted: has (v)

	merge_left (other: ARRAYED_LIST [G])
			-- Merge `other' into current structure before cursor.
		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: ARRAYED_LIST [G])
			-- Merge `other' into current structure after cursor.
		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_i_th (v: like i_th; i: INTEGER_32)
			-- Replace `i'-th entry, if in index interval, by `v'.
			-- (from ARRAY)
		require -- from TABLE
			valid_key: valid_index (i)
		require -- from TO_SPECIAL
			valid_index: valid_index (i)
		ensure then -- from INDEXABLE
			insertion_done: i_th (i) = v
		ensure -- from TO_SPECIAL
			inserted: array_item (i) = v

	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 CHAIN
			same_count: count = old count

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

	put_left (v: like item)
			-- Add `v' to the left of current position.
			-- Do not move cursor.
		require -- from DYNAMIC_CHAIN
			extendible: extendible
			not_before: not before
		ensure -- from DYNAMIC_CHAIN
			new_count: count = old count + 1
			new_index: index = old index + 1

	put_right (v: like item)
			-- Add `v' to the right of current position.
			-- Do not move cursor.
		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

	replace (v: like first)
			-- Replace current item by `v'.
		require -- from ACTIVE
			writable: writable
		ensure -- from ACTIVE
			item_replaced: item = v
	
feature -- Removal

	prune (v: like item)
			-- Remove first occurrence of `v', if any,
			-- after cursor position.
			-- Move cursor to right neighbor.
			-- (or after if no right neighbor or `v' does not occur)
		require -- from COLLECTION
			prunable: prunable

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

	remove
			-- Remove current item.
			-- Move cursor to right neighbor
			-- (or after if no right neighbor)
		require -- from ACTIVE
			prunable: prunable
			writable: writable
		ensure then -- from DYNAMIC_LIST
			after_when_empty: is_empty implies after
		ensure then
			index: index = old index

	remove_left
			-- Remove item to the left of cursor position.
			-- Do not move cursor.
		require -- from DYNAMIC_CHAIN
			left_exists: index > 1
		ensure -- from DYNAMIC_CHAIN
			new_count: count = old count - 1
			new_index: index = old index - 1

	remove_right
			-- Remove item to the right of cursor position
			-- Do not move cursor
		require -- from DYNAMIC_CHAIN
			right_exists: index < count
		ensure -- from DYNAMIC_CHAIN
			new_count: count = old count - 1
			same_index: index = old index

	wipe_out
			-- Remove all items.
		require -- from COLLECTION
			prunable: prunable
		ensure -- from COLLECTION
			wiped_out: is_empty
		ensure then -- from DYNAMIC_LIST
			is_before: before
	
feature -- Resizing

	resize (new_capacity: INTEGER_32)
			-- Resize list so that it can contain
			-- at least `n' items. Do not lose any item.
		require
			new_capacity_large_enough: new_capacity >= capacity
		ensure
			capacity_set: capacity >= new_capacity
	
feature -- Transformation

	swap (i: INTEGER_32)
			-- Exchange item at `i'-th position with item
			-- at cursor position.
		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 -- Conversion

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

	copy (other: like Current)
			-- Reinitialize by copying all the items of `other'.
			-- (This is also used by clone.)
			-- (from ARRAY)
		require -- from ANY
			other_not_void: other /= Void
			type_identity: same_type (other)
		ensure -- from ANY
			is_equal: is_equal (other)
		ensure then -- from ARRAY
			equal_areas: area.is_equal (other.area)

	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-list beginning at current position
			-- and having min (`n', count - index + 1) items.
		require -- from CHAIN
			not_off_unless_after: off implies after
			valid_subchain: n >= 0

	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 -- 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 LINEAR)
		require -- from TRAVERSABLE
			action_exists: action /= Void
		require -- from ARRAY
			action_not_void: 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 LINEAR)
		require -- from TRAVERSABLE
			action_exists: action /= Void
			test_exits: test /= Void
		require -- from ARRAY
			action_not_void: action /= Void
			test_not_void: test /= Void

	for_all (test: FUNCTION [ANY, TUPLE [G], 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
		require -- from ARRAY
			test_not_void: test /= Void
		ensure then -- from LINEAR
			empty: is_empty implies Result

	there_exists (test: FUNCTION [ANY, TUPLE [G], 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
		require -- from ARRAY
			test_not_void: 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)
	
invariant
	prunable: prunable
	starts_from_one: lower = 1
	empty_means_storage_empty: is_empty implies all_default

		-- from ARRAY
	area_exists: area /= Void
	consistent_size: capacity = upper - lower + 1
	non_negative_count: count >= 0
	index_set_has_same_count: valid_index_set

		-- from RESIZABLE
	increase_by_at_least_one: minimal_increase >= 1

		-- from BOUNDED
	valid_count: count <= capacity
	full_definition: full = (count = capacity)

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

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

		-- from INDEXABLE
	index_set_not_void: index_set /= Void

		-- 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 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 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 ARRAYED_LIST