;;;; $Id: elib-node.el,v 0.8 1995/12/11 00:11:19 ceder 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.
