note
	description: "Objects that traverse object graphs starting at the root object in a depth first manner."
	library: "Free implementation of ELKS library"
	legal: "See notice at end of class."
	status: "See notice at end of class."
	author: "Stephanie Balzer"
	date: "$Date: 2013-03-27 07:34:50 +0000 (Wed, 27 Mar 2013) $"
	revision: "$Revision: 92359 $"

class 
	OBJECT_GRAPH_DEPTH_FIRST_TRAVERSABLE

create 
	default_create

feature {NONE} -- Initialization

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

	generating_type: TYPE [detachable OBJECT_GRAPH_DEPTH_FIRST_TRAVERSABLE]
			-- 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

	object_action: detachable PROCEDURE [separate ANY]
			-- Action called on every object in object graph
			-- (from OBJECT_GRAPH_TRAVERSABLE)

	on_processing_object_action: detachable PROCEDURE [REFLECTED_OBJECT]
			-- Action called on every object in the object graph.
			-- Note: The argument is reused later for a different object. Do not alias it.
			-- (from OBJECT_GRAPH_TRAVERSABLE)

	on_processing_reference_action: detachable PROCEDURE [REFLECTED_OBJECT, REFLECTED_OBJECT]
			-- Action called on every reference in the object graph.
			-- Note: The arguments are reused later for different objects. Do not alias them.
			-- (from OBJECT_GRAPH_TRAVERSABLE)

	root_object: detachable ANY
			-- Starting point of graph traversing
			-- (from OBJECT_GRAPH_TRAVERSABLE)

	visited_objects: detachable ARRAYED_LIST [separate ANY]
			-- List referencing objects of object graph that have been visited in traverse.
			-- (from OBJECT_GRAPH_TRAVERSABLE)

	visited_types: detachable HASH_TABLE [INTEGER_32, INTEGER_32]
			-- List of all types encountered during traversal
			-- (from OBJECT_GRAPH_TRAVERSABLE)
	
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: OBJECT_GRAPH_DEPTH_FIRST_TRAVERSABLE): 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: OBJECT_GRAPH_DEPTH_FIRST_TRAVERSABLE): BOOLEAN
			-- Is other attached to an object considered
			-- equal to current object?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		external
			"built_in"
		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: OBJECT_GRAPH_DEPTH_FIRST_TRAVERSABLE): 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

	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

	has_failed: BOOLEAN
			-- Was the last traversal successful?
			-- (from OBJECT_GRAPH_TRAVERSABLE)

	has_reference_with_copy_semantics: BOOLEAN
			-- Does the traversed graph of objects contain reference with copy semantics?
			-- (from OBJECT_GRAPH_TRAVERSABLE)

	is_exception_on_copy_suppressed: BOOLEAN
			-- Do we suppress an exception when object_action is called on a copied object?
			-- A copy happens when encountering tuples containing copy-semantics references
			-- or with SPECIAL[XX], where XX is a user-defined expanded type.
			-- (from OBJECT_GRAPH_TRAVERSABLE)

	is_exception_propagated: BOOLEAN
			-- Does the algorithm propagate any exceptions to the user?
			-- (from OBJECT_GRAPH_TRAVERSABLE)

	is_object_action_set: BOOLEAN
			-- Is procedure to call on every object set?
			-- (from OBJECT_GRAPH_TRAVERSABLE)
		do
			Result := object_action /= Void
		end

	is_root_object_set: BOOLEAN
			-- Is starting point of graph traversing set?
			-- (from OBJECT_GRAPH_TRAVERSABLE)
		do
			Result := root_object /= Void
		end

	is_skip_copy_semantics_reference: BOOLEAN
			-- Do we skip copy semantics reference from visited_objects during traversal?
			-- (from OBJECT_GRAPH_TRAVERSABLE)

	is_skip_transient: BOOLEAN
			-- Do we skip transient attribute during traversal?
			-- (from OBJECT_GRAPH_TRAVERSABLE)

	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
	
feature -- Element change

	set_is_exception_on_copy_suppressed (v: like is_exception_on_copy_suppressed)
			-- Set set_is_exception_on_copy_suppressed with v.
			-- (from OBJECT_GRAPH_TRAVERSABLE)
		do
			is_exception_on_copy_suppressed := v
		ensure -- from OBJECT_GRAPH_TRAVERSABLE
			is_exception_on_copy_suppressed_set: is_exception_on_copy_suppressed = v
		end

	set_is_exception_propagated (v: like is_exception_propagated)
			-- Set is_exception_propagated with v.
			-- (from OBJECT_GRAPH_TRAVERSABLE)
		do
			is_exception_propagated := v
		ensure -- from OBJECT_GRAPH_TRAVERSABLE
			is_exception_propagated_set: is_exception_propagated = v
		end

