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	description: "A sequence of actions to be performed on `call'"
	instructions: "[
		Use features inherited from LIST to add/remove actions.
		An action is a procedure of ANY class that takes EVENT_DATA.
		When `call' is called the actions in the list will be executed
		in order stating at `first'.
		An action may call `abort' which will cause `call' to stop executing
		actions in the sequence. (Until the next call to `call').
		Descendants may redefine `initialize' to arrange for `call' to
		be called by an event source.
		Use `block', `pause', `flush' and `resume' to change the behavior
		of `call'.
		eg.
		 birthday_data: TUPLE [INTEGER, STRING] -- (age, name)
		 birthday_actions: ACTIONS_SEQUENCE [like birthday_data]
		 create birthday_actions.make ("birthday", <<"age","name">>)
		 send_card (age: INTEGER, name, from: STRING) is ...
		 buy_gift (age: INTEGER, name, gift, from: STRING) is ...
		 birthday_actions.extend (~send_card (?, ?, "Sam")
		 birthday_actions.extend (~buy_gift (?, ?, "Wine", "Sam")
		 birthday_actions.call ([35, "Julia"])
		 causes call to: send_card (35, "Julia", "Sam")
		                 buy_gift (35, "Julia", "Wine", "Sam")
	]"
	status: "See notice at end of class"
	keywords: "event, action"
	date: "$Date: 2001-11-16 20:32:23 +0000 (Fri, 16 Nov 2001) $"
	revision: "$Revision: 51435 $"

class 
	ACTION_SEQUENCE [EVENT_DATA -> TUPLE create make end]

create 
	default_create,
	make

feature {NONE} -- Initialization

	default_create is
			-- Begin in Normal_state.
		do
			linked_list_make
			create is_aborted_stack.make
			create call_buffer.make
			state := normal_state
			create not_empty_actions.make
			create empty_actions.make
		end

	make is
		obsolete "use default_create"
		do
			default_create
		end
	
feature -- Initialization

	linked_list_make is
			-- Create an empty list.
			-- (from LINKED_LIST)
		do
			before := True
		ensure -- from LINKED_LIST
			is_before: before
		end
	
feature -- Access

	cursor: CURSOR is
			-- Current cursor position
			-- (from LINKED_LIST)
		do
			create {LINKED_LIST_CURSOR [PROCEDURE [ANY, EVENT_DATA]]} Result.make (active, after, before)
		end

	dummy_event_data: EVENT_DATA is
			-- Attribute of the generic type.
			-- Useful for introspection and use in like statements.
		do
			if dummy_event_data_internal = void then
				create dummy_event_data_internal.make
			end
			Result := dummy_event_data_internal
		end

	event_data_names: ARRAY [STRING] is
			-- Textual description of each event datum.
		do
			Result := deep_clone (event_data_names_internal)
		ensure
			equal_to_event_data_names_internal: deep_equal (Result, event_data_names_internal)
		end

	first: like item is
			-- Item at first position
			-- (from LINKED_LIST)
		require -- from CHAIN
			not_empty: not is_empty
		do
			Result := first_element.item
		end

	has (v: like item): BOOLEAN is
			-- Does chain include v?
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from CHAIN)
		local
			pos: CURSOR
		do
			pos := cursor
			Result := sequential_has (v)
			go_to (pos)
		ensure -- from CONTAINER
			not_found_in_empty: Result implies not is_empty
		end

	i_th (i: INTEGER): like item is
			-- Item at i-th position
			-- Was declared in CHAIN as synonym of @.
			-- (from CHAIN)
		require -- from TABLE
			valid_key: valid_index (k)
		local
			pos: CURSOR
		do
			pos := cursor
			go_i_th (i)
			Result := item
			go_to (pos)
		end

	index: INTEGER is
			-- Index of current position
			-- (from LINKED_LIST)
		local
			p: LINKED_LIST_CURSOR [PROCEDURE [ANY, EVENT_DATA]]
		do
			if after then
				Result := count + 1
			elseif not before then
				p ?= cursor;
				check
					p /= void
				end;
				from
					start
					Result := 1
				until
					p.active = active
				loop
					forth
					Result := Result + 1
				end;
				go_to (p)
			end
		end

	index_of (v: like item; i: INTEGER): INTEGER is
			-- 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
		local
			pos: CURSOR
		do
			pos := cursor
			Result := sequential_index_of (v, i)
			go_to (pos)
		ensure -- from LINEAR
			non_negative_result: Result >= 0
		end

	item: PROCEDURE [ANY, EVENT_DATA] is
			-- Current item
			-- (from LINKED_LIST)
		require -- from TRAVERSABLE
			not_off: not off
		require -- from ACTIVE
			readable: readable
		do
			Result := active.item
		end

