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	description: "Stacks with a bounded physical size, implemented by arrays"
	status: "See notice at end of class"
	names: dispenser, array
	representation: array
	access: fixed, lifo, membership
	size: fixed
	contents: generic
	date: "$Date: 2001-11-16 20:32:23 +0000 (Fri, 16 Nov 2001) $"
	revision: "$Revision: 51435 $"

class 
	BOUNDED_STACK [G]

create 
	make

feature -- Initialization

	make (n: INTEGER) is
			-- Create a stack for at most n items.
		require
			non_negative_argument: n >= 0
		do
			create fl.make (0, n)
		ensure
			stack_allocated: capacity = n
			empty_stack: count = 0
		end
	
feature -- Access

	has (v: G): BOOLEAN is
			-- Does v appear in stack?
			-- (Reference or object equality,
			-- based on object_comparison.)
		do
			if object_comparison then
				fl.compare_objects
			else
				fl.compare_references
			end
			Result := fl.has (v)
		ensure -- from CONTAINER
			not_found_in_empty: Result implies not is_empty
		end

	item: G is
			-- Last item pushed (i.e. top)
		require -- from ACTIVE
			readable: readable
		require else
			not_empty: count > 0
		do
			Result := fl.item (count)
		end
	
feature -- Measurement

	capacity: INTEGER is
		do
			Result := fl.count - 1
		end

	count: INTEGER

	occurrences (v: G): INTEGER is
		do
			if object_comparison then
				fl.compare_objects
			else
				fl.compare_references
			end
			Result := fl.occurrences (v)
		ensure -- from BAG
			non_negative_occurrences: Result >= 0
		end
	
feature -- Status report

	changeable_comparison_criterion: BOOLEAN is
			-- May object_comparison be changed?
			-- (Answer: yes by default.)
			-- (from CONTAINER)
		do
			Result := True
		end

	empty: BOOLEAN is
		obsolete "ELKS 2000: Use `is_empty' instead"
			-- Is there no element?
			-- (from CONTAINER)
		do
			Result := is_empty
		end

	extendible: BOOLEAN is
		do
			Result := not full
		ensure then
			Result = not full
		end

	full: BOOLEAN is
			-- Is structure full?
			-- (from BOUNDED)
		do
			Result := (count = capacity)
		end

	is_empty: BOOLEAN is
			-- Is structure empty?
			-- (from FINITE)
		do
			Result := (count = 0)
		end

	is_inserted (v: G): BOOLEAN is
			-- 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)
		do
			Result := has (v)
		end

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

	Prunable: BOOLEAN is True

	readable: BOOLEAN is
			-- Is there a current item that may be read?
			-- (from DISPENSER)
		do
			Result := not is_empty
		end

	Resizable: BOOLEAN is True

	writable: BOOLEAN is
			-- Is there a current item that may be modified?
			-- (from DISPENSER)
		do
			Result := not is_empty
		end
	
feature -- Status setting

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

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

	append (s: SEQUENCE [G]) is
			-- Append a copy of s.
			-- (Synonym for fill)
			-- (from DISPENSER)
		do
			fill (s)
		end

	extend (v: like item) is
			-- Push v on top.
			-- Was declared in BOUNDED_STACK as synonym of force and put.
		require -- from COLLECTION
			extendible: extendible
		do
			count := count + 1
			fl.put (v, count)
		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
		end

	fill (other: LINEAR [G]) is
			-- 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
		local
			temp: ARRAYED_STACK [G]
		do
			create temp.make (0)
			from
				other.start
			until
				other.off
			loop
				temp.extend (other.item)
				other.forth
			end
			from
			until
				temp.is_empty or else not extendible
			loop
				extend (temp.item)
				temp.remove
			end
		end

	force (v: like item) is
			-- Push v on top.
			-- Was declared in BOUNDED_STACK as synonym of extend and put.
		do
			count := count + 1
			fl.put (v, count)
		ensure then -- from STACK
			item_pushed: item = v
		end

	put (v: like item) is
			-- Push v on top.
			-- Was declared in BOUNDED_STACK as synonym of extend and force.
		require -- from COLLECTION
			extendible: extendible
		do
			count := count + 1
			fl.put (v, count)
		ensure -- from COLLECTION
			item_inserted: is_inserted (v)
		ensure then -- from STACK
			item_pushed: item = v
		end

	replace (v: like item) is
			-- Replace top item by v.
		require -- from ACTIVE
			writable: writable
		do
			fl.put (v, count)
		ensure -- from ACTIVE
			item_replaced: item = v
		end
	
feature -- Removal

	remove is
			-- Remove top item.
		require -- from ACTIVE
			prunable: prunable
			writable: writable
		require else
			not_empty: count /= 0
		local
			default_value: like item
		do
			fl.put (default_value, count)
			count := count - 1
		end

	wipe_out is
			-- Remove all items.
		require -- from COLLECTION
			prunable
		do
			fl.clear_all
			count := 0
		ensure -- from COLLECTION
			wiped_out: is_empty
		end
	
feature {NONE} -- Removal

	prune_all (v: G) is
			-- Remove all occurrences of v.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from COLLECTION)
		require -- from COLLECTION
			prunable
		do
			from
			until
				not has (v)
			loop
				prune (v)
			end
		ensure -- from COLLECTION
			no_more_occurrences: not has (v)
		end
	
feature -- Conversion

	linear_representation: ARRAYED_LIST [G] is
			-- Representation as a linear structure
			-- (in the reverse order of original insertion)
		local
			i: INTEGER
		do
			from
				create Result.make (count)
				i := count
			until
				i < 0
			loop
				Result.extend (fl.item (i))
				i := i - 1
			end
		end
	
feature {NONE} -- Inapplicable

	prune (v: G) is
		require -- from COLLECTION
			prunable: prunable
		do
		end
	
feature {STACK} -- Implementation

	finish is
			-- Move to last position.
			-- (No effect if empty)
		do
			if not is_empty then
				index := 1
			end
		end

	fl: ARRAY [G]
			-- Storage

	forth is
			-- Move to next position.
		do
			index := index - 1
		end

	index: INTEGER
			-- Current place in stack.

	off: BOOLEAN is
			-- Is there no current item?
		do
			Result := (index < 1) or else (index > count)
		end

	start is
			-- Move to first position.
			-- (No effect if empty)
		do
			if not is_empty then
				index := count
			end
		end
	
invariant

	count_small_enough: count <= capacity
	extendible_definition: extendible = not full
		-- 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 BOUNDED
	valid_count: count <= capacity
	full_definition: full = (count = capacity)

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 BOUNDED_STACK


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