	set_is_skip_copy_semantics_reference (v: like is_skip_copy_semantics_reference)
			-- Set is_skip_copy_semantics_reference with v.
			-- (from OBJECT_GRAPH_TRAVERSABLE)
		do
			is_skip_copy_semantics_reference := v
		ensure -- from OBJECT_GRAPH_TRAVERSABLE
			is_skip_copy_semantics_reference_set: is_skip_copy_semantics_reference = v
		end

	set_is_skip_transient (v: like is_skip_transient)
			-- Set is_skip_transient with v.
			-- (from OBJECT_GRAPH_TRAVERSABLE)
		do
			is_skip_transient := v
		ensure -- from OBJECT_GRAPH_TRAVERSABLE
			is_skip_transient_set: is_skip_transient = v
		end

	set_object_action (an_object_action: like object_action)
		obsolete "Use set_on_processing_object_action to read and manipulate objects via REFLECTED_OBJECT. [2017-05-31]"
			-- Set object_action with an_object_action.
			-- (from OBJECT_GRAPH_TRAVERSABLE)
		require -- from OBJECT_GRAPH_TRAVERSABLE
			an_object_action_not_void: an_object_action /= Void
		do
			object_action := an_object_action
		ensure -- from OBJECT_GRAPH_TRAVERSABLE
			an_object_action_set: object_action = an_object_action and is_object_action_set
		end

	set_on_processing_object_action (an_action: like on_processing_object_action)
			-- Set on_processing_object_action with an_action
			-- (from OBJECT_GRAPH_TRAVERSABLE)
		require -- from OBJECT_GRAPH_TRAVERSABLE
			an_action_not_void: an_action /= Void
		do
			on_processing_object_action := an_action
		ensure -- from OBJECT_GRAPH_TRAVERSABLE
			on_processing_object_action_set: on_processing_object_action = an_action
		end

	set_on_processing_reference_action (an_action: like on_processing_reference_action)
			-- Set on_processing_object_action with an_action
			-- (from OBJECT_GRAPH_TRAVERSABLE)
		require -- from OBJECT_GRAPH_TRAVERSABLE
			an_action_not_void: an_action /= Void
		do
			on_processing_reference_action := an_action
		ensure -- from OBJECT_GRAPH_TRAVERSABLE
			on_processing_reference_action_set: on_processing_reference_action = an_action
		end

	set_root_object (an_object: like root_object)
			-- Set root_object with 'an_object'.
			-- (from OBJECT_GRAPH_TRAVERSABLE)
		require -- from OBJECT_GRAPH_TRAVERSABLE
			an_object_not_void: an_object /= Void
		do
			root_object := an_object
		ensure -- from OBJECT_GRAPH_TRAVERSABLE
			root_object_set: root_object = an_object and is_root_object_set
		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: OBJECT_GRAPH_DEPTH_FIRST_TRAVERSABLE)
			-- Update current object using fields of object attached
			-- to other, so as to yield equal objects.
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
			type_identity: same_type (other)
		external
			"built_in"
		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: OBJECT_GRAPH_DEPTH_FIRST_TRAVERSABLE)
			-- 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: OBJECT_GRAPH_DEPTH_FIRST_TRAVERSABLE
			-- 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: OBJECT_GRAPH_DEPTH_FIRST_TRAVERSABLE)
			-- 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: OBJECT_GRAPH_DEPTH_FIRST_TRAVERSABLE
			-- 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: OBJECT_GRAPH_DEPTH_FIRST_TRAVERSABLE
			-- 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 OBJECT_GRAPH_DEPTH_FIRST_TRAVERSABLE
		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 OBJECT_GRAPH_DEPTH_FIRST_TRAVERSABLE
			-- 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

	frozen traverse
			-- Traverse object structure starting at 'root_object' and call object_action
			-- on every object in the graph.
			-- (from OBJECT_GRAPH_TRAVERSABLE)
		require -- from OBJECT_GRAPH_TRAVERSABLE
			root_object_available: is_root_object_set
		local
			l_marker: detachable OBJECT_GRAPH_MARKER
			l_has_lock: BOOLEAN
			l_retried: BOOLEAN
		do
			if not l_retried and then attached root_object as l_root then
				create l_marker;
				l_marker.lock_marking
				l_has_lock := True
				internal_traverse (l_root);
				l_marker.unlock_marking
				has_failed := False
			end
		rescue
			l_retried := True
			has_failed := True
			if l_has_lock and then l_marker /= Void then
				l_marker.unlock_marking
			end
			if not is_exception_propagated then
				retry
			end
		end

