lisp/play/life.el

   1 ;;; life.el --- John Horton Conway's `Life' game for GNU Emacs
   2
   3 ;; Copyright (C) 1988 Free Software Foundation, Inc.
   4
   5 ;; Author: Kyle Jones <talos!kjones@uunet.uu.net>
   6 ;; Keywords: games
   7
   8 ;; This file is part of GNU Emacs.
   9
  10 ;; GNU Emacs is free software; you can redistribute it and/or modify
  11 ;; it under the terms of the GNU General Public License as published by
  12 ;; the Free Software Foundation; either version 2, or (at your option)
  13 ;; any later version.
  14
  15 ;; GNU Emacs is distributed in the hope that it will be useful,
  16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ;; GNU General Public License for more details.
  19
  20 ;; You should have received a copy of the GNU General Public License
  21 ;; along with GNU Emacs; see the file COPYING.  If not, write to
  22 ;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  23
  24 ;;; Commentary:
  25
  26 ;; A demonstrator for John Horton Conway's "Life" cellular automaton
  27 ;; in Emacs Lisp.  Picks a random one of a set of interesting Life
  28 ;; patterns and evolves it according to the familiar rules.
  29
  30 ;;; Code:
  31
  32 (defconst life-patterns
  33   [("@@@" " @@" "@@@")
  34    ("@@@ @@@" "@@  @@ " "@@@ @@@")
  35    ("@@@ @@@" "@@   @@" "@@@ @@@")
  36    ("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@")
  37    ("@@@@@@@@@@")
  38    ("   @@@@@@@@@@       "
  39     "     @@@@@@@@@@     "
  40     "       @@@@@@@@@@   "
  41     "@@@@@@@@@@          "
  42     "@@@@@@@@@@          ")
  43    ("@" "@" "@" "@" "@" "@" "@" "@" "@" "@" "@" "@" "@" "@" "@")
  44    ("@               @" "@               @"  "@               @"
  45     "@               @" "@               @"  "@               @"
  46     "@               @" "@               @"  "@               @"
  47     "@               @" "@               @"  "@               @"
  48     "@               @" "@               @"  "@               @")
  49    ("@@               " " @@              " "  @@             "
  50     "   @@            " "    @@           " "     @@          "
  51     "      @@         " "       @@        " "        @@       "
  52     "         @@      " "          @@     " "           @@    "
  53     "            @@   " "             @@  " "              @@ "
  54     "               @@")
  55    ("@@@@@@@@@" "@   @   @" "@ @@@@@ @" "@ @   @ @" "@@@   @@@"
  56     "@ @   @ @" "@ @@@@@ @" "@   @   @" "@@@@@@@@@")]
  57   "Vector of rectangles containing some Life startup patterns.")
  58
  59 ;; Macros are used macros for manifest constants instead of variables
  60 ;; because the compiler will convert them to constants, which should
  61 ;; eval faster than symbols.
  62 ;;
  63 ;; Don't change any of the life-* macro constants unless you thoroughly
  64 ;; understand the `life-grim-reaper' function.
  65
  66 (defmacro life-life-char () ?@)
  67 (defmacro life-death-char () (1+ (life-life-char)))
  68 (defmacro life-birth-char () 3)
  69 (defmacro life-void-char () ?\ )
  70
  71 (defmacro life-life-string () (char-to-string (life-life-char)))
  72 (defmacro life-death-string () (char-to-string (life-death-char)))
  73 (defmacro life-birth-string () (char-to-string (life-birth-char)))
  74 (defmacro life-void-string () (char-to-string (life-void-char)))
  75 (defmacro life-not-void-regexp () (concat "[^" (life-void-string) "\n]"))
  76
  77 (defmacro life-increment (variable) (list 'setq variable (list '1+ variable)))
  78
  79
  80 ;; list of numbers that tell how many characters to move to get to
  81 ;; each of a cell's eight neighbors.
  82 (defconst life-neighbor-deltas nil)
  83
  84 ;; window display always starts here.  Easier to deal with than
  85 ;; (scroll-up) and (scroll-down) when trying to center the display.
