code.delx.au - gnu-emacs/blob - 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 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 2, 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   "Vector of rectangles containing some Life startup patterns.")
  61
  62 ;; Macros are used macros for manifest constants instead of variables
  63 ;; because the compiler will convert them to constants, which should
  64 ;; eval faster than symbols.
  65 ;;
  66 ;; Don't change any of the life-* macro constants unless you thoroughly
  67 ;; understand the `life-grim-reaper' function.
  68
  69 (defmacro life-life-char () ?@)
  70 (defmacro life-death-char () (1+ (life-life-char)))
  71 (defmacro life-birth-char () 3)
  72 (defmacro life-void-char () ?\ )
  73
  74 (defmacro life-life-string () (char-to-string (life-life-char)))
  75 (defmacro life-death-string () (char-to-string (life-death-char)))
  76 (defmacro life-birth-string () (char-to-string (life-birth-char)))
  77 (defmacro life-void-string () (char-to-string (life-void-char)))
  78 (defmacro life-not-void-regexp () (concat "[^" (life-void-string) "\n]"))
  79
  80 (defmacro life-increment (variable) (list 'setq variable (list '1+ variable)))
  81
  82
  83 ;; list of numbers that tell how many characters to move to get to
  84 ;; each of a cell's eight neighbors.
  85 (defvar life-neighbor-deltas nil)
  86
  87 ;; window display always starts here.  Easier to deal with than
  88 ;; (scroll-up) and (scroll-down) when trying to center the display.
  89 (defvar life-window-start nil)
  90
  91 ;; For mode line
  92 (defvar life-current-generation nil)
  93 ;; Sadly, mode-line-format won't display numbers.
  94 (defvar life-generation-string nil)
  95
  96 (defvar life-initialized nil
  97   "Non-nil if `life' has been run at least once.")
  98
  99 ;;;###autoload
 100 (defun life (&optional sleeptime)
 101   "Run Conway's Life simulation.
 102 The starting pattern is randomly selected.  Prefix arg (optional first
 103 arg non-nil from a program) is the number of seconds to sleep between
 104 generations (this defaults to 1)."
 105   (interactive "p")
 106   (or life-initialized
 107       (random t))
 108   (setq life-initialized t)
 109   (or sleeptime (setq sleeptime 1))
 110   (life-setup)
 111   (catch 'life-exit
 112     (while t
 113       (let ((inhibit-quit t))
 114         (life-display-generation sleeptime)
 115         (life-grim-reaper)
 116         (life-expand-plane-if-needed)
 117         (life-increment-generation)))))
 118
 119 (defalias 'life-mode 'life)
 120 (put 'life-mode 'mode-class 'special)
 121
 122 (defun life-setup ()
 123   (let (n)
 124     (switch-to-buffer (get-buffer-create "*Life*") t)
 125     (erase-buffer)
 126     (kill-all-local-variables)
 127     (setq case-fold-search nil
 128           mode-name "Life"
 129           major-mode 'life-mode
 130           truncate-lines t
 131           life-current-generation 0
 132           life-generation-string "0"
 133           mode-line-buffer-identification '("Life: generation "
 134                                             life-generation-string)
 135           fill-column (1- (window-width))
 136           life-window-start 1)
 137     (buffer-disable-undo (current-buffer))
 138     ;; stuff in the random pattern
 139     (life-insert-random-pattern)
 140     ;; make sure (life-life-char) is used throughout
 141     (goto-char (point-min))
 142     (while (re-search-forward (life-not-void-regexp) nil t)
 143       (replace-match (life-life-string) t t))
 144     ;; center the pattern horizontally
 145     (goto-char (point-min))
 146     (setq n (/ (- fill-column (save-excursion (end-of-line) (point))) 2))
 147     (while (not (eobp))
 148       (indent-to n)
 149       (forward-line))
 150     ;; center the pattern vertically
 151     (setq n (/ (- (1- (window-height))
 152                   (count-lines (point-min) (point-max)))
 153                2))
 154     (goto-char (point-min))
 155     (newline n)
 156     (goto-char (point-max))
 157     (newline n)
 158     ;; pad lines out to fill-column
 159     (goto-char (point-min))
 160     (while (not (eobp))
 161       (end-of-line)
 162       (indent-to fill-column)
 163       (move-to-column fill-column)
 164       (delete-region (point) (progn (end-of-line) (point)))
 165       (forward-line))
 166     ;; expand tabs to spaces
 167     (untabify (point-min) (point-max))
 168     ;; before starting be sure the automaton has room to grow
 169     (life-expand-plane-if-needed)
 170     ;; compute initial neighbor deltas
 171     (life-compute-neighbor-deltas)))
 172
 173 (defun life-compute-neighbor-deltas ()
 174   (setq life-neighbor-deltas
 175         (list -1 (- fill-column)
 176               (- (1+ fill-column)) (- (+ 2 fill-column))
 177               1 fill-column (1+ fill-column)
 178               (+ 2 fill-column))))
 179
 180 (defun life-insert-random-pattern ()
 181   (insert-rectangle
 182    (elt life-patterns (random (length life-patterns))))
 183   (insert ?\n))
 184
 185 (defun life-increment-generation ()
 186   (life-increment life-current-generation)
 187   (setq life-generation-string (int-to-string life-current-generation)))
 188
 189 (defun life-grim-reaper ()
 190   ;; Clear the match information.  Later we check to see if it
 191   ;; is still clear, if so then all the cells have died.