	last: like item is
			-- Item at last position
			-- (from LINKED_LIST)
		require -- from CHAIN
			not_empty: not is_empty
		do
			Result := last_element.item
		end

	name: STRING is
			-- Textual description.
		do
			Result := clone (name_internal)
		ensure
			equal_to_name_internal: Result.is_equal (name_internal)
		end

	sequential_occurrences (v: PROCEDURE [ANY, EVENT_DATA]): INTEGER is
			-- Number of times v appears.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from LINEAR)
		do
			from
				start
				search (v)
			until
				exhausted
			loop
				Result := Result + 1
				forth
				search (v)
			end
		ensure -- from BAG
			non_negative_occurrences: Result >= 0
		end

	infix "@" (i: INTEGER): like item is
			-- Item at i-th position
			-- Was declared in CHAIN as synonym of i_th.
			-- (from CHAIN)
		require -- from TABLE
			valid_key: valid_index (k)
		local
			pos: CURSOR
		do
			pos := cursor
			go_i_th (i)
			Result := item
			go_to (pos)
		end
	
feature {NONE} -- Access

	sequential_has (v: like item): BOOLEAN is
			-- Does structure include an occurrence of v?
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from LINEAR)
		do
			start
			if not off then
				search (v)
			end
			Result := not exhausted
		ensure -- from CONTAINER
			not_found_in_empty: Result implies not is_empty
		end

	sequential_index_of (v: like item; i: INTEGER): INTEGER is
			-- Index of i-th occurrence of v.
			-- 0 if none.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from LINEAR)
		require -- from LINEAR
			positive_occurrences: i > 0
		local
			occur, pos: INTEGER
		do
			if object_comparison and v /= void then
				from
					start
					pos := 1
				until
					off or (occur = i)
				loop
					if item /= void and then v.is_equal (item) then
						occur := occur + 1
					end
					forth
					pos := pos + 1
				end
			else
				from
					start
					pos := 1
				until
					off or (occur = i)
				loop
					if item = v then
						occur := occur + 1
					end
					forth
					pos := pos + 1
				end
			end
			if occur = i then
				Result := pos - 1
			end
		ensure -- from LINEAR
			non_negative_result: Result >= 0
		end

	sequential_search (v: like item) is
			-- Move to first position (at or after current
			-- position) where item and v are equal.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- If no such position ensure that exhausted will be true.
			-- (from LINEAR)
		do
			if object_comparison and v /= void then
				from
				until
					exhausted or else (item /= void and then v.is_equal (item))
				loop
					forth
				end
			else
				from
				until
					exhausted or else v = item
				loop
					forth
				end
			end
		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
		end
	
feature -- Measurement

	count: INTEGER
			-- Number of items
			-- (from LINKED_LIST)

	index_set: INTEGER_INTERVAL is
			-- Range of acceptable indexes
			-- (from CHAIN)
		do
			create Result.make (1, count)
		ensure -- from INDEXABLE
			not_void: Result /= void
		ensure then -- from CHAIN
			count_definition: Result.count = count
		end

	occurrences (v: like item): INTEGER is
			-- Number of times v appears.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from CHAIN)
		local
			pos: CURSOR
		do
			pos := cursor
			Result := sequential_occurrences (v)
			go_to (pos)
		ensure -- from BAG
			non_negative_occurrences: Result >= 0
		end

	occurrences (v: like item): INTEGER is
			-- Number of times v appears.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from CHAIN)
		local
			pos: CURSOR
		do
			pos := cursor
			Result := sequential_occurrences (v)
			go_to (pos)
		ensure -- from BAG
			non_negative_occurrences: Result >= 0
		end
	
feature -- Comparison

	is_equal (other: like Current): BOOLEAN is
			-- Does other contain the same elements?
			-- (from LIST)
		require -- from ANY
			other_not_void: other /= void
		local
			c1, c2: CURSOR
		do
			if Current = other then
				Result := True
			else
				Result := (is_empty = other.is_empty) and (object_comparison = other.object_comparison)
				if Result and not is_empty then
					c1 ?= cursor
					c2 ?= other.cursor
					check
						cursors_exist: c1 /= void and c2 /= void
					end
					from
						start
						other.start
					until
						after or not Result
					loop
						if object_comparison then
							Result := equal (item, other.item)
						else
							Result := (item = other.item)
						end
						forth
						other.forth
					end
					go_to (c1)
					other.go_to (c2)
				elseif is_empty and other.is_empty and object_comparison = other.object_comparison then
					Result := True
				end
			end
		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
		end
	
feature -- Status report

	after: BOOLEAN
			-- Is there no valid cursor position to the right of cursor?
			-- (from LINKED_LIST)

	before: BOOLEAN
			-- Is there no valid cursor position to the left of cursor?
			-- (from LINKED_LIST)