	wipe_out
			-- Clear current to default values
			-- (from OBJECT_GRAPH_TRAVERSABLE)
		do
			visited_objects := Void
			visited_types := Void
			object_action := Void
			root_object := Void
		ensure -- from OBJECT_GRAPH_TRAVERSABLE
			visited_objects_reset: visited_objects = Void
			object_action_not_set: not is_object_action_set
			root_object_not_set: not is_root_object_set
		end
	
feature {NONE} -- Implementation

	Default_size: INTEGER_32 = 200
			-- Default size for containers used during object traversal
			-- (from OBJECT_GRAPH_TRAVERSABLE)

	internal_traverse (a_root_object: ANY)
			-- Traverse object structure starting at 'root_object' and call object_action
			-- on every object in the graph.
			-- (from OBJECT_GRAPH_TRAVERSABLE)
		local
			i, nb: INTEGER_32
			l_object: separate ANY
			l_field: like {TUPLE}.reference_item
			l_field_type: INTEGER_32
			l_marker: OBJECT_GRAPH_MARKER
			l_objects_to_visit: like new_dispenser
			l_visited: like visited_objects
			l_visited_types: like visited_types
			l_action: like object_action
			l_on_processing_object_action: like on_processing_object_action
			l_spec: like visited_objects.area
			l_reflected_reference_object: REFLECTED_REFERENCE_OBJECT
			l_reflected_object: REFLECTED_OBJECT
			l_has_reference_with_copy_semantics: BOOLEAN
			l_on_processing_reference_action: like on_processing_reference_action
			l_referee_object_cache: REFLECTED_REFERENCE_OBJECT
			l_referee_object: REFLECTED_OBJECT
		do
			from
				create l_marker
				create l_reflected_reference_object.make (a_root_object);
				l_marker.mark (a_root_object)
				create l_visited.make (Default_size)
				create l_visited_types.make (Default_size)
				l_objects_to_visit := new_dispenser;
				l_objects_to_visit.put (a_root_object)
				l_action := object_action
				l_on_processing_object_action := on_processing_object_action
				l_on_processing_reference_action := on_processing_reference_action
				create l_referee_object_cache.make (a_root_object)
			until
				l_objects_to_visit.is_empty
			loop
				l_object := l_objects_to_visit.item;
				l_objects_to_visit.remove
				if attached {REFLECTED_OBJECT} l_object as l_copy_semantics_object then
					check
						embedded_or_copy_semantics: attached {REFLECTED_COPY_SEMANTICS_OBJECT} l_copy_semantics_object or (attached {REFLECTED_REFERENCE_OBJECT} l_copy_semantics_object as l_ref_obj and then l_ref_obj.physical_offset /= 0)
					end
					l_has_reference_with_copy_semantics := True
					l_reflected_object := l_copy_semantics_object
					if not is_skip_copy_semantics_reference then
						l_visited.extend (l_copy_semantics_object.object)
					end
				else
					l_reflected_reference_object.set_object (l_object)
					l_reflected_object := l_reflected_reference_object
					if l_reflected_reference_object.is_expanded then
						l_has_reference_with_copy_semantics := True
						if not is_skip_copy_semantics_reference then
							l_visited.extend (l_object)
						end
					else
						l_visited.extend (l_object)
					end
				end;
				l_visited_types.put (l_reflected_object.dynamic_type, l_reflected_object.dynamic_type)
				if l_action /= Void or l_on_processing_object_action /= Void then
					if not is_exception_on_copy_suppressed and then l_reflected_object.is_expanded then
						raise_unwanted_copy_exception
					else
						if l_action /= Void then
							l_action.call ([l_object])
						end
						if attached l_on_processing_object_action then
							l_on_processing_object_action.call ([l_reflected_object])
						end
					end
				end
				if l_reflected_object.is_special then
					if l_reflected_object.is_special_of_reference then
						if attached {SPECIAL [detachable ANY]} l_object as l_sp then
							from
								i := 0
								nb := l_sp.count
							until
								i = nb
							loop
								if l_reflected_object.is_special_copy_semantics_item (i) then
									l_referee_object := l_reflected_object.special_copy_semantics_item (i)
									l_field := l_referee_object;
									l_objects_to_visit.put (l_field)
									if attached l_on_processing_reference_action then
										l_on_processing_reference_action.call ([l_reflected_object, l_referee_object])
									end
								else
									l_field := l_sp.item (i)
									if l_field /= Void and then not l_marker.is_marked (l_field) then
										l_marker.mark (l_field);
										l_objects_to_visit.put (l_field)
									end
									if attached l_on_processing_reference_action and attached l_field then
										l_referee_object_cache.set_object (l_field)
										l_referee_object := l_referee_object_cache;
										l_on_processing_reference_action.call ([l_reflected_object, l_referee_object])
									end
								end
								i := i + 1
