indexing
	description: "[
		Objects that are able to iterate over cursor trees, 
		on which they can perform repeated actions and tests according
		to a number of predefined control structures such as ``if'',
		``until'' and others.
	]"
	legal: "See notice at end of class."
	status: "See notice at end of class."
	names: iterators, iteration, cursor_tree_iterators, cursor_tree_iteration, tree_iterators, tree_iteration
	exploration: depth_first, breadth_first
	traversal: preorder, postorder, inorder
	date: "$Date: 2007-01-14 01:47:13 -0800 (Sun, 14 Jan 2007) $"
	revision: "$Revision: 55 $"

class interface
	CURSOR_TREE_ITERATOR [G]


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

feature -- Initialization

	set (s: like target)
			-- Make `s' the new target of iterations.
			-- (from LINEAR_ITERATOR)
		require -- from ITERATOR
			target_exists: s /= Void
		ensure -- from ITERATOR
			target = s
			target /= Void
	
feature -- Access

	generating_type: STRING_8
			-- Name of current object's generating type
			-- (type of which it is a direct instance)
			-- (from ANY)
		ensure -- from ANY
			generating_type_not_void: Result /= Void
			generating_type_not_empty: not Result.is_empty

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

	item: G
			-- The item at cursor position in target
			-- (from LINEAR_ITERATOR)
		require -- from LINEAR_ITERATOR
			not_off: not target.off

	item_tuple: TUPLE [G]
			-- Tuple containing a single element,
			-- the item at cursor position in target''
			-- (from LINEAR_ITERATOR)
		require -- from LINEAR_ITERATOR
			not_off: not target.off
	
feature -- Comparison

	frozen deep_equal (some: ?ANY; other: like arg #1): BOOLEAN
			-- Are `some' and `other' either both void
			-- or attached to isomorphic object structures?
			-- (from ANY)
		ensure -- from ANY
			shallow_implies_deep: standard_equal (some, other) implies Result
			both_or_none_void: (some = Void) implies (Result = (other = Void))
			same_type: (Result and (some /= Void)) implies (other /= Void and then some.same_type (other))
			symmetric: Result implies deep_equal (other, some)

	frozen equal (some: ?ANY; other: like arg #1): BOOLEAN
			-- Are `some' and `other' either both void or attached
			-- to objects considered equal?
			-- (from ANY)
		ensure -- from ANY
			definition: Result = (some = Void and other = Void) or else ((some /= Void and other /= Void) and then some.is_equal (other))

	frozen is_deep_equal (other: CURSOR_TREE_ITERATOR [G]): BOOLEAN
			-- Are `Current' and `other' attached to isomorphic object structures?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		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)

	is_equal (other: CURSOR_TREE_ITERATOR [G]): BOOLEAN
			-- Is `other' attached to an object considered
			-- equal to current object?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		ensure -- from ANY
			symmetric: Result implies other.is_equal (Current)
			consistent: standard_is_equal (other) implies Result

	frozen standard_equal (some: ?ANY; other: like arg #1): BOOLEAN
			-- Are `some' and `other' either both void or attached to
			-- field-by-field identical objects of the same type?
			-- Always uses default object comparison criterion.
			-- (from ANY)
		ensure -- from ANY
			definition: Result = (some = Void and other = Void) or else ((some /= Void and other /= Void) and then some.standard_is_equal (other))

	frozen standard_is_equal (other: CURSOR_TREE_ITERATOR [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
		ensure -- from ANY
			same_type: Result implies same_type (other)
			symmetric: Result implies other.standard_is_equal (Current)
	
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

	invariant_value: BOOLEAN
			-- Is the invariant satisfied?
			-- (Redefinitions of this feature will usually involve
			-- target; if so, make sure that the result is defined
			-- when `target = Void'.)
			-- (from ITERATOR)

	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
		ensure -- from ANY
			definition: Result = (conforms_to (other) and other.conforms_to (Current))

	target: CURSOR_TREE [G]
			-- The structure to which iteration features will apply
	
feature -- Cursor movement

	breadth_forth
			-- Move cursor of target to next position in breadth-first.

	breadth_start
			-- Move cursor of target to root position
			-- (first position in preorder and breadth-first).
			-- Was declared in CURSOR_TREE_ITERATOR as synonym of pre_start.

	exhausted: BOOLEAN
			-- Is target exhausted?
			-- (from LINEAR_ITERATOR)

	off: BOOLEAN
			-- Is position of target off?
			-- (from LINEAR_ITERATOR)

	post_forth
			-- Move cursor of target to next position in postorder.