	Blocked_state: INTEGER is 3

	call_is_underway: BOOLEAN is
			-- Is call currently being executed?
		do
			Result := not is_aborted_stack.is_empty
		ensure
			Result = not is_aborted_stack.is_empty
		end

	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

	exhausted: BOOLEAN is
			-- Has structure been completely explored?
			-- (from LINEAR)
		do
			Result := off
		ensure -- from LINEAR
			exhausted_when_off: off implies Result
		end

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

	Full: BOOLEAN is False
			-- Is structured filled to capacity? (Answer: no.)
			-- (from LINKED_LIST)

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

	is_inserted (v: PROCEDURE [ANY, EVENT_DATA]): BOOLEAN is
			-- Has v been inserted at the end by the most recent put or
			-- extend?
			-- (from LINKED_LIST)
		do
			check
				put_constraint: (v /= last_element.item) implies not off
			end
			Result := (v = last_element.item) or else (v = item)
		end

	isfirst: BOOLEAN is
			-- Is cursor at first position?
			-- (from LINKED_LIST)
		do
			Result := not after and not before and (active = first_element)
		ensure -- from CHAIN
			valid_position: Result implies not is_empty
		end

	islast: BOOLEAN is
			-- Is cursor at last position?
			-- (from LINKED_LIST)
		do
			Result := not after and not before and (active /= void) and then (active.right = void)
		ensure -- from CHAIN
			valid_position: Result implies not is_empty
		end

	Normal_state: INTEGER is 1

	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?
			-- (from LINKED_LIST)
		do
			Result := after or before
		end

	Paused_state: INTEGER is 2

	prunable: BOOLEAN is
			-- May items be removed? (Answer: yes.)
			-- (from DYNAMIC_CHAIN)
		do
			Result := True
		end

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

	state: INTEGER
			-- One of Normal_state Paused_state or Blocked_state

	valid_cursor (p: CURSOR): BOOLEAN is
			-- Can the cursor be moved to position p?
			-- (from LINKED_LIST)
		local
			ll_c: LINKED_LIST_CURSOR [PROCEDURE [ANY, EVENT_DATA]]
			temp, sought: like first_element
		do
			ll_c ?= p
			if ll_c /= void then
				from
					temp := first_element
					sought := ll_c.active
					Result := ll_c.after or else ll_c.before
				until
					Result or else temp = void
				loop
					Result := (temp = sought)
					temp := temp.right
				end
			end
		end

	valid_cursor_index (i: INTEGER): BOOLEAN is
			-- Is i correctly bounded for cursor movement?
			-- (from CHAIN)
		do
			Result := (i >= 0) and (i <= count + 1)
		ensure -- from CHAIN
			valid_cursor_index_definition: Result = ((i >= 0) and (i <= count + 1))
		end

	valid_index (i: INTEGER): BOOLEAN is
			-- Is i within allowable bounds?
			-- (from CHAIN)
		do
			Result := (i >= 1) and (i <= count)
		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))
		end

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

	abort is
			-- Abort the current call.
			-- (The current item.call will be completed.)
		require
			call_is_underway: call_is_underway
		do
			is_aborted_stack.replace (True)
		ensure
			is_aborted_set: is_aborted_stack.item
		end

	block is
			-- Ignore subsequent calls.
		do
			state := blocked_state
		ensure
			blocked_state: state = blocked_state
		end

	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

	flush is
			-- Discard any buffered calls.
		do
			call_buffer.wipe_out
		ensure
			call_buffer_empty: call_buffer.is_empty
		end

	pause is
			-- Buffer subsequent calls for later execution.
			-- If is_blocked calls will simply be ignored.
		do
			state := paused_state
		ensure
			paused_state: state = paused_state
		end

	resume is
			-- Used after block or pause to resume normal call
			-- execution.  Executes any buffered calls.
		do
			state := normal_state
			from
			until
				call_buffer.is_empty
			loop
				call (call_buffer.item)
				call_buffer.remove
			end
		ensure
			normal_state: state = normal_state
		end
	
feature -- Cursor movement

	back is
			-- Move to previous item.
			-- (from LINKED_LIST)
		require -- from BILINEAR
			not_before: not before
		do
			if is_empty then
				before := True
				after := False
			elseif after then
				after := False
			elseif isfirst then
				before := True
			else
				active := previous
			end
		end

	finish is
			-- Move cursor to last position.
			-- (Go before if empty)
			-- (from LINKED_LIST)
		local
			p: like first_element
		do
			if not is_empty then
				from
					p := active
				until
					p.right = void
				loop
					p := p.right
				end
				active := p
				after := False
				before := False
			else
				before := True
				after := False
			end
		ensure then -- from CHAIN
			at_last: not is_empty implies islast
		ensure then -- from LINKED_LIST
			empty_convention: is_empty implies before
		end