							end
						end
					elseif l_reflected_object.is_special_of_expanded then
						if attached {SPECIAL [ANY]} l_object as l_sp then
							from
								i := 0
								nb := l_sp.count
							until
								i = nb
							loop
								l_field := l_sp.item (i);
								l_objects_to_visit.put (l_field)
								if attached l_on_processing_reference_action then
									if is_exception_on_copy_suppressed then
										l_referee_object_cache.set_object (l_field)
										l_referee_object := l_referee_object_cache;
										l_on_processing_reference_action.call ([l_reflected_object, l_referee_object])
									else
										raise_unwanted_copy_exception
									end
								end
								i := i + 1
							end
						end
					end
				elseif l_reflected_object.is_tuple then
					if attached {TUPLE} l_object as l_tuple_obj then
						from
							i := 1
							nb := l_tuple_obj.count + 1
						until
							i = nb
						loop
							if l_tuple_obj.is_reference_item (i) then
								l_field := l_tuple_obj.reference_item (i)
								if l_field /= Void and then not l_marker.is_marked (l_field) then
									l_marker.mark (l_field);
									l_objects_to_visit.put (l_field)
								end
								if attached l_on_processing_reference_action and attached l_field then
									if is_exception_on_copy_suppressed then
										l_referee_object_cache.set_object (l_field)
										l_referee_object := l_referee_object_cache;
										l_on_processing_reference_action.call ([l_reflected_object, l_referee_object])
									else
										raise_unwanted_copy_exception
									end
								end
							end
							i := i + 1
						end
					end
				else
					from
						i := 1
						nb := l_reflected_object.field_count + 1
					variant
							nb - i
					until
						i = nb
					loop
						l_field_type := l_reflected_object.field_type (i)
						if l_field_type = {REFLECTOR_CONSTANTS}.reference_type or l_field_type = {REFLECTOR_CONSTANTS}.expanded_type then
							if not is_skip_transient or else not l_reflected_object.is_field_transient (i) then
								if l_field_type = {REFLECTOR_CONSTANTS}.expanded_type then
									l_referee_object := l_reflected_object.expanded_field (i);
									l_objects_to_visit.put (l_referee_object)
									if attached l_on_processing_reference_action then
										l_on_processing_reference_action.call ([l_reflected_object, l_referee_object])
									end
								elseif l_reflected_object.is_copy_semantics_field (i) then
									l_referee_object := l_reflected_object.copy_semantics_field (i);
									l_objects_to_visit.put (l_referee_object)
									if attached l_on_processing_reference_action then
										l_on_processing_reference_action.call ([l_reflected_object, l_referee_object])
									end
								else
									l_field := l_reflected_object.reference_field (i)
									if l_field /= Void then
										if not l_marker.is_marked (l_field) then
											l_marker.mark (l_field);
											l_objects_to_visit.put (l_field)
										end
										if attached l_on_processing_reference_action then
											l_referee_object_cache.set_object (l_field)
											l_referee_object := l_referee_object_cache;
											l_on_processing_reference_action.call ([l_reflected_object, l_referee_object])
										end
									end
								end
							end
						end
						i := i + 1
					end
				end
			end
			from
				i := 0
				nb := l_visited.count
				l_spec := l_visited.area
			until
				i = nb
			loop
				l_marker.unmark (l_spec.item (i))
				i := i + 1
			end
			visited_objects := l_visited
			visited_types := l_visited_types
			has_reference_with_copy_semantics := l_has_reference_with_copy_semantics
		end

	new_dispenser: ARRAYED_STACK [separate ANY]
			-- Create the dispenser to use for storing visited objects.
		do
			create Result.make (Default_size)
		ensure -- from OBJECT_GRAPH_TRAVERSABLE
			new_dispenser_not_void: Result /= Void
		end

	raise_unwanted_copy_exception
			-- (from OBJECT_GRAPH_TRAVERSABLE)
		local
			l_exception: DEVELOPER_EXCEPTION
		do
			create l_exception;
			l_exception.set_description ("An agent has been invoked on a copy of an object during object graph traversal.%NThis happens in TUPLE containing objects with copy-semantics or in SPECIAL[XX],%Nwhere XX is a user-defined expanded type.");
			l_exception.raise
		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 {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 ANY
	reflexive_equality: standard_is_equal (Current)
	reflexive_conformance: conforms_to (Current)

note
	copyright: "Copyright (c) 1984-2013, 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 OBJECT_GRAPH_DEPTH_FIRST_TRAVERSABLE

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