	post_start
			-- Move cursor of target to first position in postorder.

	pre_forth
			-- Move cursor of target to next position in preorder.

	pre_start
			-- Move cursor of target to root position
			-- (first position in preorder and breadth-first).
			-- Was declared in CURSOR_TREE_ITERATOR as synonym of breadth_start.

	start
			-- Move to first position of target.
			-- (from LINEAR_ITERATOR)
	
feature -- Duplication

	copy (other: CURSOR_TREE_ITERATOR [G])
			-- 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)
		ensure -- from ANY
			is_equal: is_equal (other)

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

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

	frozen standard_copy (other: CURSOR_TREE_ITERATOR [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)
		ensure -- from ANY
			is_standard_equal: standard_is_equal (other)

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

	frozen twin: CURSOR_TREE_ITERATOR [G]
			-- New object equal to `Current'
			-- twin calls copy; to change copying/twining semantics, redefine copy.
			-- (from ANY)
		ensure -- from ANY
			twin_not_void: Result /= Void
			is_equal: Result.is_equal (Current)
	
feature -- Basic operations

	frozen default: ?CURSOR_TREE_ITERATOR [G]
			-- Default value of object's type
			-- (from ANY)

	frozen default_pointer: POINTER
			-- Default value of type `POINTER'
			-- (Avoid the need to write `p'.default for
			-- some `p' of type `POINTER'.)
			-- (from ANY)

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

	frozen do_nothing
			-- Execute a null action.
			-- (from ANY)
	
feature -- Implementation

	internal_item_tuple: TUPLE [G]
			-- Field holding the last item of target
			-- (from LINEAR_ITERATOR)
	
feature -- Iteration

	breadth_continue_for (action: PROCEDURE [ANY, TUPLE [G]]; n, k: INTEGER_32)
			-- Apply `action' to every `k'-th item,
			-- `n' times if possible.
			-- (from LINEAR_ITERATOR)
		require -- from LINEAR_ITERATOR
			valid_repetition: n >= 0
			valid_skip: k >= 1

	post_continue_for (action: PROCEDURE [ANY, TUPLE [G]]; n, k: INTEGER_32)
			-- Apply `action' to every `k'-th item,
			-- `n' times if possible.
			-- (from LINEAR_ITERATOR)
		require -- from LINEAR_ITERATOR
			valid_repetition: n >= 0
			valid_skip: k >= 1

	pre_continue_for (action: PROCEDURE [ANY, TUPLE [G]]; n, k: INTEGER_32)
			-- Apply `action' to every `k'-th item,
			-- `n' times if possible.
			-- (from LINEAR_ITERATOR)
		require -- from LINEAR_ITERATOR
			valid_repetition: n >= 0
			valid_skip: k >= 1

	breadth_continue_search (test: FUNCTION [ANY, TUPLE [G], BOOLEAN]; b: BOOLEAN)
			-- Search the first item of target
			-- satisfying: `test' equals to `b'
			-- (from the current position of target).
			-- (from LINEAR_ITERATOR)
		ensure then -- from LINEAR_ITERATOR
			found: not exhausted = (b = test.item (item_tuple))

	post_continue_search (test: FUNCTION [ANY, TUPLE [G], BOOLEAN]; b: BOOLEAN)
			-- Search the first item of target
			-- satisfying: `test' equals to `b'
			-- (from the current position of target).
			-- (from LINEAR_ITERATOR)
		ensure then -- from LINEAR_ITERATOR
			found: not exhausted = (b = test.item (item_tuple))

	pre_continue_search (test: FUNCTION [ANY, TUPLE [G], BOOLEAN]; b: BOOLEAN)
			-- Search the first item of target
			-- satisfying: `test' equals to `b'
			-- (from the current position of target).
			-- (from LINEAR_ITERATOR)
		ensure then -- from LINEAR_ITERATOR
			found: not exhausted = (b = test.item (item_tuple))

	post_continue_until (action: PROCEDURE [ANY, TUPLE [G]]; test: FUNCTION [ANY, TUPLE [G], BOOLEAN])
			-- Apply `action' to every item of target up to
			-- and including first one satisfying `test'.
			-- (from the current position of target).
			-- (from LINEAR_ITERATOR)
		require -- from LINEAR_ITERATOR
			invariant_satisfied: invariant_value
		ensure then -- from LINEAR_ITERATOR
			achieved: not exhausted implies test.item (item_tuple)

