note
	description: "Unbounded queues, implemented by resizable arrays"
	library: "Free implementation of ELKS library"
	legal: "See notice at end of class."
	status: "See notice at end of class."
	names: dispenser, array
	representation: array
	access: fixed, fifo, membership
	size: fixed
	contents: generic
	date: "$Date: 2018-12-15 18:06:16 +0000 (Sat, 15 Dec 2018) $"
	revision: "$Revision: 102608 $"

class 
	ARRAYED_QUEUE [G]

create 
	make

feature {NONE} -- Initialization

	default_create
			-- Process instances of classes with no creation clause.
			-- (Default: do nothing.)
			-- (from ANY)
		do
		end

	make (n: INTEGER_32)
			-- Create queue for at most n items.
		require
			non_negative_argument: n >= 0
		do
			create area.make_empty (n)
			out_index := 1
			count := 0
		ensure
			capacity_expected: capacity = n
			is_empty: is_empty
		end
	
feature -- Access

	generating_type: TYPE [detachable ARRAYED_QUEUE [G]]
			-- Type of current object
			-- (type of which it is a direct instance)
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			generating_type_not_void: Result /= Void
		end

	generator: STRING_8
			-- Name of current object's generating class
			-- (base class of the type of which it is a direct instance)
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			generator_not_void: Result /= Void
			generator_not_empty: not Result.is_empty
		end

	has (v: like item): BOOLEAN
			-- Does queue include v?
			-- (Reference or object equality,
			-- based on object_comparison.)
		local
			i, j, nb: INTEGER_32
		do
			i := out_index - Lower
			j := count
			nb := area.capacity
			if object_comparison then
				from
				until
					j = 0 or v ~ area.item (i)
				loop
					i := i + 1
					if i = nb then
						i := 0
					end
					j := j - 1
				end
			else
				from
				until
					j = 0 or v = area.item (i)
				loop
					i := i + 1
					if i = nb then
						i := 0
					end
					j := j - 1
				end
			end
			Result := j > 0
		ensure -- from CONTAINER
			not_found_in_empty: Result implies not is_empty
		end

	item: G
			-- Oldest item.
		require -- from ACTIVE
			readable: readable
		do
			Result := area.item (out_index - Lower)
		end
	
feature {ARRAYED_QUEUE, ARRAYED_QUEUE_ITERATION_CURSOR} -- Access

	area: SPECIAL [G]
			-- Storage for queue.

	out_index: INTEGER_32
			-- Position of oldest item.
	
feature {ARRAYED_QUEUE_ITERATION_CURSOR} -- Access

	Lower: INTEGER_32 = 1
			-- Lower bound for accessing list items via indexes
	
feature -- Measurement

	additional_space: INTEGER_32
			-- Proposed number of additional items
			-- (from RESIZABLE)
		do
			Result := (capacity // 2).max (Minimal_increase)
		ensure -- from RESIZABLE
			at_least_one: Result >= 1
		end

	capacity: INTEGER_32
			-- Number of items that may be stored
		do
			Result := area.capacity
		ensure -- from BOUNDED
			capacity_non_negative: Result >= 0
		end

	count: INTEGER_32
			-- Number of items

	Growth_percentage: INTEGER_32 = 50
			-- Percentage by which structure will grow automatically
			-- (from RESIZABLE)

	index_set: INTEGER_INTERVAL
			-- Range of acceptable indexes
		do
			create Result.make (1, count)
		ensure then
			count_definition: Result.count = count
		end