	forth is
			-- Move cursor to next position.
			-- (from LINKED_LIST)
		require -- from LINEAR
			not_after: not after
		local
			old_active: like first_element
		do
			if before then
				before := False
				if is_empty then
					after := True
				end
			else
				old_active := active
				active := active.right
				if active = void then
					active := old_active
					after := True
				end
			end
		ensure then -- from LIST
			moved_forth: index = old index + 1
		end

	go_i_th (i: INTEGER) is
			-- Move cursor to i-th position.
			-- (from LINKED_LIST)
		require -- from CHAIN
			valid_cursor_index: valid_cursor_index (i)
		do
			if i = 0 then
				before := True
				after := False
				active := first_element
			elseif i = count + 1 then
				before := False;
				after := True;
				active := last_element
			else
				move (i - index)
			end
		ensure -- from CHAIN
			position_expected: index = i
		end

	go_to (p: CURSOR) is
			-- Move cursor to position p.
			-- (from LINKED_LIST)
		require -- from CURSOR_STRUCTURE
			cursor_position_valid: valid_cursor (p)
		local
			ll_c: LINKED_LIST_CURSOR [PROCEDURE [ANY, EVENT_DATA]]
		do
			ll_c ?= p
			check
				ll_c /= void
			end
			after := ll_c.after
			before := ll_c.before
			if before then
				active := first_element
			elseif after then
				active := last_element
			else
				active := ll_c.active
			end
		end

	move (i: INTEGER) is
			-- Move cursor i positions. The cursor
			-- may end up off if the offset is too big.
			-- (from LINKED_LIST)
		local
			counter, new_index: INTEGER
			p: like first_element
		do
			if i > 0 then
				if before then
					before := False
					counter := 1
				end
				from
					p := active
				until
					(counter = i) or else (p = void)
				loop
					active := p
					p := p.right
					counter := counter + 1
				end
				if p = void then
					after := True
				else
					active := p
				end
			elseif i < 0 then
				new_index := index + i;
				before := True;
				after := False;
				active := first_element;
				if (new_index > 0) then
					move (new_index)
				end
			end
		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)
		ensure then -- from LINKED_LIST
			moved_if_inbounds: ((old index + i) >= 0 and (old index + i) <= (count + 1)) implies index = (old index + i)
			before_set: (old index + i) <= 0 implies before
			after_set: (old index + i) >= (count + 1) implies after
		end

	search (v: like item) is
			-- 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.)
			-- (from BILINEAR)
		do
			if before and not is_empty then
				forth
			end
			sequential_search (v)
		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
		end

	start is
			-- Move cursor to first position.
			-- (from LINKED_LIST)
		do
			if first_element /= void then
				active := first_element
				after := False
			else
				after := True
			end
			before := False
		ensure then -- from CHAIN
			at_first: not is_empty implies isfirst
		ensure then -- from LINKED_LIST
			empty_convention: is_empty implies after
		end
	
feature -- Element change

	append (s: SEQUENCE [PROCEDURE [ANY, EVENT_DATA]]) is
			-- Append a copy of s.
			-- (from SEQUENCE)
		require -- from SEQUENCE
			argument_not_void: s /= void
		local
			l: like s
		do
			if s = Current then
				l := deep_clone (s)
			else
				l := s
			end
			from
				l.start
			until
				l.exhausted
			loop
				extend (l.item)
				l.forth
			end
		ensure -- from SEQUENCE
			new_count: count >= old count
		end

	extend (v: like item) is
			-- Add v to end.
			-- Do not move cursor.
			-- (from LINKED_LIST)
		require -- from COLLECTION
			extendible: extendible
		local
			p: like first_element
		do
			p := new_cell (v)
			if is_empty then
				first_element := p
				active := p
			else
				last_element.put_right (p)
				if after then
					active := p
				end
			end
			count := count + 1
		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 [PROCEDURE [ANY, EVENT_DATA]]) 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 [PROCEDURE [ANY, EVENT_DATA]]
		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: like item) is
			-- Add v to end.
			-- (from SEQUENCE)
		require -- from SEQUENCE
			extendible: extendible
		do
			extend (v)
		ensure then -- from SEQUENCE
			new_count: count = old count + 1
			item_inserted: has (v)
		end

	put (v: like item) is
			-- Replace current item by v.
			-- (Synonym for replace)
			-- (from CHAIN)
		require -- from COLLECTION
			extendible: extendible
		do
			replace (v)
		ensure -- from COLLECTION
			item_inserted: is_inserted (v)
		ensure then -- from CHAIN
			same_count: count = old count
		end

