--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lisp/pcl-cvs/elib-node.el	Mon Aug 13 08:45:50 2007 +0200
@@ -0,0 +1,109 @@
+;;;; $Id: elib-node.el,v 1.1.1.1 1996/12/18 03:32:27 steve Exp $
+;;;; Nodes used in binary trees and doubly linked lists.
+
+;; Copyright (C) 1991-1995 Free Software Foundation
+
+;; Author: Per Cederqvist <ceder@lysator.liu.se>
+;;	Inge Wallin <inge@lysator.liu.se>
+;; Maintainer: elib-maintainers@lysator.liu.se
+;; Created: 20 May 1991
+;; Keywords: extensions, lisp
+
+;;;; This file is part of the GNU Emacs lisp library, Elib.
+;;;;
+;;;; GNU Elib is free software; you can redistribute it and/or modify
+;;;; it under the terms of the GNU General Public License as published by
+;;;; the Free Software Foundation; either version 2, or (at your option)
+;;;; any later version.
+;;;;
+;;;; GNU Elib is distributed in the hope that it will be useful,
+;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;;; GNU General Public License for more details.
+;;;;
+;;;; You should have received a copy of the GNU General Public License
+;;;; along with GNU Elib; see the file COPYING.  If not, write to
+;;;; the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+;;;; Boston, MA 02111-1307, USA
+;;;;
+;;;; Author: Inge Wallin
+;;;; 
+
+;;; Commentary:
+
+;;; A node is implemented as an array with three elements, using
+;;; (elt node 0) as the left pointer
+;;; (elt node 1) as the right pointer
+;;; (elt node 2) as the data
+;;;
+;;; Some types of trees, e.g. AVL trees, need bigger nodes, but 
+;;; as long as the first three parts are the left pointer, the 
+;;; right pointer and the data field, these macros can be used.
+;;;
+
+;;; Code:
+
+(provide 'elib-node)
+
+
+(defmacro elib-node-create (left right data)
+
+  ;; Create a tree node from LEFT, RIGHT and DATA.
+  (` (vector (, left) (, right) (, data))))
+
+
+(defmacro elib-node-left (node)
+
+  ;; Return the left pointer of NODE.
+  (` (aref (, node) 0)))
+
+
+(defmacro elib-node-right (node)
+
+  ;; Return the right pointer of NODE.
+  (` (aref (, node) 1)))
+
+
+(defmacro elib-node-data (node)
+
+  ;; Return the data of NODE.
+  (` (aref (, node) 2)))
+
+
+(defmacro elib-node-set-left (node newleft)
+
+  ;; Set the left pointer of NODE to NEWLEFT.
+  (` (aset (, node) 0 (, newleft))))
+
+
+(defmacro elib-node-set-right (node newright)
+
+  ;; Set the right pointer of NODE to NEWRIGHT.
+  (` (aset (, node) 1 (, newright))))
+
+
+(defmacro elib-node-set-data (node newdata)
+  ;; Set the data of NODE to NEWDATA.
+  (` (aset (, node) 2 (, newdata))))
+
+
+
+(defmacro elib-node-branch (node branch)
+
+  ;; Get value of a branch of a node.
+  ;; 
+  ;; NODE is the node, and BRANCH is the branch.
+  ;; 0 for left pointer, 1 for right pointer and 2 for the data."
+  (` (aref (, node) (, branch))))
+
+
+(defmacro elib-node-set-branch (node branch newval)
+
+  ;; Set value of a branch of a node.
+  ;;
+  ;; NODE is the node, and BRANCH is the branch.
+  ;; 0 for left pointer, 1 for the right pointer and 2 for the data.
+  ;; NEWVAL is new value of the branch."
+  (` (aset (, node) (, branch) (, newval))))
+
+;;; elib-node.el ends here.