lisp/play/life.el

   1 ;;; life.el --- John Horton Conway's `Life' game for GNU Emacs
   2
   3 ;; Copyright (C) 1988, 2001, 2002, 2003, 2004,
   4 ;;   2005, 2006, 2007, 2008 Free Software Foundation, Inc.
   5
   6 ;; Author: Kyle Jones <kyleuunet.uu.net>
   7 ;; Maintainer: FSF
   8 ;; Keywords: games
   9
  10 ;; This file is part of GNU Emacs.
  11
  12 ;; GNU Emacs is free software; you can redistribute it and/or modify
  13 ;; it under the terms of the GNU General Public License as published by
  14 ;; the Free Software Foundation; either version 3, or (at your option)
  15 ;; any later version.
  16
  17 ;; GNU Emacs is distributed in the hope that it will be useful,
  18 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  19 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20 ;; GNU General Public License for more details.
  21
  22 ;; You should have received a copy of the GNU General Public License
  23 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  24 ;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  25 ;; Boston, MA 02110-1301, USA.
  26
  27 ;;; Commentary:
  28
  29 ;; A demonstrator for John Horton Conway's "Life" cellular automaton
  30 ;; in Emacs Lisp.  Picks a random one of a set of interesting Life
  31 ;; patterns and evolves it according to the familiar rules.
  32
  33 ;;; Code:
  34
  35 (defvar life-patterns
  36   [("@@@" " @@" "@@@")
  37    ("@@@ @@@" "@@  @@ " "@@@ @@@")
  38    ("@@@ @@@" "@@   @@" "@@@ @@@")
  39    ("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@")
  40    ("@@@@@@@@@@")
  41    ("   @@@@@@@@@@       "
  42     "     @@@@@@@@@@     "
  43     "       @@@@@@@@@@   "
  44     "@@@@@@@@@@          "
  45     "@@@@@@@@@@          ")
  46    ("@" "@" "@" "@" "@" "@" "@" "@" "@" "@" "@" "@" "@" "@" "@")
  47    ("@               @" "@               @"  "@               @"
  48     "@               @" "@               @"  "@               @"
  49     "@               @" "@               @"  "@               @"
  50     "@               @" "@               @"  "@               @"
  51     "@               @" "@               @"  "@               @")
  52    ("@@               " " @@              " "  @@             "
  53     "   @@            " "    @@           " "     @@          "
  54     "      @@         " "       @@        " "        @@       "
  55     "         @@      " "          @@     " "           @@    "
  56     "            @@   " "             @@  " "              @@ "
  57     "               @@")
  58    ("@@@@@@@@@" "@   @   @" "@ @@@@@ @" "@ @   @ @" "@@@   @@@"
  59     "@ @   @ @" "@ @@@@@ @" "@   @   @" "@@@@@@@@@")
  60    ("                        @           "
  61     "                      @ @           "
  62     "            @@      @@            @@"
  63     "           @   @    @@            @@"
  64     "@@        @     @   @@              "
  65     "@@        @   @ @@    @ @           "
  66     "          @     @       @           "
  67     "           @   @                    "
  68     "            @@                      ")
  69    ("      @ "
  70     "    @ @@"
  71     "    @ @ "
  72     "    @   "
  73     "  @     "
  74     "@ @     ")
  75    ("@@@ @"
  76     "@    "
  77     "   @@"
  78     " @@ @"
  79     "@ @ @")
  80    ("@@@@@@@@ @@@@@   @@@      @@@@@@@ @@@@@")]
  81   "Vector of rectangles containing some Life startup patterns.")
  82
  83 ;; Macros are used macros for manifest constants instead of variables
  84 ;; because the compiler will convert them to constants, which should
  85 ;; eval faster than symbols.
  86 ;;
  87 ;; Don't change any of the life-* macro constants unless you thoroughly
  88 ;; understand the `life-grim-reaper' function.
  89
  90 (defmacro life-life-char () ?@)
  91 (defmacro life-death-char () (1+ (life-life-char)))
  92 (defmacro life-birth-char () 3)
  93 (defmacro life-void-char () ?\ )
  94
  95 (defmacro life-life-string () (char-to-string (life-life-char)))
  96 (defmacro life-death-string () (char-to-string (life-death-char)))
  97 (defmacro life-birth-string () (char-to-string (life-birth-char)))
  98 (defmacro life-void-string () (char-to-string (life-void-char)))
  99 (defmacro life-not-void-regexp () (concat "[^" (life-void-string) "\n]"))
 100
 101 (defmacro life-increment (variable) (list 'setq variable (list '1+ variable)))
 102
 103
 104 ;; list of numbers that tell how many characters to move to get to
 105 ;; each of a cell's eight neighbors.