	put_front (v: like item) is
			-- Add v to beginning.
			-- Do not move cursor.
			-- (from LINKED_LIST)
		local
			p: like first_element
		do
			p := new_cell (v)
			p.put_right (first_element)
			first_element := p
			if before or is_empty then
				active := p
			end
			count := count + 1
		ensure -- from DYNAMIC_CHAIN
			new_count: count = old count + 1
			item_inserted: first = v
		end

	put_i_th (v: like item; i: INTEGER) is
			-- Put v at i-th position.
			-- (from CHAIN)
		require -- from TABLE
			valid_key: valid_index (k)
		local
			pos: CURSOR
		do
			pos := cursor
			go_i_th (i)
			replace (v)
			go_to (pos)
		ensure then -- from INDEXABLE
			insertion_done: i_th (k) = v
		end

	put_left (v: like item) is
			-- Add v to the left of cursor position.
			-- Do not move cursor.
			-- (from LINKED_LIST)
		require -- from DYNAMIC_CHAIN
			extendible: extendible
			not_before: not before
		local
			p: like first_element
		do
			if is_empty then
				put_front (v)
			elseif after then
				back;
				put_right (v);
				move (2)
			else
				p := new_cell (active.item)
				p.put_right (active.right)
				active.put (v)
				active.put_right (p)
				active := p
				count := count + 1
			end
		ensure -- from DYNAMIC_CHAIN
			new_count: count = old count + 1
			new_index: index = old index + 1
		ensure then -- from LINKED_LIST
			previous_exists: previous /= void
			item_inserted: previous.item = v
		end

	put_right (v: like item) is
			-- Add v to the right of cursor position.
			-- Do not move cursor.
			-- (from LINKED_LIST)
		require -- from DYNAMIC_CHAIN
			extendible: extendible
			not_after: not after
		local
			p: like first_element
		do
			p := new_cell (v)
			check
				is_empty implies before
			end
			if before then
				p.put_right (first_element)
				first_element := p
				active := p
			else
				p.put_right (active.right)
				active.put_right (p)
			end
			count := count + 1
		ensure -- from DYNAMIC_CHAIN
			new_count: count = old count + 1
			same_index: index = old index
		ensure then -- from LINKED_LIST
			next_exists: next /= void
			item_inserted: not old before implies next.item = v
			item_inserted_before: old before implies active.item = v
		end

	replace (v: like item) is
			-- Replace current item by v.
			-- (from LINKED_LIST)
		require -- from ACTIVE
			writable: writable
		do
			active.put (v)
		ensure -- from ACTIVE
			item_replaced: item = v
		end
	
feature {NONE} -- Element change

	sequence_put (v: like item) is
			-- Add v to end.
			-- (from SEQUENCE)
		require -- from COLLECTION
			extendible: extendible
		do
			extend (v)
		ensure -- from COLLECTION
			item_inserted: is_inserted (v)
		ensure then -- from SEQUENCE
			new_count: count = old count + 1
		end
	
feature -- Removal

	prune (v: like item) is
			-- Remove first occurrence of v, if any,
			-- after cursor position.
			-- If found, move cursor to right neighbor;
			-- if not, make structure exhausted.
			-- (from DYNAMIC_CHAIN)
		require -- from COLLECTION
			prunable: prunable
		do
			search (v)
			if not exhausted then
				remove
			end
		end

	prune_all (v: like item) is
			-- Remove all occurrences of v.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- Leave structure exhausted.
			-- (from DYNAMIC_CHAIN)
		require -- from COLLECTION
			prunable
		do
			from
				start
				search (v)
			until
				exhausted
			loop
				remove
				search (v)
			end
		ensure -- from COLLECTION
			no_more_occurrences: not has (v)
		ensure then -- from DYNAMIC_CHAIN
			is_exhausted: exhausted
		end

	remove is
			-- Remove current item.
			-- Move cursor to right neighbor
			-- (or after if no right neighbor).
			-- (from LINKED_LIST)
		require -- from ACTIVE
			prunable: prunable
			writable: writable
		local
			removed, succ: like first_element
		do
			removed := active
			if isfirst then
				first_element := first_element.right
				active.forget_right
				active := first_element
				if count = 1 then
					check
						no_active: active = void
					end
					after := True
				end
			elseif islast then
				active := previous;
				if active /= void then
					active.forget_right
				end;
				after := True
			else
				succ := active.right
				previous.put_right (succ)
				active.forget_right
				active := succ
			end
			count := count - 1
			cleanup_after_remove (removed)
		ensure then -- from DYNAMIC_LIST
			after_when_empty: is_empty implies after
		end