  86 (defconst life-window-start nil)
  87
  88 ;; For mode line
  89 (defconst life-current-generation nil)
  90 ;; Sadly, mode-line-format won't display numbers.
  91 (defconst life-generation-string nil)
  92
  93 (defvar life-initialized nil
  94   "Non-nil if `life' has been run at least once.")
  95
  96 ;;;###autoload
  97 (defun life (&optional sleeptime)
  98   "Run Conway's Life simulation.
  99 The starting pattern is randomly selected.  Prefix arg (optional first
 100 arg non-nil from a program) is the number of seconds to sleep between
 101 generations (this defaults to 1)."
 102   (interactive "p")
 103   (or life-initialized
 104       (random t))
 105   (setq life-initialized t)
 106   (or sleeptime (setq sleeptime 1))
 107   (life-setup)
 108   (life-display-generation sleeptime)
 109   (catch 'life-exit
 110     (while t
 111       (let ((inhibit-quit t))
 112         (life-grim-reaper)
 113         (life-expand-plane-if-needed)
 114         (life-increment-generation)
 115         (life-display-generation sleeptime)))))
 116
 117 (defalias 'life-mode 'life)
 118 (put 'life-mode 'mode-class 'special)
 119
 120 (defun life-setup ()
 121   (let (n)
 122     (switch-to-buffer (get-buffer-create "*Life*") t)
 123     (erase-buffer)
 124     (kill-all-local-variables)
 125     (setq case-fold-search nil
 126           mode-name "Life"
 127           major-mode 'life-mode
 128           truncate-lines t
 129           life-current-generation 0
 130           life-generation-string "0"
 131           mode-line-buffer-identification '("Life: generation "
 132                                             life-generation-string)
 133           fill-column (1- (window-width))
 134           life-window-start 1)
 135     (buffer-disable-undo (current-buffer))
 136     ;; stuff in the random pattern
 137     (life-insert-random-pattern)
 138     ;; make sure (life-life-char) is used throughout
 139     (goto-char (point-min))
 140     (while (re-search-forward (life-not-void-regexp) nil t)
 141       (replace-match (life-life-string) t t))
 142     ;; center the pattern horizontally
 143     (goto-char (point-min))
 144     (setq n (/ (- fill-column (save-excursion (end-of-line) (point))) 2))
 145     (while (not (eobp))
 146       (indent-to n)
 147       (forward-line))
 148     ;; center the pattern vertically
 149     (setq n (/ (- (1- (window-height))
 150                   (count-lines (point-min) (point-max)))
 151                2))
 152     (goto-char (point-min))
 153     (newline n)
 154     (goto-char (point-max))
 155     (newline n)
 156     ;; pad lines out to fill-column
 157     (goto-char (point-min))
 158     (while (not (eobp))
 159       (end-of-line)
 160       (indent-to fill-column)
 161       (move-to-column fill-column)
 162       (delete-region (point) (progn (end-of-line) (point)))
 163       (forward-line))
 164     ;; expand tabs to spaces
 165     (untabify (point-min) (point-max))
 166     ;; before starting be sure the automaton has room to grow
 167     (life-expand-plane-if-needed)
 168     ;; compute initial neighbor deltas
 169     (life-compute-neighbor-deltas)))
 170
 171 (defun life-compute-neighbor-deltas ()
 172   (setq life-neighbor-deltas
 173         (list -1 (- fill-column)
 174               (- (1+ fill-column)) (- (+ 2 fill-column))
 175               1 fill-column (1+ fill-column)
 176               (+ 2 fill-column))))
 177
 178 (defun life-insert-random-pattern ()
 179   (insert-rectangle
 180    (elt life-patterns (random (length life-patterns))))
 181   (insert ?\n))
 182
 183 (defun life-increment-generation ()
 184   (life-increment life-current-generation)
 185   (setq life-generation-string (int-to-string life-current-generation)))
 186
 187 (defun life-grim-reaper ()
 188   ;; Clear the match information.  Later we check to see if it
 189   ;; is still clear, if so then all the cells have died.
