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;;;; $Id: stack-m.el,v 1.1.1.1 1997/08/21 12:20:32 mrt 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
|