	remove_left is
			-- Remove item to the left of cursor position.
			-- Do not move cursor.
			-- (from LINKED_LIST)
		require -- from DYNAMIC_CHAIN
			left_exists: index > 1
		require else -- from DYNAMIC_LIST
			not_before: not before
		do
			move (- 2)
			remove_right
			forth
		ensure -- from DYNAMIC_CHAIN
			new_count: count = old count - 1
			new_index: index = old index - 1
		end

	remove_right is
			-- Remove item to the right of cursor position.
			-- Do not move cursor.
			-- (from LINKED_LIST)
		require -- from DYNAMIC_CHAIN
			right_exists: index < count
		local
			removed, succ: like first_element
		do
			if before then
				removed := first_element
				first_element := first_element.right
				active.forget_right
				active := first_element
			else
				succ := active.right
				removed := succ
				active.put_right (succ.right)
				succ.forget_right
			end
			count := count - 1
			cleanup_after_remove (removed)
		ensure -- from DYNAMIC_CHAIN
			new_count: count = old count - 1
			same_index: index = old index
		end
	
feature {NONE} -- Removal

	chain_wipe_out is
			-- Remove all items.
			-- (from DYNAMIC_CHAIN)
		require -- from COLLECTION
			prunable
		do
			from
				start
			until
				is_empty
			loop
				remove
			end
		ensure -- from COLLECTION
			wiped_out: is_empty
		end
	
feature -- Transformation

	swap (i: INTEGER) is
			-- Exchange item at i-th position with item
			-- at cursor position.
			-- (from CHAIN)
		require -- from CHAIN
			not_off: not off
			valid_index: valid_index (i)
		local
			old_item, new_item: like item
			pos: CURSOR
		do
			pos := cursor
			old_item := item
			go_i_th (i)
			new_item := item
			replace (old_item)
			go_to (pos)
			replace (new_item)
		ensure -- from CHAIN
			swapped_to_item: item = old i_th (i)
			swapped_from_item: i_th (i) = old item
		end
	
feature -- Conversion

	linear_representation: LINEAR [PROCEDURE [ANY, EVENT_DATA]] is
			-- Representation as a linear structure
			-- (from LINEAR)
		do
			Result := Current
		end
	
feature -- Duplication

	copy (other: like Current) is
			-- Update current object using fields of object attached
			-- to other, so as to yield equal objects.
			-- (from LINKED_LIST)
		require -- from ANY
			other_not_void: other /= void
			type_identity: same_type (other)
		local
			cur: LINKED_LIST_CURSOR [PROCEDURE [ANY, EVENT_DATA]]
			new_list: like Current
			obj_comparison: BOOLEAN
		do
			obj_comparison := other.object_comparison
			if not other.is_empty then
				cur ?= other.cursor
				create new_list.linked_list_make
				from
					other.start
				until
					other.off
				loop
					new_list.extend (other.item)
					other.forth
				end
				other.go_to (cur)
			else
				new_list := other
			end
			standard_copy (new_list)
			object_comparison := obj_comparison
		ensure -- from ANY
			is_equal: is_equal (other)
		end

	duplicate (n: INTEGER): like Current is
			-- Copy of sub-chain beginning at current position
			-- and having min (n, from_here) items,
			-- where from_here is the number of items
			-- at or to the right of current position.
			-- (from DYNAMIC_CHAIN)
		require -- from CHAIN
			not_off_unless_after: off implies after
			valid_subchain: n >= 0
		local
			pos: CURSOR
			counter: INTEGER
		do
			from
				Result := new_chain
				if object_comparison then
					Result.compare_objects
				end
				pos := cursor
			until
				(counter = n) or else exhausted
			loop
				Result.extend (item)
				forth
				counter := counter + 1
			end
			go_to (pos)
		end
	
feature -- Basic operations

	call (event_data: EVENT_DATA) is
			-- Call each procedure in order unless is_blocked.
			-- If is_paused delay execution until resume.
			-- Stop at current point in list on abort.
		local
			snapshot: LINKED_LIST [PROCEDURE [ANY, EVENT_DATA]]
		do
			create snapshot.make
			snapshot.fill (Current)
			if kamikazes /= void then
				call_action_list (kamikazes)
				kamikazes := void
			end
			inspect state
			when normal_state then 
				from
					is_aborted_stack.extend (False)
					snapshot.start
				variant
					snapshot.count + 1 - snapshot.index
				until
					snapshot.after or is_aborted_stack.item
				loop
					snapshot.item.call (event_data)
					snapshot.forth
				end;
				is_aborted_stack.remove
			when paused_state then 
				call_buffer.extend (event_data)
			when blocked_state then 
			end
		ensure
			is_aborted_stack_unchanged: old is_aborted_stack.is_equal (is_aborted_stack)
		end
	