	breadth_continue_until (action: PROCEDURE [ANY, TUPLE [G]]; test: FUNCTION [ANY, TUPLE [G], BOOLEAN])
			-- Apply `action' to every item of target up to
			-- and including first one satisfying `test'.
			-- (from the current position of target).
			-- (from LINEAR_ITERATOR)
		require -- from LINEAR_ITERATOR
			invariant_satisfied: invariant_value
		ensure then -- from LINEAR_ITERATOR
			achieved: not exhausted implies test.item (item_tuple)

	pre_continue_until (action: PROCEDURE [ANY, TUPLE [G]]; test: FUNCTION [ANY, TUPLE [G], BOOLEAN])
			-- Apply `action' to every item of target up to
			-- and including first one satisfying `test'.
			-- (from the current position of target).
			-- (from LINEAR_ITERATOR)
		require -- from LINEAR_ITERATOR
			invariant_satisfied: invariant_value
		ensure then -- from LINEAR_ITERATOR
			achieved: not exhausted implies test.item (item_tuple)

	pre_continue_while (action: PROCEDURE [ANY, TUPLE [G]]; test: FUNCTION [ANY, TUPLE [G], BOOLEAN])
			-- Apply `action' to every item of target up to
			-- and including first one not satisfying `test'
			-- (from the current position of target).
			-- (from LINEAR_ITERATOR)
		require else -- from LINEAR_ITERATOR
			invariant_satisfied: invariant_value
		ensure then -- from LINEAR_ITERATOR
			finished: not exhausted implies not test.item (item_tuple)

	post_continue_while (action: PROCEDURE [ANY, TUPLE [G]]; test: FUNCTION [ANY, TUPLE [G], BOOLEAN])
			-- Apply `action' to every item of target up to
			-- and including first one not satisfying `test'
			-- (from the current position of target).
			-- (from LINEAR_ITERATOR)
		require else -- from LINEAR_ITERATOR
			invariant_satisfied: invariant_value
		ensure then -- from LINEAR_ITERATOR
			finished: not exhausted implies not test.item (item_tuple)

	breadth_continue_while (action: PROCEDURE [ANY, TUPLE [G]]; test: FUNCTION [ANY, TUPLE [G], BOOLEAN])
			-- Apply `action' to every item of target up to
			-- and including first one not satisfying `test'
			-- (from the current position of target).
			-- (from LINEAR_ITERATOR)
		require else -- from LINEAR_ITERATOR
			invariant_satisfied: invariant_value
		ensure then -- from LINEAR_ITERATOR
			finished: not exhausted implies not test.item (item_tuple)

	post_do_all (action: PROCEDURE [ANY, TUPLE [G]])
			-- Apply `action' to every item of target.
			-- (from ITERATOR)
		require -- from ITERATOR
			action_exists: action /= Void

	breadth_do_all (action: PROCEDURE [ANY, TUPLE [G]])
			-- Apply `action' to every item of target.
			-- (from ITERATOR)
		require -- from ITERATOR
			action_exists: action /= Void

	pre_do_all (action: PROCEDURE [ANY, TUPLE [G]])
			-- Apply `action' to every item of target.
			-- (from ITERATOR)
		require -- from ITERATOR
			action_exists: action /= Void

	pre_do_for (action: PROCEDURE [ANY, TUPLE [G]]; i, n, k: INTEGER_32)
			-- Apply `action' to every `k'-th item,
			-- `n' times if possible, starting from `i'-th.
			-- (from LINEAR_ITERATOR)
		require -- from LINEAR_ITERATOR
			valid_start: i >= 1
			valid_repetition: n >= 0
			valid_skip: k >= 1

	breadth_do_for (action: PROCEDURE [ANY, TUPLE [G]]; i, n, k: INTEGER_32)
			-- Apply `action' to every `k'-th item,
			-- `n' times if possible, starting from `i'-th.
			-- (from LINEAR_ITERATOR)
		require -- from LINEAR_ITERATOR
			valid_start: i >= 1
			valid_repetition: n >= 0
			valid_skip: k >= 1

	post_do_for (action: PROCEDURE [ANY, TUPLE [G]]; i, n, k: INTEGER_32)
			-- Apply `action' to every `k'-th item,
			-- `n' times if possible, starting from `i'-th.
			-- (from LINEAR_ITERATOR)
		require -- from LINEAR_ITERATOR
			valid_start: i >= 1
			valid_repetition: n >= 0
			valid_skip: k >= 1

	post_do_if (action: PROCEDURE [ANY, TUPLE [G]]; test: FUNCTION [ANY, TUPLE [G], BOOLEAN])
			-- Apply `action' to every item of target satisfying `test'.
			-- (from ITERATOR)
		require -- from ITERATOR
			action_exists: action /= Void
			test_exists: test /= Void

