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

class 
	BOUNDED_QUEUE [G]

create 
	make

feature -- Initialization

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

	has (v: like item): BOOLEAN is
			-- Does queue include v?
			-- (Reference or object equality,
			-- based on object_comparison.)
		local
			i: INTEGER
		do
			if object_comparison then
				if v /= void then
					if out_index > in_index then
						from
							i := out_index
						until
							Result or i > fl.count
						loop
							Result := fl.item (i) /= void and then v.is_equal (fl.item (i))
							i := i + 1
						end
						from
							i := 0
						until
							Result or i >= in_index
						loop
							Result := fl.item (i) /= void and then v.is_equal (fl.item (i))
							i := i + 1
						end
					else
						from
							i := out_index
						until
							Result or i >= in_index
						loop
							Result := fl.item (i) /= void and then v.is_equal (fl.item (i))
							i := i + 1
						end
					end
				end
			else
				if out_index > in_index then
					from
						i := out_index
					until
						Result or i > fl.count
					loop
						Result := v = fl.item (i)
						i := i + 1
					end
					from
						i := 0
					until
						Result or i >= in_index
					loop
						Result := v = fl.item (i)
						i := i + 1
					end
				else
					from
						i := out_index
					until
						Result or i >= in_index
					loop
						Result := v = fl.item (i)
						i := i + 1
					end
				end
			end
		ensure -- from CONTAINER
			not_found_in_empty: Result implies not is_empty
		end

	item: G is
			-- Oldest item.
		require -- from ACTIVE
			readable: readable
		do
			Result := fl.item (out_index)
		end
	
feature -- Measurement

	capacity: INTEGER is
			-- Number of items that may be kept.
		do
			Result := fl.capacity - 1
		end

	count: INTEGER is
			-- Number of items.
		local
			size: INTEGER
		do
			size := fl.capacity
			Result := (in_index - out_index + size) \\ size
		end

	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
		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)

	off: BOOLEAN is
			-- Is there no current item?
		local
			size: INTEGER
		do
			if index = in_index then
				Result := True
			else
				size := fl.capacity
				Result := count <= ((index - out_index + size) \\ size)
			end
		end

	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 -- Cursor movement

	finish is
			-- Move cursor to last position.
		local
			size: INTEGER
		do
			if is_empty then
				index := 0
			else
				size := fl.capacity
				index := (in_index - 1 + size) \\ size
			end
		end

	forth is
			-- Move cursor to next position.
		do
			index := (index + 1) \\ fl.capacity
		end

	start is
			-- Move cursor to first position.
		do
			index := out_index
		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: G) is
			-- Add v as newest element.
			-- Was declared in BOUNDED_QUEUE as synonym of force and put.
		require -- from COLLECTION
			extendible: extendible
		do
			fl.put (v, in_index)
			in_index := (in_index + 1) \\ fl.capacity
		ensure -- from COLLECTION
			item_inserted: is_inserted (v)
		ensure then -- from BAG
			one_more_occurrence: occurrences (v) = old (occurrences (v)) + 1
		end

	fill (other: CONTAINER [G]) is
			-- Fill with as many items of other as possible.
			-- The representations of other and current structure
			-- need not be the same.
			-- (from COLLECTION)
		require -- from COLLECTION
			other_not_void: other /= void
			extendible
		local
			lin_rep: LINEAR [G]
		do
			lin_rep := other.linear_representation
			from
				lin_rep.start
			until
				not extendible or else lin_rep.off
			loop
				extend (lin_rep.item)
				lin_rep.forth
			end
		end

	force (v: G) is
			-- Add v as newest element.
			-- Was declared in BOUNDED_QUEUE as synonym of extend and put.
		do
			fl.put (v, in_index)
			in_index := (in_index + 1) \\ fl.capacity
		end

	put (v: G) is
			-- Add v as newest element.
			-- Was declared in BOUNDED_QUEUE as synonym of extend and force.
		require -- from COLLECTION
			extendible: extendible
		do
			fl.put (v, in_index)
			in_index := (in_index + 1) \\ fl.capacity
		ensure -- from COLLECTION
			item_inserted: is_inserted (v)
		end

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

	prune (v: like item) is
		require -- from COLLECTION
			prunable: prunable
		do
		end

	remove is
			-- Remove oldest item.
		require -- from ACTIVE
			prunable: prunable
			writable: writable
		do
			out_index := (out_index + 1) \\ fl.capacity
		end

	wipe_out is
			-- Remove all items.
		require -- from COLLECTION
			prunable
		do
			out_index := 0
			in_index := 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 original insertion order)
		local
			i: INTEGER
		do
			create Result.make (count)
			if out_index > in_index then
				from
					i := out_index
				until
					i >= fl.count
				loop
					Result.extend (fl.item (i))
					i := i + 1
				end
				from
					i := 1
				until
					i >= in_index
				loop
					Result.extend (fl.item (i))
					i := i + 1
				end
			else
				from
					i := out_index
				until
					i >= in_index
				loop
					Result.extend (fl.item (i))
					i := i + 1
				end
			end
		end
	
feature {BOUNDED_QUEUE} -- Implementation

	fl: ARRAY [G]
			-- Storage

	in_index: INTEGER
			-- Position for next insertion

	index: INTEGER
			-- Current position

	out_index: INTEGER
			-- Position of oldest item
	
invariant

	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_QUEUE


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