	Minimal_increase: INTEGER_32 = 5
			-- Minimal number of additional items
			-- (from RESIZABLE)

	occurrences (v: G): INTEGER_32
			-- Number of times v appears in structure
			-- (Reference or object equality,
			-- based on object_comparison.)
		local
			i, j, nb: INTEGER_32
		do
			i := out_index - Lower
			j := count
			nb := area.capacity
			if object_comparison then
				from
				until
					j = 0
				loop
					if area.item (i) ~ v then
						Result := Result + 1
					end
					i := i + 1
					if i = nb then
						i := 0
					end
					j := j - 1
				end
			else
				from
				until
					j = 0
				loop
					if area.item (i) = v then
						Result := Result + 1
					end
					i := i + 1
					if i = nb then
						i := 0
					end
					j := j - 1
				end
			end
		ensure -- from BAG
			non_negative_occurrences: Result >= 0
		end
	
feature {NONE} -- Measurement

	estimated_count_of (other: ITERABLE [G]): INTEGER_32
			-- Estimated number of elements in other.
			-- (from CONTAINER)
		do
			if attached {FINITE [G]} other as f then
				Result := f.count
			elseif attached {READABLE_INDEXABLE [G]} other as r then
				Result := r.upper - r.lower + 1
			end
		ensure -- from CONTAINER
			instance_free: class
			non_negative_result: Result >= 0
		end
	
feature -- Comparison

	frozen deep_equal (a: detachable ANY; b: like arg #1): BOOLEAN
			-- Are a and b either both void
			-- or attached to isomorphic object structures?
			-- (from ANY)
		do
			if a = Void then
				Result := b = Void
			else
				Result := b /= Void and then a.is_deep_equal (b)
			end
		ensure -- from ANY
			instance_free: class
			shallow_implies_deep: standard_equal (a, b) implies Result
			both_or_none_void: (a = Void) implies (Result = (b = Void))
			same_type: (Result and (a /= Void)) implies (b /= Void and then a.same_type (b))
			symmetric: Result implies deep_equal (b, a)
		end

	frozen equal (a: detachable ANY; b: like arg #1): BOOLEAN
			-- Are a and b either both void or attached
			-- to objects considered equal?
			-- (from ANY)
		do
			if a = Void then
				Result := b = Void
			else
				Result := b /= Void and then a.is_equal (b)
			end
		ensure -- from ANY
			instance_free: class
			definition: Result = (a = Void and b = Void) or else ((a /= Void and b /= Void) and then a.is_equal (b))
		end

	frozen is_deep_equal alias "≡≡≡" (other: ARRAYED_QUEUE [G]): BOOLEAN
			-- Are Current and other attached to isomorphic object structures?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		external
			"built_in"
		ensure -- from ANY
			shallow_implies_deep: standard_is_equal (other) implies Result
			same_type: Result implies same_type (other)
			symmetric: Result implies other.is_deep_equal (Current)
		end

	is_equal (other: like Current): BOOLEAN
			-- Is other attached to an object considered
			-- equal to current object?
		require -- from ANY
			other_not_void: other /= Void
		local
			i, j: INTEGER_32
			nb, other_nb: INTEGER_32
			c: INTEGER_32
		do
			c := count
			if c = other.count and object_comparison = other.object_comparison then
				i := out_index - Lower
				j := other.out_index - Lower
				nb := area.capacity
				other_nb := other.area.capacity
				Result := True
				if object_comparison then
					from
					until
						c = 0 or not Result
					loop
						Result := area.item (i) ~ other.area.item (j)
						j := j + 1
						if j > other_nb then
							j := 0
						end
						i := i + 1
						if i = nb then
							i := 0
						end
						c := c - 1
					end
				else
					from
					until
						c = 0 or not Result
					loop
						Result := area.item (i) = other.area.item (j)
						j := j + 1
						if j > other_nb then
							j := 0
						end
						i := i + 1
						if i = nb then
							i := 0
						end
						c := c - 1
					end
				end
			end
		ensure -- from ANY
			symmetric: Result implies other ~ Current
			consistent: standard_is_equal (other) implies Result
		end