feature {NONE} -- Inapplicable

	bag_put (v: PROCEDURE [ANY, EVENT_DATA]) is
			-- (from TABLE)
		require -- from COLLECTION
			extendible: extendible
		do
		ensure -- from COLLECTION
			item_inserted: is_inserted (v)
		end
	
feature {LINKED_LIST} -- Implementation

	cleanup_after_remove (v: like first_element) is
			-- Clean-up a just removed cell.
		require -- from LINKED_LIST
			non_void_cell: v /= void
		do
			Precursor  (v)
			if count = 0 then
				call_action_list (empty_actions)
			end
		end

	new_cell (v: like item): like first_element is
			-- Create new cell with v.
		do
			if count = 0 then
				Result := Precursor  (v)
				call_action_list (not_empty_actions)
			else
				Result := Precursor  (v)
			end
		ensure -- from LINKED_LIST
			result_exists: Result /= void
		end
	
feature {NONE} -- Implementation

	call_action_list (actions: LINKED_LIST [PROCEDURE [ANY, TUPLE]]) is
			-- Call each action in actions.
		require
			actions_not_void: actions /= void
		local
			snapshot: like actions
		do
			create snapshot.make
			snapshot.fill (actions)
			from
				snapshot.start
			until
				snapshot.after
			loop
				snapshot.item.call ([])
				snapshot.forth
			end
		end

	call_buffer: LINKED_QUEUE [EVENT_DATA]
			-- Holds calls made while is_paused
			-- to be executed on resume.

	dummy_event_data_internal: EVENT_DATA
			-- See dummy_event_data.

	event_data_names_internal: ARRAY [STRING]
			-- See event_data_names.

	is_aborted_stack: LINKED_STACK [BOOLEAN]
			-- item holds abort status of
			-- innermost of possibly recursive calls.

	kamikazes: LINKED_LIST [PROCEDURE [ANY, TUPLE]]
			-- Used by prune_when_called.

	name_internal: STRING
			-- See name.

	source_connection_agent: PROCEDURE [ANY, TUPLE]
	
feature {LINKED_LIST} -- Implementation

	active: like first_element
			-- Element at cursor position
			-- (from LINKED_LIST)

	first_element: LINKABLE [PROCEDURE [ANY, EVENT_DATA]]
			-- Head of list
			-- (from LINKED_LIST)

	last_element: like first_element is
			-- Tail of list
			-- (from LINKED_LIST)
		local
			p: like first_element
		do
			if not is_empty then
				from
					Result := active
					p := active.right
				until
					p = void
				loop
					Result := p
					p := p.right
				end
			end
		end

	new_chain: like Current is
			-- A newly created instance of the same type.
			-- This feature may be redefined in descendants so as to
			-- produce an adequately allocated and initialized object.
			-- (from LINKED_LIST)
		do
			create Result.linked_list_make
		ensure -- from DYNAMIC_CHAIN
			result_exists: Result /= void
		end

	next: like first_element is
			-- Element right of cursor
			-- (from LINKED_LIST)
		do
			if before then
				Result := active
			elseif active /= void then
				Result := active.right
			end
		end

	previous: like first_element is
			-- Element left of cursor
			-- (from LINKED_LIST)
		local
			p: like first_element
		do
			if after then
				Result := active
			elseif not (isfirst or before) then
				from
					p := first_element
				until
					p.right = active
				loop
					p := p.right
				end;
				Result := p
			end
		end
	
feature -- Element Change

	merge_left (other: like Current) is
			-- Merge other into current structure after cursor
			-- position. Do not move cursor. Empty other
		require -- from DYNAMIC_CHAIN
			extendible: extendible
			not_before: not before
			other_exists: other /= void
		do
			if count = 0 then
				Precursor  (other)
				if count > 0 then
					call_action_list (not_empty_actions)
				end
			else
				Precursor  (other)
			end
		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
		ensure then -- from DYNAMIC_LIST
			other_empty: other.is_empty
		end

	merge_right (other: like Current) is
			-- Merge other into current structure before cursor
			-- position. Do not move cursor. Empty other
		require -- from DYNAMIC_CHAIN
			extendible: extendible
			not_after: not after
			other_exists: other /= void
		do
			if count = 0 then
				Precursor  (other)
				if count > 0 then
					call_action_list (not_empty_actions)
				end
			else
				Precursor  (other)
			end
		ensure -- from DYNAMIC_CHAIN
			new_count: count = old count + old other.count
			same_index: index = old index
			other_is_empty: other.is_empty
		ensure then -- from DYNAMIC_LIST
			other_empty: other.is_empty
		end

	prune_when_called (an_action: like item) is
			-- Remove an_action after the next time it is called.
		require
			has (an_action)
		do
			if kamikazes = void then
				create kamikazes.make
			end
			kamikazes.extend (agent prune_all (an_action))
		end

