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 <kyleuunet.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 the
  22 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  23 ;; Boston, MA 02111-1307, USA.
  24
  25 ;;; Commentary:
  26
  27 ;; A demonstrator for John Horton Conway's "Life" cellular automaton
  28 ;; in Emacs Lisp.  Picks a random one of a set of interesting Life
  29 ;; patterns and evolves it according to the familiar rules.
  30
  31 ;;; Code:
  32
  33 (defconst life-patterns
  34   [("@@@" " @@" "@@@")
  35    ("@@@ @@@" "@@  @@ " "@@@ @@@")
  36    ("@@@ @@@" "@@   @@" "@@@ @@@")
  37    ("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@")
  38    ("@@@@@@@@@@")
  39    ("   @@@@@@@@@@       "
  40     "     @@@@@@@@@@     "
  41     "       @@@@@@@@@@   "
  42     "@@@@@@@@@@          "
  43     "@@@@@@@@@@          ")
  44    ("@" "@" "@" "@" "@" "@" "@" "@" "@" "@" "@" "@" "@" "@" "@")
  45    ("@               @" "@               @"  "@               @"
  46     "@               @" "@               @"  "@               @"
  47     "@               @" "@               @"  "@               @"
  48     "@               @" "@               @"  "@               @"
  49     "@               @" "@               @"  "@               @")
  50    ("@@               " " @@              " "  @@             "
  51     "   @@            " "    @@           " "     @@          "
  52     "      @@         " "       @@        " "        @@       "
  53     "         @@      " "          @@     " "           @@    "
  54     "            @@   " "             @@  " "              @@ "
  55     "               @@")
  56    ("@@@@@@@@@" "@   @   @" "@ @@@@@ @" "@ @   @ @" "@@@   @@@"
  57     "@ @   @ @" "@ @@@@@ @" "@   @   @" "@@@@@@@@@")]
  58   "Vector of rectangles containing some Life startup patterns.")
  59
  60 ;; Macros are used macros for manifest constants instead of variables
  61 ;; because the compiler will convert them to constants, which should
  62 ;; eval faster than symbols.
  63 ;;
  64 ;; Don't change any of the life-* macro constants unless you thoroughly
  65 ;; understand the `life-grim-reaper' function.
  66
  67 (defmacro life-life-char () ?@)
  68 (defmacro life-death-char () (1+ (life-life-char)))
  69 (defmacro life-birth-char () 3)
  70 (defmacro life-void-char () ?\ )
  71
  72 (defmacro life-life-string () (char-to-string (life-life-char)))
  73 (defmacro life-death-string () (char-to-string (life-death-char)))
  74 (defmacro life-birth-string () (char-to-string (life-birth-char)))
  75 (defmacro life-void-string () (char-to-string (life-void-char)))
  76 (defmacro life-not-void-regexp () (concat "[^" (life-void-string) "\n]"))
  77
  78 (defmacro life-increment (variable) (list 'setq variable (list '1+ variable)))
  79
  80
  81 ;; list of numbers that tell how many characters to move to get to
  82 ;; each of a cell's eight neighbors.
  83 (defconst life-neighbor-deltas nil)
  84
  85 ;; window display always starts here.  Easier to deal with than
  86 ;; (scroll-up) and (scroll-down) when trying to center the display.
  87 (defconst life-window-start nil)
  88
  89 ;; For mode line
  90 (defconst life-current-generation nil)
  91 ;; Sadly, mode-line-format won't display numbers.
  92 (defconst life-generation-string nil)
  93
  94 (defvar life-initialized nil
  95   "Non-nil if `life' has been run at least once.")
  96
  97 ;;;###autoload
  98 (defun life (&optional sleeptime)
  99   "Run Conway's Life simulation.
 100 The starting pattern is randomly selected.  Prefix arg (optional first
 101 arg non-nil from a program) is the number of seconds to sleep between
 102 generations (this defaults to 1)."
 103   (interactive "p")
 104   (or life-initialized
 105       (random t))
 106   (setq life-initialized t)
 107   (or sleeptime (setq sleeptime 1))
 108   (life-setup)
 109   (life-display-generation sleeptime)
 110   (catch 'life-exit
 111     (while t
 112       (let ((inhibit-quit t))
 113         (life-grim-reaper)
 114         (life-expand-plane-if-needed)
 115         (life-increment-generation)
 116         (life-display-generation sleeptime)))))
 117
 118 (defalias 'life-mode 'life)
 119 (put 'life-mode 'mode-class 'special)
 120
 121 (defun life-setup ()
 122   (let (n)
 123     (switch-to-buffer (get-buffer-create "*Life*") t)
 124     (erase-buffer)
 125     (kill-all-local-variables)
 126     (setq case-fold-search nil
 127           mode-name "Life"
 128           major-mode 'life-mode
 129           truncate-lines t
 130           life-current-generation 0
 131           life-generation-string "0"
 132           mode-line-buffer-identification '("Life: generation "
 133                                             life-generation-string)
 134           fill-column (1- (window-width))
 135           life-window-start 1)
 136     (buffer-disable-undo (current-buffer))
 137     ;; stuff in the random pattern
 138     (life-insert-random-pattern)
 139     ;; make sure (life-life-char) is used throughout
 140     (goto-char (point-min))
 141     (while (re-search-forward (life-not-void-regexp) nil t)
 142       (replace-match (life-life-string) t t))
 143     ;; center the pattern horizontally
 144     (goto-char (point-min))
 145     (setq n (/ (- fill-column (save-excursion (end-of-line) (point))) 2))
 146     (while (not (eobp))
 147       (indent-to n)
 148       (forward-line))
 149     ;; center the pattern vertically
 150     (setq n (/ (- (1- (window-height))
 151                   (count-lines (point-min) (point-max)))
 152                2))
 153     (goto-char (point-min))
 154     (newline n)
 155     (goto-char (point-max))
 156     (newline n)
 157     ;; pad lines out to fill-column
 158     (goto-char (point-min))
 159     (while (not (eobp))
 160       (end-of-line)
 161       (indent-to fill-column)
 162       (move-to-column fill-column)
 163       (delete-region (point) (progn (end-of-line) (point)))
 164       (forward-line))
 165     ;; expand tabs to spaces
 166     (untabify (point-min) (point-max))
 167     ;; before starting be sure the automaton has room to grow
 168     (life-expand-plane-if-needed)
 169     ;; compute initial neighbor deltas
 170     (life-compute-neighbor-deltas)))
 171
 172 (defun life-compute-neighbor-deltas ()
 173   (setq life-neighbor-deltas
 174         (list -1 (- fill-column)
 175               (- (1+ fill-column)) (- (+ 2 fill-column))
 176               1 fill-column (1+ fill-column)
 177               (+ 2 fill-column))))
 178
 179 (defun life-insert-random-pattern ()
 180   (insert-rectangle
 181    (elt life-patterns (random (length life-patterns))))
 182   (insert ?\n))
 183
 184 (defun life-increment-generation ()
 185   (life-increment life-current-generation)
 186   (setq life-generation-string (int-to-string life-current-generation)))
 187
 188 (defun life-grim-reaper ()
 189   ;; Clear the match information.  Later we check to see if it
 190   ;; is still clear, if so then all the cells have died.