	frozen standard_equal (a: detachable ANY; b: like arg #1): BOOLEAN
			-- Are a and b either both void or attached to
			-- field-by-field identical objects of the same type?
			-- Always uses default object comparison criterion.
			-- (from ANY)
		do
			if a = Void then
				Result := b = Void
			else
				Result := b /= Void and then a.standard_is_equal (b)
			end
		ensure -- from ANY
			instance_free: class
			definition: Result = (a = Void and b = Void) or else ((a /= Void and b /= Void) and then a.standard_is_equal (b))
		end

	frozen standard_is_equal alias "≜" (other: ARRAYED_QUEUE [G]): 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
		external
			"built_in"
		ensure -- from ANY
			same_type: Result implies same_type (other)
			symmetric: Result implies other.standard_is_equal (Current)
		end
	
feature -- Status report

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

	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
		external
			"built_in"
		end

	empty: BOOLEAN
		obsolete "ELKS 2000: Use `is_empty' instead. [2017-05-31]"
			-- Is there no element?
			-- (from CONTAINER)
		do
			Result := is_empty
		end

	extendible: BOOLEAN
			-- May items be added? (Answer: yes.)
		do
			Result := True
		end

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

	is_empty: BOOLEAN
			-- Is the structure empty?
			-- Was declared in ARRAYED_QUEUE as synonym of off.
		require -- from  CONTAINER
			True
		do
			Result := count = 0
		end

	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)
		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 the structure empty?
			-- Was declared in ARRAYED_QUEUE as synonym of is_empty.
		do
			Result := count = 0
		end

	prunable: BOOLEAN
			-- May items be removed? (Answer: no.)
		do
			Result := False
		end

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

	replaceable: BOOLEAN
			-- Can current item be replaced?
			-- (from ACTIVE)
		do
			Result := True
		end

	resizable: BOOLEAN
			-- May capacity be changed? (Answer: yes.)
			-- (from RESIZABLE)
		do
			Result := True
		end

	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
		external
			"built_in"
		ensure -- from ANY
			definition: Result = (conforms_to (other) and other.conforms_to (Current))
		end

	writable: BOOLEAN
			-- Is there a current item that may be modified?
			-- (from DISPENSER)
		do
			Result := not is_empty
		end
	
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
		do
			object_comparison := True
		ensure -- from CONTAINER
				object_comparison
		end

	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
		do
			object_comparison := False
		ensure -- from CONTAINER
			reference_comparison: not object_comparison
		end
	
feature -- Element change

	append (s: SEQUENCE [G])
			-- Append a copy of s.
			-- (Synonym for fill)
			-- (from DISPENSER)
		require -- from DISPENSER
			s_not_void: s /= Void
			extendible: extendible
		do
			fill (s)
		end

	extend (v: G)
			-- Add v as newest item.
			-- Was declared in ARRAYED_QUEUE as synonym of put and force.
		require -- from COLLECTION
			extendible: extendible
		local
			l_capacity: like capacity
			l_count: like count
		do
			l_capacity := capacity
			l_count := count
			if l_count >= l_capacity then
				grow (l_capacity + additional_space)
			end;
			area.force (v, in_index - Lower)
			count := l_count + 1
		ensure -- from COLLECTION
			item_inserted: is_inserted (v)
		end

	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 COLLECTION)
		require -- from COLLECTION
			other_not_void: other /= Void
			extendible: 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)
			-- Add v as newest item.
			-- Was declared in ARRAYED_QUEUE as synonym of extend and put.
		require -- from DISPENSER
			extendible: extendible
		local
			l_capacity: like capacity
			l_count: like count
		do
			l_capacity := capacity
			l_count := count
			if l_count >= l_capacity then
				grow (l_capacity + additional_space)
			end;
			area.force (v, in_index - Lower)
			count := l_count + 1
		ensure -- from DISPENSER
			item_inserted: is_inserted (v)
		end

	put (v: G)
			-- Add v as newest item.
			-- Was declared in ARRAYED_QUEUE as synonym of extend and force.
		require -- from COLLECTION
			extendible: extendible
		local
			l_capacity: like capacity
			l_count: like count
		do
			l_capacity := capacity
			l_count := count
			if l_count >= l_capacity then
				grow (l_capacity + additional_space)
			end;
			area.force (v, in_index - Lower)
			count := l_count + 1
		ensure -- from COLLECTION
			item_inserted: is_inserted (v)
		end

