note
	description: "Trees, without commitment to a particular representation"
	library: "Free implementation of ELKS library"
	legal: "See notice at end of class."
	status: "See notice at end of class."
	names: tree
	access: cursor, membership
	representation: recursive
	contents: generic
	date: "$Date: 2018-11-14 15:15:17 +0000 (Wed, 14 Nov 2018) $"
	revision: "$Revision: 102463 $"

deferred class interface
	TREE [G]

feature -- Access

	parent: detachable TREE [G]
			-- Parent of current node

	child: like parent
			-- Current child node
		require
			readable: readable_child

	item: G
			-- Item in current node

	child_item: like item
			-- Item in current child node
		require
			readable: child_readable

	child_cursor: CURSOR
			-- Current cursor position

	child_index: INTEGER_32
			-- Index of current child
		ensure
			valid_index: Result >= 0 and Result <= arity + 1

	first_child: like parent
			-- Leftmost child
		require
			is_not_leaf: not is_leaf

	last_child: like first_child
			-- Right most child
		require
			is_not_leaf: not is_leaf

	left_sibling: like parent
			-- Left neighbor (if any)
		require
			is_not_root: not is_root
		ensure
			is_sibling: Result /= Void implies is_sibling (Result)
			right_is_current: (Result /= Void) implies (Result.right_sibling = Current)

	right_sibling: like parent
			-- Right neighbor (if any)
		require
			is_not_root: not is_root
		ensure
			is_sibling: Result /= Void implies is_sibling (Result)
			left_is_current: (Result /= Void) implies (Result.left_sibling = Current)
	
feature -- Measurement

	arity: INTEGER_32
			-- Number of children

	child_capacity: INTEGER_32
			-- Maximal number of children

	count: INTEGER_32
			-- Number of items
	
feature -- Comparison

	is_equal (other: like Current): BOOLEAN
			-- Does other contain the same elements?
			-- (Reference or object equality,
			-- based on object_comparison.)

	node_is_equal (other: like Current): BOOLEAN
			-- Is other equal to Current?
		require
			other_not_void: other /= Void
	
feature -- Status report

	Readable: BOOLEAN = True

	child_readable: BOOLEAN
			-- Is there a current child_item to be read?

	readable_child: BOOLEAN
			-- Is there a current child to be read?

	Writable: BOOLEAN = True
			-- Is there a current item that may be modified?

	child_writable: BOOLEAN
			-- Is there a current child_item that may be modified?

	writable_child: BOOLEAN
			-- Is there a current child that may be modified?

	child_off: BOOLEAN
			-- Is there no current child?

	child_before: BOOLEAN
			-- Is there no valid child position to the left of cursor?

	child_after: BOOLEAN
			-- Is there no valid child position to the right of cursor?

	is_empty: BOOLEAN
			-- Is structure empty of items?

	is_leaf: BOOLEAN
			-- Are there no children?

	is_root: BOOLEAN
			-- Is there no parent?

	child_isfirst: BOOLEAN
			-- Is cursor under first child?
		ensure
			not_is_leaf: Result implies not is_leaf

	child_islast: BOOLEAN
			-- Is cursor under last child?
		ensure
			not_is_leaf: Result implies not is_leaf

	valid_cursor_index (i: INTEGER_32): BOOLEAN
			-- Is i correctly bounded for cursor movement?
		ensure
			valid_cursor_index_definition: Result = (i >= 0) and (i <= child_capacity + 1)

	has (v: G): BOOLEAN
			-- Does subtree include v?
			-- (Reference or object equality,
			-- based on object_comparison.)

	is_sibling (other: attached like parent): BOOLEAN
			-- Are current node and other siblings?
		require
			other_exists: other /= Void
		ensure
			not_root: Result implies not is_root
			other_not_root: Result implies not other.is_root
			same_parent: Result = not is_root and other.parent = parent
	
feature -- Iteration

	new_cursor: TREE_ITERATION_CURSOR [G]
			-- Fresh cursor associated with current structure
	
feature -- Cursor movement

	child_go_to (p: CURSOR)
			-- Move cursor to position p.

	child_start
			-- Move cursor to first child.

	child_finish
			-- Move cursor to last child.

	child_forth
			-- Move cursor to next child.

	child_back
			-- Move cursor to previous child.

	child_go_i_th (i: INTEGER_32)
			-- Move cursor to i-th child.
		ensure then
			position: child_index = i
	
feature -- Element change

	sprout
			-- Make current node a root.

	put (v: like item)
			-- Replace element at cursor position by v.
			-- Was declared in TREE as synonym of replace.
		require
			is_writable: Writable
		ensure
			item_inserted: item = v

	replace (v: like item)
			-- Replace element at cursor position by v.
			-- Was declared in TREE as synonym of put.
		require
			is_writable: Writable
		ensure
			item_inserted: item = v

	child_put (v: like item)
			-- Put v at current child position.
			-- Was declared in TREE as synonym of child_replace.
		require
			child_writable: child_writable
		ensure
			item_inserted: child_item = v

	child_replace (v: like item)
			-- Put v at current child position.
			-- Was declared in TREE as synonym of child_put.
		require
			child_writable: child_writable
		ensure
			item_inserted: child_item = v

	put_child (n: like parent)
			-- Add n to the list of children.
			-- Do not move child cursor.
		require
			non_void_argument: n /= Void

	replace_child (n: like parent)
			-- Put n at current child position.
		require
			writable_child: writable_child
		ensure
			child_replaced: child = n

	prune (n: like Current)
			-- Remove n from the children.
		require
			is_child: n.parent = Current
		ensure
			n_is_root: n.is_root
	
feature -- Removal

	wipe_out
			-- Remove all children.
		ensure
			is_leaf: is_leaf

	forget_left
			-- Forget all left siblings.

	forget_right
			-- Forget all right siblings.
	
feature -- Conversion

	linear_representation: LINEAR [G]
			-- Representation as a linear structure

	binary_representation: BINARY_TREE [G]
			-- Convert to binary tree representation:
			-- first child becomes left child,
			-- right sibling becomes right child.
		ensure
			result_is_root: Result.is_root
			result_has_no_right_child: not Result.has_right
	
feature -- Duplication

	copy (other: like Current)
			-- Copy contents from other.
	
invariant
	tree_consistency: child_readable implies (attached child as c and then c.parent = Current)
	leaf_definition: is_leaf = (arity = 0)
	child_off_definition: child_off = child_before or child_after
	child_before_definition: child_before = (child_index = 0)
	child_isfirst_definition: child_isfirst = (not is_leaf and child_index = 1)
	child_islast_definition: child_islast = (not is_leaf and child_index = child_capacity)
	child_after_definition: child_after = (child_index >= child_capacity + 1)

note
	copyright: "Copyright (c) 1984-2018, Eiffel Software and others"
	license: "Eiffel Forum License v2 (see http://www.eiffel.com/licensing/forum.txt)"
	source: "[
		Eiffel Software
		5949 Hollister Ave., Goleta, CA 93117 USA
		Telephone 805-685-1006, Fax 805-685-6869
		Website http://www.eiffel.com
		Customer support http://support.eiffel.com
	]"

end -- class TREE

Generated by ISE EiffelStudio