--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lisp/skk/stack-m.el	Mon Aug 13 10:09:35 2007 +0200
@@ -0,0 +1,116 @@
+;;;; $Id: stack-m.el,v 1.1 1997/12/02 08:48:41 steve Exp $
+;;;; This file implements a simple LIFO stack using macros.
+
+;; Copyright (C) 1991-1995 Free Software Foundation
+
+;; Author: Inge Wallin <inge@lysator.liu.se>
+;; Maintainer: elib-maintainers@lysator.liu.se
+;; Created: 12 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:
+
+;;; The stack is implemented as a linked list with a tag 'STACK
+;;; as the first element.  All entries and removals are done using
+;;; destructive functions.
+;;;
+;;; This file implements the functions as macros for speed in compiled 
+;;; code.
+;;;
+
+
+;;; Code:
+
+;; Provide the function version and remove the macro version
+(provide 'stack-m)
+(setq features (delq 'stack-f features))
+
+
+;;; ================================================================
+
+
+(defmacro stack-create ()
+  "Create an empty lifo stack."
+  (` (cons 'STACK nil)))
+
+
+(defmacro stack-p (stack)
+  "Return t if STACK is a stack, otherwise return nil."
+  (` (eq (car-safe (, stack)) 'STACK)))
+
+
+(defmacro stack-push (stack element)
+  "Push an element onto the stack.
+Args: STACK ELEMENT"
+  (` (setcdr (, stack) (cons (, element) (cdr (, stack))))))
+
+
+(defmacro stack-pop (stack)
+  "Remove the topmost element from STACK and return it. 
+If the stack is empty, return nil."
+  (` (prog1
+	 (car-safe (cdr (, stack)))
+       (setcdr (, stack) (cdr-safe (cdr (, stack)))))))
+
+
+(defmacro stack-empty (stack)
+  "Return t if STACK is empty, otherwise return nil."
+  (` (null (cdr (, stack)))))
+
+
+(defmacro stack-top (stack)
+  "Return the topmost element of STACK or nil if it is empty."
+  (` (car-safe (cdr (, stack)))))
+
+
+(defmacro stack-nth (stack n)
+  "Return nth element of a stack, but don't remove it.
+Args: STACK N
+If the length of the stack is less than N, return nil.
+
+The top stack element has number 0."
+  (` (nth (, n) (cdr (, stack)))))
+
+
+(defmacro stack-all (stack)
+  "Return a list of all entries in STACK.
+The element last pushed is first in the list."
+  (` (cdr (, stack))))
+
+
+(defmacro stack-copy (stack)
+  "Return a copy of STACK.
+All entries in STACK are also copied."
+  (` (cons 'STACK (copy-sequence (cdr (, stack))))))
+
+
+(defmacro stack-length (stack)
+  "Return the number of elements on STACK."
+  (` (length (cdr (, stack)))))
+
+
+(defmacro stack-clear (stack)
+  "Remove all elements from STACK."
+  (` (setcdr (, stack) nil)))
+
+;;; stack-m.el ends here