indexing
	description: "Stacks implemented by resizable arrays"
	status: "See notice at end of class"
	names: dispenser, array
	representation: array
	access: fixed, lifo, membership
	size: fixed
	contents: generic
	date: "$Date$"
	revision: "$Revision$"

class interface
	ARRAYED_STACK [G]

create

	make (n: INTEGER)
			-- Allocate list with n items.
			-- (n may be zero for empty list.)
			-- (from ARRAYED_LIST)
		require -- from ARRAYED_LIST
			valid_number_of_items: n >= 0
		ensure -- from ARRAYED_LIST
			correct_position: after

feature  -- Initialization

	make (n: INTEGER)
			-- Allocate list with n items.
			-- (n may be zero for empty list.)
			-- (from ARRAYED_LIST)
		require -- from ARRAYED_LIST
			valid_number_of_items: n >= 0
		ensure -- from ARRAYED_LIST
			correct_position: after

feature -- Access

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

	item: like first
			-- Current item
			-- (from ARRAYED_LIST)
		require -- from TRAVERSABLE
			not_off: not off
		require -- from ACTIVE
			readable: readable
		require else -- from ARRAYED_LIST
			index_is_valid: valid_index (index)

feature -- Measurement

	count: INTEGER
			-- Number of items.
			-- (from ARRAYED_LIST)

	occurrences (v: like item): INTEGER
			-- Number of times v appears.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from CHAIN)
		ensure -- from BAG
			non_negative_occurrences: Result >= 0

	occurrences (v: like item): INTEGER
			-- Number of times v appears.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from CHAIN)
		ensure -- from BAG
			non_negative_occurrences: Result >= 0

feature -- Comparison

	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

feature -- Status report

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

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

	full: BOOLEAN
			-- Is structure filled to capacity?
			-- (from ARRAYED_LIST)

	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?
			-- (from ARRAYED_LIST)

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

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

	readable: BOOLEAN
			-- Is there a current item that may be read?
			-- (from DISPENSER)

	writable: BOOLEAN
			-- Is there a current item that may be modified?
			-- (from DISPENSER)

feature -- Status setting

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

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

feature -- Element change

	append (s: SEQUENCE [G])
			-- Append a copy of s.
			-- (Synonym for fill)
			-- (from DISPENSER)
		require -- from SEQUENCE
			argument_not_void: s /= void
		ensure -- from SEQUENCE
			new_count: count >= old count

	extend (v: like item)
			-- Push v on top.
			-- Was declared in ARRAYED_STACK as synonym of put and 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
		ensure then -- from STACK
			item_pushed: item = v

	fill (other: LINEAR [G])
			-- Fill with as many items of other as possible.
			-- Fill items with greatest index from other first.
			-- Items inserted with lowest index (from other) will
			-- always be on the top of stack.
			-- The representations of other and current structure
			-- need not be the same.
			-- (from STACK)
		require -- from COLLECTION
			other_not_void: other /= void
			extendible

	force (v: like item)
			-- Push v on top.
			-- Was declared in ARRAYED_STACK as synonym of extend and put.
		ensure then -- from STACK
			item_pushed: item = v

	put (v: like item)
			-- Push v on top.
			-- Was declared in ARRAYED_STACK as synonym of extend and force.
		require -- from COLLECTION
			extendible: extendible
		ensure -- from COLLECTION
			item_inserted: is_inserted (v)
		ensure then -- from STACK
			item_pushed: item = v

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

feature -- Removal

	remove
			-- Remove top item.
		require -- from ACTIVE
			prunable: prunable
			writable: writable
		require else
			not_empty: count /= 0

	wipe_out
			-- Remove all items.
			-- (from ARRAYED_LIST)
		require -- from COLLECTION
			prunable
		ensure -- from COLLECTION
			wiped_out: is_empty
		ensure then -- from DYNAMIC_LIST
			is_before: after

feature -- Conversion

	linear_representation: ARRAYED_LIST [G]
			-- Representation as a linear structure
			-- (in the reverse order of original insertion)

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)

invariant

		-- from ANY
	reflexive_equality: standard_is_equal (Current)
	reflexive_conformance: conforms_to (Current)
		-- from DISPENSER
	readable_definition: readable = not is_empty
	writable_definition: writable = not is_empty
		-- from ACTIVE
	writable_constraint: writable implies readable
	empty_constraint: is_empty implies (not readable) and (not writable)
		-- from FINITE
	empty_definition: is_empty = (count = 0)
	non_negative_count: count >= 0
		-- from ARRAYED_LIST
	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 INDEXABLE
	index_set_not_void: index_set /= void
		-- from LIST
	before_definition: after = (index = 0)
	after_definition: before = (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 BILINEAR
	not_both: not (before and after)
	before_constraint: after implies off
		-- from LINEAR
	after_constraint: before implies off
		-- from TRAVERSABLE
	empty_constraint: is_empty implies off
		-- from DYNAMIC_CHAIN
	extendible: extendible

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

end -- class ARRAYED_STACK