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

	prune (v: G)
			-- Remove one occurrence of v if any.
			-- (Reference or object equality,
			-- based on object_comparison.)
		require -- from COLLECTION
			prunable: prunable
		do
		end

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

	remove
			-- Remove oldest item.
		require -- from ACTIVE
			prunable: prunable
			writable: writable
		require else
			writable: writable
		local
			l_removed_index: like out_index
		do
			l_removed_index := out_index
			out_index := l_removed_index \\ capacity + 1
			count := count - 1
			if count = 0 then
				wipe_out
			else
				area.put (newest_item, l_removed_index - Lower)
			end
		end

	wipe_out
			-- Remove all items.
		require -- from COLLECTION
			prunable: prunable
		require else
			prunable: True
		do
			area.wipe_out
			out_index := 1
			count := 0
		ensure -- from COLLECTION
			wiped_out: is_empty
		end
	
feature -- Resizing

	automatic_grow
			-- Change the capacity to accommodate at least
			-- Growth_percentage more items.
			-- (from RESIZABLE)
		require -- from RESIZABLE
			resizable: resizable
		do
			grow (capacity + additional_space)
		ensure -- from RESIZABLE
			increased_capacity: capacity >= old capacity + old additional_space
		end

	trim
			-- Decrease capacity to the minimum value.
			-- Apply to reduce allocated storage.
		require -- from  RESIZABLE
			True
		local
			i: like Lower
			j: like Lower
			n: like count
			m: like capacity
		do
			n := count
			m := capacity
			if n < m then
				i := out_index - Lower
				j := in_index - Lower
				if i < j then
					area.move_data (i, 0, n)
					out_index := Lower
				elseif n > 0 then
					area.move_data (i, j, m - i)
					out_index := j + Lower
				end
				area := area.aliased_resized_area (n)
			end
		ensure -- from RESIZABLE
			same_count: count = old count
			minimal_capacity: capacity = count
		ensure then
			same_items: linear_representation ~ old linear_representation
		end
	
feature -- Conversion

	linear_representation: ARRAYED_LIST [G]
			-- Representation as a linear structure
			-- (in the original insertion order)
		local
			i, j, nb: INTEGER_32
		do
			from
				i := out_index - Lower
				j := count
				nb := area.capacity
				create Result.make (j)
			until
				j = 0
			loop
				Result.extend (area.item (i))
				i := i + 1
				if i = nb then
					i := 0
				end
				j := j - 1
			end
		end
	
feature -- Duplication

	frozen clone (other: detachable ANY): like other
		obsolete "Use `twin' instead. [2017-05-31]"
			-- Void if other is void; otherwise new object
			-- equal to other
			--
			-- For non-void other, clone calls copy;
			-- to change copying/cloning semantics, redefine copy.
			-- (from ANY)
		do
			if other /= Void then
				Result := other.twin
			end
		ensure -- from ANY
			instance_free: class
			equal: Result ~ other
		end

	copy (other: like Current)
			-- Update current object using fields of object attached
			-- to other, so as to yield equal objects.
		require -- from ANY
			other_not_void: other /= Void
			type_identity: same_type (other)
		do
			if other /= Current then
				standard_copy (other)
				area := area.twin
			end
		ensure -- from ANY
			is_equal: Current ~ other
		end

	frozen deep_clone (other: detachable ANY): like other
		obsolete "Use `deep_twin' instead. [2017-05-31]"
			-- Void if other is void: otherwise, new object structure
			-- recursively duplicated from the one attached to other
			-- (from ANY)
		do
			if other /= Void then
				Result := other.deep_twin
			end
		ensure -- from ANY
			instance_free: class
			deep_equal: deep_equal (other, Result)
		end