	pre_do_if (action: PROCEDURE [ANY, TUPLE [G]]; test: FUNCTION [ANY, TUPLE [G], BOOLEAN])
			-- Apply `action' to every item of target satisfying `test'.
			-- (from ITERATOR)
		require -- from ITERATOR
			action_exists: action /= Void
			test_exists: test /= Void

	breadth_do_if (action: PROCEDURE [ANY, TUPLE [G]]; test: FUNCTION [ANY, TUPLE [G], BOOLEAN])
			-- Apply `action' to every item of target satisfying `test'.
			-- (from ITERATOR)
		require -- from ITERATOR
			action_exists: action /= Void
			test_exists: test /= Void

	breadth_do_until (action: PROCEDURE [ANY, TUPLE [G]]; test: FUNCTION [ANY, TUPLE [G], BOOLEAN])
			-- Apply `action' to every item of target up to
			-- and including first one satisfying `test'.
			-- (from LINEAR_ITERATOR)
		require -- from ITERATOR
			action_exists: action /= Void
			test_exists: test /= Void
		ensure then -- from LINEAR_ITERATOR
			achieved: not exhausted implies test.item (item_tuple)

	pre_do_until (action: PROCEDURE [ANY, TUPLE [G]]; test: FUNCTION [ANY, TUPLE [G], BOOLEAN])
			-- Apply `action' to every item of target up to
			-- and including first one satisfying `test'.
			-- (from LINEAR_ITERATOR)
		require -- from ITERATOR
			action_exists: action /= Void
			test_exists: test /= Void
		ensure then -- from LINEAR_ITERATOR
			achieved: not exhausted implies test.item (item_tuple)

	post_do_until (action: PROCEDURE [ANY, TUPLE [G]]; test: FUNCTION [ANY, TUPLE [G], BOOLEAN])
			-- Apply `action' to every item of target up to
			-- and including first one satisfying `test'.
			-- (from LINEAR_ITERATOR)
		require -- from ITERATOR
			action_exists: action /= Void
			test_exists: test /= Void
		ensure then -- from LINEAR_ITERATOR
			achieved: not exhausted implies test.item (item_tuple)

	pre_do_while (action: PROCEDURE [ANY, TUPLE [G]]; test: FUNCTION [ANY, TUPLE [G], BOOLEAN])
			-- Apply `action' to every item of target up to
			-- and including first one not satisfying `test'.
			-- (from the start of target)
			-- (from LINEAR_ITERATOR)
		require -- from ITERATOR
			action_exists: action /= Void
			test_exists: test /= Void
		ensure then -- from LINEAR_ITERATOR
			finished: not exhausted implies not test.item (item_tuple)

	breadth_do_while (action: PROCEDURE [ANY, TUPLE [G]]; test: FUNCTION [ANY, TUPLE [G], BOOLEAN])
			-- Apply `action' to every item of target up to
			-- and including first one not satisfying `test'.
			-- (from the start of target)
			-- (from LINEAR_ITERATOR)
		require -- from ITERATOR
			action_exists: action /= Void
			test_exists: test /= Void
		ensure then -- from LINEAR_ITERATOR
			finished: not exhausted implies not test.item (item_tuple)

	post_do_while (action: PROCEDURE [ANY, TUPLE [G]]; test: FUNCTION [ANY, TUPLE [G], BOOLEAN])
			-- Apply `action' to every item of target up to
			-- and including first one not satisfying `test'.
			-- (from the start of target)
			-- (from LINEAR_ITERATOR)
		require -- from ITERATOR
			action_exists: action /= Void
			test_exists: test /= Void
		ensure then -- from LINEAR_ITERATOR
			finished: not exhausted implies not test.item (item_tuple)

	pre_for_all (test: FUNCTION [ANY, TUPLE [G], BOOLEAN]): BOOLEAN
			-- Does `test' return true for
			-- all items of target?
			-- (from LINEAR_ITERATOR)
		require -- from ITERATOR
			test_exists: test /= Void

	breadth_for_all (test: FUNCTION [ANY, TUPLE [G], BOOLEAN]): BOOLEAN
			-- Does `test' return true for
			-- all items of target?
			-- (from LINEAR_ITERATOR)
		require -- from ITERATOR
			test_exists: test /= Void

	post_for_all (test: FUNCTION [ANY, TUPLE [G], BOOLEAN]): BOOLEAN
			-- Does `test' return true for
			-- all items of target?
			-- (from LINEAR_ITERATOR)
		require -- from ITERATOR
			test_exists</