 191   (set-match-data nil)
 192   (goto-char (point-min))
 193   ;; For speed declare all local variable outside the loop.
 194   (let (point char pivot living-neighbors list)
 195     (while (search-forward (life-life-string) nil t)
 196       (setq list life-neighbor-deltas
 197             living-neighbors 0
 198             pivot (1- (point)))
 199       (while list
 200         (setq point (+ pivot (car list))
 201               char (char-after point))
 202         (cond ((eq char (life-void-char))
 203                (subst-char-in-region point (1+ point)
 204                                      (life-void-char) 1 t))
 205               ((< char 3)
 206                (subst-char-in-region point (1+ point) char (1+ char) t))
 207               ((< char 9)
 208                (subst-char-in-region point (1+ point) char 9 t))
 209               ((>= char (life-life-char))
 210                (life-increment living-neighbors)))
 211         (setq list (cdr list)))
 212       (if (memq living-neighbors '(2 3))
 213           ()
 214         (subst-char-in-region pivot (1+ pivot)
 215                             (life-life-char) (life-death-char) t))))
 216   (if (null (match-beginning 0))
 217       (life-extinct-quit))
 218   (subst-char-in-region 1 (point-max) 9 (life-void-char) t)
 219   (subst-char-in-region 1 (point-max) 1 (life-void-char) t)
 220   (subst-char-in-region 1 (point-max) 2 (life-void-char) t)
 221   (subst-char-in-region 1 (point-max) (life-birth-char) (life-life-char) t)
 222   (subst-char-in-region 1 (point-max) (life-death-char) (life-void-char) t))
 223
 224 (defun life-expand-plane-if-needed ()
 225   (catch 'done
 226     (goto-char (point-min))
 227     (while (not (eobp))
 228       ;; check for life at beginning or end of line.  If found at
 229       ;; either end, expand at both ends,
 230       (cond ((or (eq (following-char) (life-life-char))
 231                  (eq (progn (end-of-line) (preceding-char)) (life-life-char)))
 232              (goto-char (point-min))
 233              (while (not (eobp))
 234                (insert (life-void-char))
 235                (end-of-line)
 236                (insert (life-void-char))
 237                (forward-char))
 238            (setq fill-column (+ 2 fill-column))
 239            (scroll-left 1)
 240            (life-compute-neighbor-deltas)
 241            (throw 'done t)))
 242       (forward-line)))
 243   (goto-char (point-min))
 244   ;; check for life within the first two lines of the buffer.
 245   ;; If present insert two lifeless lines at the beginning..
 246   (cond ((search-forward (life-life-string)
 247                          (+ (point) fill-column fill-column 2) t)
 248          (goto-char (point-min))
 249          (insert-char (life-void-char) fill-column)
 250          (insert ?\n)
 251          (insert-char (life-void-char) fill-column)
 252          (insert ?\n)
 253          (setq life-window-start (+ life-window-start fill-column 1))))
 254   (goto-char (point-max))
 255   ;; check for life within the last two lines of the buffer.
 256   ;; If present insert two lifeless lines at the end.
 257   (cond ((search-backward (life-life-string)
 258                           (- (point) fill-column fill-column 2) t)
 259          (goto-char (point-max))
 260          (insert-char (life-void-char) fill-column)
 261          (insert ?\n)
 262          (insert-char (life-void-char) fill-column)
 263          (insert ?\n)
 264          (setq life-window-start (+ life-window-start fill-column 1)))))
 265
 266 (defun life-display-generation (sleeptime)
 267   (goto-char life-window-start)
 268   (recenter 0)
 269
 270   ;; Redisplay; if the user has hit a key, exit the loop.
 271   (or (eq t (sit-for sleeptime))
 272       (throw 'life-exit nil)))
 273
 274 (defun life-extinct-quit ()
 275   (life-display-generation 0)
 276   (signal 'life-extinct nil))
 277
 278 (put 'life-extinct 'error-conditions '(life-extinct quit))
 279 (put 'life-extinct 'error-message "All life has perished")
 280
 281 (provide 'life)
 282
 283 ;;; life.el ends here