	frozen deep_copy (other: ARRAYED_QUEUE [G])
			-- Effect equivalent to that of:
			--		copy (other . deep_twin)
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		do
			copy (other.deep_twin)
		ensure -- from ANY
			deep_equal: deep_equal (Current, other)
		end

	frozen deep_twin: ARRAYED_QUEUE [G]
			-- New object structure recursively duplicated from Current.
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			deep_twin_not_void: Result /= Void
			deep_equal: deep_equal (Current, Result)
		end

	frozen standard_clone (other: detachable ANY): like other
		obsolete "Use `standard_twin' instead. [2017-05-31]"
			-- Void if other is void; otherwise new object
			-- field-by-field identical to other.
			-- Always uses default copying semantics.
			-- (from ANY)
		do
			if other /= Void then
				Result := other.standard_twin
			end
		ensure -- from ANY
			instance_free: class
			equal: standard_equal (Result, other)
		end

	frozen standard_copy (other: ARRAYED_QUEUE [G])
			-- 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)
		external
			"built_in"
		ensure -- from ANY
			is_standard_equal: standard_is_equal (other)
		end

	frozen standard_twin: ARRAYED_QUEUE [G]
			-- New object field-by-field identical to other.
			-- Always uses default copying semantics.
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			standard_twin_not_void: Result /= Void
			equal: standard_equal (Result, Current)
		end

	frozen twin: ARRAYED_QUEUE [G]
			-- New object equal to Current
			-- twin calls copy; to change copying/twinning semantics, redefine copy.
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			twin_not_void: Result /= Void
			is_equal: Result ~ Current
		end
	
feature -- Basic operations

	frozen as_attached: attached ARRAYED_QUEUE [G]
		obsolete "Remove calls to this feature. [2017-05-31]"
			-- Attached version of Current.
			-- (Can be used during transitional period to convert
			-- non-void-safe classes to void-safe ones.)
			-- (from ANY)
		do
			Result := Current
		end

	frozen default: detachable ARRAYED_QUEUE [G]
			-- Default value of object's type
			-- (from ANY)
		do
		end

	frozen default_pointer: POINTER
			-- Default value of type POINTER
			-- (Avoid the need to write p.default for
			-- some p of type POINTER.)
			-- (from ANY)
		do
		ensure -- from ANY
			instance_free: class
		end

	default_rescue
			-- Process exception for routines with no Rescue clause.
			-- (Default: do nothing.)
			-- (from ANY)
		do
		end

	frozen do_nothing
			-- Execute a null action.
			-- (from ANY)
		do
		ensure -- from ANY
			instance_free: class
		end
	
feature {ARRAYED_QUEUE} -- Implementation

	in_index: INTEGER_32
			-- Position for next insertion
		local
			c: like capacity
		do
			c := capacity
			if c > 0 then
				Result := (out_index - Lower + count) \\ c + Lower
			else
				Result := out_index
			end
		end
	
feature -- Implementation

	grow (n: INTEGER_32)
			-- Ensure that capacity is at least i.
		require -- from RESIZABLE
			resizable: resizable
		local
			old_count, new_capacity: like capacity
			nb: INTEGER_32
		do
			new_capacity := area.capacity.max (n)
			if count = 0 or else in_index > out_index then
				area := area.aliased_resized_area (new_capacity)
			else
				old_count := area.count
				area := area.aliased_resized_area_with_default (newest_item, new_capacity)
				nb := old_count - out_index + 1;
				area.move_data (out_index - Lower, new_capacity - nb, nb)
				out_index := new_capacity - nb + 1
			end
		ensure -- from RESIZABLE
			new_capacity: capacity >= n
		end
	
feature {NONE} -- Implementation

	newest_item: G
			-- Most recently added item.
		local
			l_pos: INTEGER_32
		do
			l_pos := in_index - 1
			if l_pos = 0 then
				Result := area.item (area.upper)
			else
				Result := area.item (l_pos - Lower)
			end
		end