 106 (defvar life-neighbor-deltas nil)
 107
 108 ;; window display always starts here.  Easier to deal with than
 109 ;; (scroll-up) and (scroll-down) when trying to center the display.
 110 (defvar life-window-start nil)
 111
 112 ;; For mode line
 113 (defvar life-current-generation nil)
 114 ;; Sadly, mode-line-format won't display numbers.
 115 (defvar life-generation-string nil)
 116
 117 (defvar life-initialized nil
 118   "Non-nil if `life' has been run at least once.")
 119
 120 ;;;###autoload
 121 (defun life (&optional sleeptime)
 122   "Run Conway's Life simulation.
 123 The starting pattern is randomly selected.  Prefix arg (optional first
 124 arg non-nil from a program) is the number of seconds to sleep between
 125 generations (this defaults to 1)."
 126   (interactive "p")
 127   (or life-initialized
 128       (random t))
 129   (setq life-initialized t)
 130   (or sleeptime (setq sleeptime 1))
 131   (life-setup)
 132   (catch 'life-exit
 133     (while t
 134       (let ((inhibit-quit t))
 135         (life-display-generation sleeptime)
 136         (life-grim-reaper)
 137         (life-expand-plane-if-needed)
 138         (life-increment-generation)))))
 139
 140 (defalias 'life-mode 'life)
 141 (put 'life-mode 'mode-class 'special)
 142
 143 (defun life-setup ()
 144   (let (n)
 145     (switch-to-buffer (get-buffer-create "*Life*") t)
 146     (erase-buffer)
 147     (kill-all-local-variables)
 148     (setq case-fold-search nil
 149           mode-name "Life"
 150           major-mode 'life-mode
 151           truncate-lines t
 152           show-trailing-whitespace nil
 153           life-current-generation 0
 154           life-generation-string "0"
 155           mode-line-buffer-identification '("Life: generation "
 156                                             life-generation-string)
 157           fill-column (1- (window-width))
 158           life-window-start 1)
 159     (buffer-disable-undo (current-buffer))
 160     ;; stuff in the random pattern
 161     (life-insert-random-pattern)
 162     ;; make sure (life-life-char) is used throughout
 163     (goto-char (point-min))
 164     (while (re-search-forward (life-not-void-regexp) nil t)
 165       (replace-match (life-life-string) t t))
 166     ;; center the pattern horizontally
 167     (goto-char (point-min))
 168     (setq n (/ (- fill-column (save-excursion (end-of-line) (point))) 2))
 169     (while (not (eobp))
 170       (indent-to n)
 171       (forward-line))
 172     ;; center the pattern vertically
 173     (setq n (/ (- (1- (window-height))
 174                   (count-lines (point-min) (point-max)))
 175                2))
 176     (goto-char (point-min))
 177     (newline n)
 178     (goto-char (point-max))
 179     (newline n)
 180     ;; pad lines out to fill-column
 181     (goto-char (point-min))
 182     (while (not (eobp))
 183       (end-of-line)
 184       (indent-to fill-column)
 185       (move-to-column fill-column)
 186       (delete-region (point) (progn (end-of-line) (point)))
 187       (forward-line))
 188     ;; expand tabs to spaces
 189     (untabify (point-min) (point-max))
 190     ;; before starting be sure the automaton has room to grow
 191     (life-expand-plane-if-needed)
 192     ;; compute initial neighbor deltas
 193     (life-compute-neighbor-deltas)))
 194
 195 (defun life-compute-neighbor-deltas ()
 196   (setq life-neighbor-deltas
 197         (list -1 (- fill-column)
 198               (- (1+ fill-column)) (- (+ 2 fill-column))
 199               1 fill-column (1+ fill-column)
 200               (+ 2 fill-column))))
 201
 202 (defun life-insert-random-pattern ()
 203   (insert-rectangle
 204    (elt life-patterns (random (length life-patterns))))
 205   (insert ?\n))
 206
 207 (defun life-increment-generation ()
 208   (life-increment life-current-generation)
 209   (setq life-generation-string (int-to-string life-current-generation)))
 210
 211 (defun life-grim-reaper ()
 212   ;; Clear the match information.  Later we check to see if it
 213   ;; is still clear, if so then all the cells have died.