 190   (store-match-data nil)
 191   (goto-char (point-min))
 192   ;; For speed declare all local variable outside the loop.
 193   (let (point char pivot living-neighbors list)
 194     (while (search-forward (life-life-string) nil t)
 195       (setq list life-neighbor-deltas
 196             living-neighbors 0
 197             pivot (1- (point)))
 198       (while list
 199         (setq point (+ pivot (car list))
 200               char (char-after point))
 201         (cond ((eq char (life-void-char))
 202                (subst-char-in-region point (1+ point)
 203                                      (life-void-char) 1 t))
 204               ((< char 3)
 205                (subst-char-in-region point (1+ point) char (1+ char) t))
 206               ((< char 9)
 207                (subst-char-in-region point (1+ point) char 9 t))
 208               ((>= char (life-life-char))
 209                (life-increment living-neighbors)))
 210         (setq list (cdr list)))
 211       (if (memq living-neighbors '(2 3))
 212           ()
 213         (subst-char-in-region pivot (1+ pivot)
 214                             (life-life-char) (life-death-char) t))))
 215   (if (null (match-beginning 0))
 216       (life-extinct-quit))
 217   (subst-char-in-region 1 (point-max) 9 (life-void-char) t)
 218   (subst-char-in-region 1 (point-max) 1 (life-void-char) t)
 219   (subst-char-in-region 1 (point-max) 2 (life-void-char) t)
 220   (subst-char-in-region 1 (point-max) (life-birth-char) (life-life-char) t)
 221   (subst-char-in-region 1 (point-max) (life-death-char) (life-void-char) t))
 222
 223 (defun life-expand-plane-if-needed ()
 224   (catch 'done
 225     (goto-char (point-min))
 226     (while (not (eobp))
 227       ;; check for life at beginning or end of line.  If found at
 228       ;; either end, expand at both ends,
 229       (cond ((or (eq (following-char) (life-life-char))
 230                  (eq (progn (end-of-line) (preceding-char)) (life-life-char)))
 231              (goto-char (point-min))
 232              (while (not (eobp))
 233                (insert (life-void-char))
 234                (end-of-line)
 235                (insert (life-void-char))
 236                (forward-char))
 237            (setq fill-column (+ 2 fill-column))
 238            (scroll-left 1)
 239            (life-compute-neighbor-deltas)
 240            (throw 'done t)))
 241       (forward-line)))
 242   (goto-char (point-min))
 243   ;; check for life within the first two lines of the buffer.
 244   ;; If present insert two lifeless lines at the beginning..
 245   (cond ((search-forward (life-life-string)
 246                          (+ (point) fill-column fill-column 2) t)
 247          (goto-char (point-min))
 248          (insert-char (life-void-char) fill-column)
 249          (insert ?\n)
 250          (insert-char (life-void-char) fill-column)
 251          (insert ?\n)
 252          (setq life-window-start (+ life-window-start fill-column 1))))
 253   (goto-char (point-max))
 254   ;; check for life within the last two lines of the buffer.
 255   ;; If present insert two lifeless lines at the end.
 256   (cond ((search-backward (life-life-string)
 257                           (- (point) fill-column fill-column 2) t)
 258          (goto-char (point-max))
 259          (insert-char (life-void-char) fill-column)
 260          (insert ?\n)
 261          (insert-char (life-void-char) fill-column)
 262          (insert ?\n)
 263          (setq life-window-start (+ life-window-start fill-column 1)))))
 264
 265 (defun life-display-generation (sleeptime)
 266   (goto-char life-window-start)
 267   (recenter 0)
 268
 269   ;; Redisplay; if the user has hit a key, exit the loop.
 270   (or (eq t (sit-for sleeptime))
 271       (throw 'life-exit nil)))
 272
 273 (defun life-extinct-quit ()
 274   (life-display-generation 0)
 275   (signal 'life-extinct nil))
 276
 277 (put 'life-extinct 'error-conditions '(life-extinct quit))
 278 (put 'life-extinct 'error-message "All life has perished")
 279
 280 (provide 'life)
 281
 282 ;;; life.el ends here