	upper: INTEGER_32
			-- Upper bound for accessing list items via indexes
		do
			Result := area.count
		end
	
feature -- Correction

	Mismatch_information: MISMATCH_INFORMATION
			-- Original attribute values of mismatched object
			-- (from MISMATCH_CORRECTOR)
		once
			create Result
		end
	
feature -- Iteration

	new_cursor: ARRAYED_QUEUE_ITERATION_CURSOR [G]
			-- Fresh cursor associated with current structure
		do
			create Result.make (Current)
		ensure -- from ITERABLE
			result_attached: Result /= Void
		end
	
feature -- Output

	Io: STD_FILES
			-- Handle to standard file setup
			-- (from ANY)
		once
			create Result;
			Result.set_output_default
		ensure -- from ANY
			instance_free: class
			io_not_void: Result /= Void
		end

	out: STRING_8
			-- New string containing terse printable representation
			-- of current object
			-- (from ANY)
		do
			Result := tagged_out
		ensure -- from ANY
			out_not_void: Result /= Void
		end

	print (o: detachable ANY)
			-- Write terse external representation of o
			-- on standard output.
			-- (from ANY)
		local
			s: READABLE_STRING_8
		do
			if attached o then
				s := o.out
				if attached {READABLE_STRING_32} s as s32 then
					Io.put_string_32 (s32)
				elseif attached {READABLE_STRING_8} s as s8 then
					Io.put_string (s8)
				else
					Io.put_string_32 (s.as_string_32)
				end
			end
		ensure -- from ANY
			instance_free: class
		end

	frozen tagged_out: STRING_8
			-- New string containing terse printable representation
			-- of current object
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			tagged_out_not_void: Result /= Void
		end
	
feature -- Platform

	Operating_environment: OPERATING_ENVIRONMENT
			-- Objects available from the operating system
			-- (from ANY)
		once
			create Result
		ensure -- from ANY
			instance_free: class
			operating_environment_not_void: Result /= Void
		end
	
feature -- Retrieval

	correct_mismatch
			-- Attempt to correct object mismatch using Mismatch_information.
		do
			if not Mismatch_information.has ("count") and then attached {SPECIAL [G]} Mismatch_information.item ("area") as a and then attached {INTEGER_32} Mismatch_information.item ("in_index") as i and then attached {INTEGER_32} Mismatch_information.item ("out_index") as o and then attached {BOOLEAN} Mismatch_information.item ("object_comparison") as c then
				area := a
				out_index := o
				if a.capacity = 0 then
					count := 0
				else
					count := (i - o + a.capacity) \\ a.capacity
				end
				object_comparison := c
			else
				Precursor
			end
		end
	
feature {NONE} -- Retrieval

	frozen internal_correct_mismatch
			-- Called from runtime to perform a proper dynamic dispatch on correct_mismatch
			-- from MISMATCH_CORRECTOR.
			-- (from ANY)
		local
			l_msg: STRING_32
			l_exc: EXCEPTIONS
		do
			if attached {MISMATCH_CORRECTOR} Current as l_corrector then
				l_corrector.correct_mismatch
			else
				create l_msg.make_from_string ("Mismatch: ".as_string_32)
				create l_exc;
				l_msg.append (generating_type.name_32);
				l_exc.raise_retrieval_exception (l_msg)
			end
		end
	
invariant
		-- 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 ANY
	reflexive_equality: standard_is_equal (Current)
	reflexive_conformance: conforms_to (Current)

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

		-- from RESIZABLE
	increase_by_at_least_one: Minimal_increase >= 1

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

note
	copyright: "Copyright (c) 1984-2018, Eiffel Software and others"
	license: "Eiffel Forum License v2 (see http://www.eiffel.com/licensing/forum.txt)"
	source: "[
		Eiffel Software
		5949 Hollister Ave., 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_QUEUE

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