 214   (set-match-data nil)
 215   (goto-char (point-min))
 216   ;; For speed declare all local variable outside the loop.
 217   (let (point char pivot living-neighbors list)
 218     (while (search-forward (life-life-string) nil t)
 219       (setq list life-neighbor-deltas
 220             living-neighbors 0
 221             pivot (1- (point)))
 222       (while list
 223         (setq point (+ pivot (car list))
 224               char (char-after point))
 225         (cond ((eq char (life-void-char))
 226                (subst-char-in-region point (1+ point)
 227                                      (life-void-char) 1 t))
 228               ((< char 3)
 229                (subst-char-in-region point (1+ point) char (1+ char) t))
 230               ((< char 9)
 231                (subst-char-in-region point (1+ point) char 9 t))
 232               ((>= char (life-life-char))
 233                (life-increment living-neighbors)))
 234         (setq list (cdr list)))
 235       (if (memq living-neighbors '(2 3))
 236           ()
 237         (subst-char-in-region pivot (1+ pivot)
 238                             (life-life-char) (life-death-char) t))))
 239   (if (null (match-beginning 0))
 240       (life-extinct-quit))
 241   (subst-char-in-region 1 (point-max) 9 (life-void-char) t)
 242   (subst-char-in-region 1 (point-max) 1 (life-void-char) t)
 243   (subst-char-in-region 1 (point-max) 2 (life-void-char) t)
 244   (subst-char-in-region 1 (point-max) (life-birth-char) (life-life-char) t)
 245   (subst-char-in-region 1 (point-max) (life-death-char) (life-void-char) t))
 246
 247 (defun life-expand-plane-if-needed ()
 248   (catch 'done
 249     (goto-char (point-min))
 250     (while (not (eobp))
 251       ;; check for life at beginning or end of line.  If found at
 252       ;; either end, expand at both ends,
 253       (cond ((or (eq (following-char) (life-life-char))
 254                  (eq (progn (end-of-line) (preceding-char)) (life-life-char)))
 255              (goto-char (point-min))
 256              (while (not (eobp))
 257                (insert (life-void-char))
 258                (end-of-line)
 259                (insert (life-void-char))
 260                (forward-char))
 261            (setq fill-column (+ 2 fill-column))
 262            (scroll-left 1)
 263            (life-compute-neighbor-deltas)
 264            (throw 'done t)))
 265       (forward-line)))
 266   (goto-char (point-min))
 267   ;; check for life within the first two lines of the buffer.
 268   ;; If present insert two lifeless lines at the beginning..
 269   (cond ((search-forward (life-life-string)
 270                          (+ (point) fill-column fill-column 2) t)
 271          (goto-char (point-min))
 272          (insert-char (life-void-char) fill-column)
 273          (insert ?\n)
 274          (insert-char (life-void-char) fill-column)
 275          (insert ?\n)
 276          (setq life-window-start (+ life-window-start fill-column 1))))
 277   (goto-char (point-max))
 278   ;; check for life within the last two lines of the buffer.
 279   ;; If present insert two lifeless lines at the end.
 280   (cond ((search-backward (life-life-string)
 281                           (- (point) fill-column fill-column 2) t)
 282          (goto-char (point-max))
 283          (insert-char (life-void-char) fill-column)
 284          (insert ?\n)
 285          (insert-char (life-void-char) fill-column)
 286          (insert ?\n)
 287          (setq life-window-start (+ life-window-start fill-column 1)))))
 288
 289 (defun life-display-generation (sleeptime)
 290   (goto-char life-window-start)
 291   (recenter 0)
 292
 293   ;; Redisplay; if the user has hit a key, exit the loop.
 294   (or (and (sit-for sleeptime) (< 0 sleeptime))
 295       (not (input-pending-p))
 296       (throw 'life-exit nil)))
 297
 298 (defun life-extinct-quit ()
 299   (life-display-generation 0)
 300   (signal 'life-extinct nil))
 301
 302 (put 'life-extinct 'error-conditions '(life-extinct quit))
 303 (put 'life-extinct 'error-message "All life has perished")
 304
 305 (provide 'life)
 306
 307 ;;; arch-tag: e9373544-755e-42f5-a9a1-4d4c422bb97a
 308 ;;; life.el ends here