	set_source_connection_agent (a_source_connection_agent: PROCEDURE [ANY, TUPLE]) is
		obsolete "use not_empty_actions"
			-- Set a_source_connection_agent that will connect sequence to an
			-- actual event source. The agent will be called when the first action is
			-- added to the sequence. If there are already actions in the
			-- sequence the agent is called immediately.
		do
			not_empty_actions.extend (a_source_connection_agent)
			if not is_empty then
				a_source_connection_agent.call ([])
			end
		end

	wipe_out is
			-- Remove all items.
		require -- from COLLECTION
			prunable
		do
			Precursor
			call_action_list (empty_actions)
		ensure -- from COLLECTION
			wiped_out: is_empty
		ensure then -- from DYNAMIC_LIST
			is_before: before
		end
	
feature -- Event handling

	empty_actions: LINKED_LIST [PROCEDURE [ANY, TUPLE]]
			-- Actions to be performed on transition from not is_empty to is_empty.

	not_empty_actions: LINKED_LIST [PROCEDURE [ANY, TUPLE]]
			-- Actions to be performed on transition from is_empty to not is_empty.
	
feature -- Iteration

	do_all (action: PROCEDURE [ANY, TUPLE [PROCEDURE [ANY, EVENT_DATA]]]) is
			-- 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
		local
			t: TUPLE [PROCEDURE [ANY, EVENT_DATA]]
		do
			create t.make
			from
				start
			until
				after
			loop
				t.put (item, 1)
				action.call (t)
				forth
			end
		end

	do_if (action: PROCEDURE [ANY, TUPLE [PROCEDURE [ANY, EVENT_DATA]]]; test: FUNCTION [ANY, TUPLE [PROCEDURE [ANY, EVENT_DATA]], BOOLEAN]) is
			-- 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
		local
			t: TUPLE [PROCEDURE [ANY, EVENT_DATA]]
		do
			create t.make
			from
				start
			until
				after
			loop
				t.put (item, 1)
				if test.item (t) then
					action.call (t)
				end
				forth
			end
		end

	for_all (test: FUNCTION [ANY, TUPLE [PROCEDURE [ANY, EVENT_DATA]], BOOLEAN]): BOOLEAN is
			-- Is test true for all items?
			-- (from LINEAR)
		require -- from TRAVERSABLE
			test_exits: test /= void
		local
			cs: CURSOR_STRUCTURE [PROCEDURE [ANY, EVENT_DATA]]
			c: CURSOR
			t: TUPLE [PROCEDURE [ANY, EVENT_DATA]]
		do
			create t.make
			cs ?= Current
			if cs /= void then
				c := cs.cursor
			end
			from
				start
				Result := True
			until
				after or not Result
			loop
				t.put (item, 1)
				Result := test.item (t)
				forth
			end
			if cs /= void then
				cs.go_to (c)
			end
		end

	there_exists (test: FUNCTION [ANY, TUPLE [PROCEDURE [ANY, EVENT_DATA]], BOOLEAN]): BOOLEAN is
			-- Is test true for at least one item?
			-- (from LINEAR)
		require -- from TRAVERSABLE
			test_exits: test /= void
		local
			cs: CURSOR_STRUCTURE [PROCEDURE [ANY, EVENT_DATA]]
			c: CURSOR
			t: TUPLE [PROCEDURE [ANY, EVENT_DATA]]
		do
			create t.make
			cs ?= Current
			if cs /= void then
				c := cs.cursor
			end
			from
				start
			until
				after or Result
			loop
				t.put (item, 1)
				Result := test.item (t)
				forth
			end
			if cs /= void then
				cs.go_to (c)
			end
		end
	
invariant

	is_aborted_stack_not_void: is_aborted_stack /= void
	call_buffer_not_void: call_buffer /= void
	not_has_void: not has (void)
	valid_state: state = normal_state or state = paused_state or state = blocked_state
	call_buffer_consistent: state = normal_state implies call_buffer.is_empty
	not_empty_actions_not_void: not_empty_actions /= void
	empty_actions_not_void: empty_actions /= void
		-- from ANY
	reflexive_equality: standard_is_equal (Current)
	reflexive_conformance: conforms_to (Current)
		-- from LINKED_LIST
	prunable: prunable
	empty_constraint: is_empty implies ((first_element = void) and (active = void))
	not_void_unless_empty: (active = void) implies is_empty
	before_constraint: before implies (active = first_element)
	after_constraint: after implies (active = last_element)
		-- 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 INDEXABLE
	index_set_not_void: index_set /= void
		-- 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 FINITE
	empty_definition: is_empty = (count = 0)
	non_negative_count: count >= 0
		-- 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 ACTION_SEQUENCE


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