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	description: "Binary tree: each node may have a left child and a right child"
	status: "See notice at end of class"
	names: binary_tree, tree, fixed_tree
	representation: recursive, array
	access: cursor, membership
	contents: generic
	date: "$Date: 2001-11-16 20:32:23 +0000 (Fri, 16 Nov 2001) $"
	revision: "$Revision: 51435 $"

class 
	BINARY_TREE [G]

inherit
	CELL [G]
		undefine
			is_equal
		redefine
			copy
		end

	TREE [G]
		redefine
			parent,
			is_leaf,
			subtree_has,
			subtree_count,
			fill_list,
			child_remove,
			child_after,
			child_capacity,
			copy
		end

create 
	make

feature -- Initialization

	make (v: like item) is
			-- Create a root node with value v.
		do
			item := v
		ensure
			is_root: is_root
			is_leaf: is_leaf
		end
	
feature -- Access

	parent: BINARY_TREE [G]
			-- Parent of current node

	child_index: INTEGER
			-- Index of cursor position

	left_child: like parent
			-- Left child, if any

	right_child: like parent
			-- Right child, if any

	left_item: like item is
			-- Value of left child
		require
			has_left: left_child /= void
		do
			Result := left_child.item
		end

	right_item: like item is
			-- Value of right child
		require
			has_right: right_child /= void
		do
			Result := right_child.item
		end

	first_child: like parent is
			-- Left child
		do
			Result := left_child
		end

	last_child: like parent is
			-- Right child
		do
			Result := right_child
		end

	child: like parent is
			-- Child at cursor position
		do
			inspect child_index
			when 1 then 
				Result := left_child
			when 2 then 
				Result := right_child
			end
		end

	child_cursor: CURSOR is
			-- Current cursor position
		do
			create {ARRAYED_LIST_CURSOR} Result.make (child_index)
		end

	left_sibling: like parent is
			-- Left neighbor, if any
		do
			if parent.right_child = Current then
				Result := parent.left_child
			end
		end

	right_sibling: like parent is
			-- Right neighbor, if any
		do
			if parent.left_child = Current then
				Result := parent.right_child
			end
		end
	
feature -- Measurement

	arity: INTEGER is
			-- Number of children
		do
			if has_left then
				Result := Result + 1
			end
			if has_right then
				Result := Result + 1
			end
		ensure then
			valid_arity: Result <= 2
		end
	
feature -- Status report

	child_after: BOOLEAN is
			-- Is there no valid child position to the right of cursor?
		do
			Result := child_index >= child_capacity + 1
		end

	is_leaf: BOOLEAN is
			-- Are there no children?
			-- Was declared in BINARY_TREE as synonym of has_none.
		do
			Result := left_child = void and right_child = void
		end

	has_none: BOOLEAN is
			-- Are there no children?
			-- Was declared in BINARY_TREE as synonym of is_leaf.
		do
			Result := left_child = void and right_child = void
		end

	has_left: BOOLEAN is
			-- Has current node a left child?
		do
			Result := left_child /= void
		ensure
			Result = (left_child /= void)
		end

	has_right: BOOLEAN is
			-- Has current node a right child?
		do
			Result := right_child /= void
		ensure
			Result = (right_child /= void)
		end

	has_both: BOOLEAN is
			-- Has current node two children?
		do
			Result := left_child /= void and right_child /= void
		ensure
			Result = (has_left and has_right)
		end
	
feature -- Cursor movement

	child_go_to (p: ARRAYED_LIST_CURSOR) is
			-- Move cursor to child remembered by p.
		do
			child_index := p.index
		end

	child_start is
			-- Move to first child.
		do
			child_index := 1
		end

	child_finish is
			-- Move cursor to last child.
		do
			child_index := 2
		end

	child_forth is
			-- Move cursor to next child.
		do
			child_index := child_index + 1
		end

	child_back is
			-- Move cursor to previous child.
		do
			child_index := child_index - 1
		end

	child_go_i_th (i: INTEGER) is
			-- Move cursor to i-th child.
		do
			child_index := i
		end
	
feature -- Element change

	put_left_child (n: like parent) is
			-- Set left_child to n.
		require
			no_parent: n = void or else n.is_root
		do
			if n /= void then
				if object_comparison then
					n.compare_objects
				else
					n.compare_references
				end
			end
			if left_child /= void then
				left_child.attach_to_parent (void)
			end
			if n /= void then
				n.attach_to_parent (Current)
			end
			left_child := n
		end

	put_right_child (n: like parent) is
			-- Set right_child to n.
		require
			no_parent: n = void or else n.is_root
		do
			if n /= void then
				if object_comparison then
					n.compare_objects
				else
					n.compare_references
				end
			end
			if right_child /= void then
				right_child.attach_to_parent (void)
			end
			if n /= void then
				n.attach_to_parent (Current)
			end
			right_child := n
		end

