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1 ;;;; $Id: stack-m.el,v 1.1 1997/12/02 08:48:41 steve Exp $
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2 ;;;; This file implements a simple LIFO stack using macros.
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3
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4 ;; Copyright (C) 1991-1995 Free Software Foundation
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5
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6 ;; Author: Inge Wallin <inge@lysator.liu.se>
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7 ;; Maintainer: elib-maintainers@lysator.liu.se
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8 ;; Created: 12 May 1991
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9 ;; Keywords: extensions, lisp
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10
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11 ;;;; This file is part of the GNU Emacs lisp library, Elib.
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12 ;;;;
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13 ;;;; GNU Elib is free software; you can redistribute it and/or modify
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14 ;;;; it under the terms of the GNU General Public License as published by
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15 ;;;; the Free Software Foundation; either version 2, or (at your option)
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16 ;;;; any later version.
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17 ;;;;
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18 ;;;; GNU Elib is distributed in the hope that it will be useful,
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19 ;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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20 ;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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21 ;;;; GNU General Public License for more details.
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22 ;;;;
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23 ;;;; You should have received a copy of the GNU General Public License
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24 ;;;; along with GNU Elib; see the file COPYING. If not, write to
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25 ;;;; the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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26 ;;;; Boston, MA 02111-1307, USA
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27 ;;;;
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28 ;;;; Author: Inge Wallin
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29 ;;;;
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30
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31 ;;; Commentary:
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32
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33 ;;; The stack is implemented as a linked list with a tag 'STACK
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34 ;;; as the first element. All entries and removals are done using
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35 ;;; destructive functions.
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36 ;;;
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37 ;;; This file implements the functions as macros for speed in compiled
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38 ;;; code.
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39 ;;;
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40
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41
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42 ;;; Code:
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43
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44 ;; Provide the function version and remove the macro version
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45 (provide 'stack-m)
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46 (setq features (delq 'stack-f features))
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47
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48
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49 ;;; ================================================================
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50
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51
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52 (defmacro stack-create ()
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53 "Create an empty lifo stack."
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54 (` (cons 'STACK nil)))
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55
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56
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57 (defmacro stack-p (stack)
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58 "Return t if STACK is a stack, otherwise return nil."
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59 (` (eq (car-safe (, stack)) 'STACK)))
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60
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61
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62 (defmacro stack-push (stack element)
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63 "Push an element onto the stack.
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64 Args: STACK ELEMENT"
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65 (` (setcdr (, stack) (cons (, element) (cdr (, stack))))))
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66
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67
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68 (defmacro stack-pop (stack)
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69 "Remove the topmost element from STACK and return it.
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70 If the stack is empty, return nil."
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71 (` (prog1
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72 (car-safe (cdr (, stack)))
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73 (setcdr (, stack) (cdr-safe (cdr (, stack)))))))
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74
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75
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76 (defmacro stack-empty (stack)
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77 "Return t if STACK is empty, otherwise return nil."
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78 (` (null (cdr (, stack)))))
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79
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80
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81 (defmacro stack-top (stack)
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82 "Return the topmost element of STACK or nil if it is empty."
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83 (` (car-safe (cdr (, stack)))))
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84
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85
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86 (defmacro stack-nth (stack n)
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87 "Return nth element of a stack, but don't remove it.
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88 Args: STACK N
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89 If the length of the stack is less than N, return nil.
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90
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91 The top stack element has number 0."
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92 (` (nth (, n) (cdr (, stack)))))
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93
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94
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95 (defmacro stack-all (stack)
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96 "Return a list of all entries in STACK.
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97 The element last pushed is first in the list."
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98 (` (cdr (, stack))))
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99
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100
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101 (defmacro stack-copy (stack)
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102 "Return a copy of STACK.
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103 All entries in STACK are also copied."
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104 (` (cons 'STACK (copy-sequence (cdr (, stack))))))
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105
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106
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107 (defmacro stack-length (stack)
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108 "Return the number of elements on STACK."
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109 (` (length (cdr (, stack)))))
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110
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111
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112 (defmacro stack-clear (stack)
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113 "Remove all elements from STACK."
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114 (` (setcdr (, stack) nil)))
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115
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116 ;;; stack-m.el ends here
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