	child_put (v: like item) is
			-- Put v at current child position.
			-- Was declared in BINARY_TREE as synonym of child_replace.
		local
			node: like Current
		do
			if child /= void then
				if object_comparison then
					child.compare_objects
				else
					child.compare_references
				end
				child.put (v)
			else
				create node.make (v)
				if object_comparison then
					node.compare_objects
				end
				put_child (node)
			end
		end

	child_replace (v: like item) is
			-- Put v at current child position.
			-- Was declared in BINARY_TREE as synonym of child_put.
		local
			node: like Current
		do
			if child /= void then
				if object_comparison then
					child.compare_objects
				else
					child.compare_references
				end
				child.put (v)
			else
				create node.make (v)
				if object_comparison then
					node.compare_objects
				end
				put_child (node)
			end
		end

	put_child (n: like parent) is
			-- Put n at current child position.
			-- Was declared in BINARY_TREE as synonym of replace_child.
		do
			if object_comparison then
				n.compare_objects
			else
				n.compare_references
			end
			n.attach_to_parent (Current)
			inspect child_index
			when 1 then 
				left_child := n
			when 2 then 
				right_child := n
			end
		end

	replace_child (n: like parent) is
			-- Put n at current child position.
			-- Was declared in BINARY_TREE as synonym of put_child.
		do
			if object_comparison then
				n.compare_objects
			else
				n.compare_references
			end
			n.attach_to_parent (Current)
			inspect child_index
			when 1 then 
				left_child := n
			when 2 then 
				right_child := n
			end
		end
	
feature -- Removal

	remove_left_child is
			-- Remove left child.
		do
			if left_child /= void then
				left_child.attach_to_parent (void)
			end
			left_child := void
		ensure
			not has_left
		end

	remove_right_child is
			-- Remove right child.
		do
			if right_child /= void then
				right_child.attach_to_parent (void)
			end
			right_child := void
		ensure
			not has_right
		end

	child_remove is
			-- Remove current child.
		do
			inspect child_index
			when 1 then 
				left_child.attach_to_parent (void);
				left_child := void
			when 2 then 
				right_child.attach_to_parent (void);
				right_child := void
			end
		end

	prune (n: like parent) is
			-- Prune n from child nodes.
		do
			if left_child = n then
				remove_left_child
			elseif right_child = n then
				remove_right_child
			end
		end
	
feature -- Duplication

	duplicate (n: INTEGER): like Current is
			-- Copy of sub-tree beginning at cursor position and
			-- having min (n, arity - child_index + 1)
			-- children.
		do
			Result := new_tree
			if child_index <= 1 and child_index + n >= 1 and has_left then
				Result.put_left_child (left_child.duplicate_all)
			end
			if child_index <= 2 and child_index + n >= 2 and has_right then
				Result.put_right_child (right_child.duplicate_all)
			end
		end

	duplicate_all: like Current is
		do
			Result := new_tree
			if has_left then
				Result.put_left_child (left_child.duplicate_all)
			end
			if has_right then
				Result.put_right_child (right_child.duplicate_all)
			end
		end

	copy (other: like Current) is
			-- Copy contents from other.
		local
			tmp_tree: like Current
		do
			create tmp_tree.make (other.item)
			if not other.is_leaf then
				tree_copy (other, tmp_tree)
			end
		end
	
feature {BINARY_TREE} -- Implementation

	fill_list (al: ARRAYED_LIST [G]) is
			-- Fill al with all the children's items.
		do
			if left_child /= void then
				al.extend (left_child.item)
				left_child.fill_list (al)
			end
			if right_child /= void then
				al.extend (right_child.item)
				right_child.fill_list (al)
			end
		end
	
feature {NONE} -- Implementation

	subtree_has (v: G): BOOLEAN is
			-- Does subtree contain v?
		do
			if left_child /= void then
				Result := left_child.has (v)
			end
			if right_child /= void and not Result then
				Result := right_child.has (v)
			end
		end

	subtree_count: INTEGER is
			-- Number of items in subtree
		do
			if left_child /= void then
				Result := left_child.count
			end
			if right_child /= void then
				Result := Result + right_child.count
			end
		end

	fill_subtree (other: BINARY_TREE [G]) is
			-- Copy other to subtee.
		do
			if not other.is_leaf then
				put_left_child (other.left_child.duplicate_all)
			end
			if other.arity >= 2 then
				put_right_child (other.right_child.duplicate_all)
			end
		end

	new_tree: like Current is
			-- New tree node
		do
			create Result.make (item)
			if object_comparison then
				Result.compare_objects
			end
		end

	Child_capacity: INTEGER is 2
	
invariant

	tree_is_binary: child_capacity = 2

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 BINARY_TREE


Classes
Clusters
Cluster hierarchy
Chart
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Text
Flat
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Flat contracts
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