 192   (set-match-data nil)
 193   (goto-char (point-min))
 194   ;; For speed declare all local variable outside the loop.
 195   (let (point char pivot living-neighbors list)
 196     (while (search-forward (life-life-string) nil t)
 197       (setq list life-neighbor-deltas
 198             living-neighbors 0
 199             pivot (1- (point)))
 200       (while list
 201         (setq point (+ pivot (car list))
 202               char (char-after point))
 203         (cond ((eq char (life-void-char))
 204                (subst-char-in-region point (1+ point)
 205                                      (life-void-char) 1 t))
 206               ((< char 3)
 207                (subst-char-in-region point (1+ point) char (1+ char) t))
 208               ((< char 9)
 209                (subst-char-in-region point (1+ point) char 9 t))
 210               ((>= char (life-life-char))
 211                (life-increment living-neighbors)))
 212         (setq list (cdr list)))
 213       (if (memq living-neighbors '(2 3))
 214           ()
 215         (subst-char-in-region pivot (1+ pivot)
 216                             (life-life-char) (life-death-char) t))))
 217   (if (null (match-beginning 0))
 218       (life-extinct-quit))
 219   (subst-char-in-region 1 (point-max) 9 (life-void-char) t)
 220   (subst-char-in-region 1 (point-max) 1 (life-void-char) t)
 221   (subst-char-in-region 1 (point-max) 2 (life-void-char) t)
 222   (subst-char-in-region 1 (point-max) (life-birth-char) (life-life-char) t)
 223   (subst-char-in-region 1 (point-max) (life-death-char) (life-void-char) t))
 224
 225 (defun life-expand-plane-if-needed ()
 226   (catch 'done
 227     (goto-char (point-min))
 228     (while (not (eobp))
 229       ;; check for life at beginning or end of line.  If found at
 230       ;; either end, expand at both ends,
 231       (cond ((or (eq (following-char) (life-life-char))
 232                  (eq (progn (end-of-line) (preceding-char)) (life-life-char)))
 233              (goto-char (point-min))
 234              (while (not (eobp))
 235                (insert (life-void-char))
 236                (end-of-line)
 237                (insert (life-void-char))
 238                (forward-char))
 239            (setq fill-column (+ 2 fill-column))
 240            (scroll-left 1)
 241            (life-compute-neighbor-deltas)
 242            (throw 'done t)))
 243       (forward-line)))
 244   (goto-char (point-min))
 245   ;; check for life within the first two lines of the buffer.
 246   ;; If present insert two lifeless lines at the beginning..
 247   (cond ((search-forward (life-life-string)
 248                          (+ (point) fill-column fill-column 2) t)
 249          (goto-char (point-min))
 250          (insert-char (life-void-char) fill-column)
 251          (insert ?\n)
 252          (insert-char (life-void-char) fill-column)
 253          (insert ?\n)
 254          (setq life-window-start (+ life-window-start fill-column 1))))
 255   (goto-char (point-max))
 256   ;; check for life within the last two lines of the buffer.
 257   ;; If present insert two lifeless lines at the end.
 258   (cond ((search-backward (life-life-string)
 259                           (- (point) fill-column fill-column 2) t)
 260          (goto-char (point-max))
 261          (insert-char (life-void-char) fill-column)
 262          (insert ?\n)
 263          (insert-char (life-void-char) fill-column)
 264          (insert ?\n)
 265          (setq life-window-start (+ life-window-start fill-column 1)))))
 266
 267 (defun life-display-generation (sleeptime)
 268   (goto-char life-window-start)
 269   (recenter 0)
 270
 271   ;; Redisplay; if the user has hit a key, exit the loop.
 272   (or (eq t (sit-for sleeptime))
 273       (throw 'life-exit nil)))
 274
 275 (defun life-extinct-quit ()
 276   (life-display-generation 0)
 277   (signal 'life-extinct nil))
 278
 279 (put 'life-extinct 'error-conditions '(life-extinct quit))
 280 (put 'life-extinct 'error-message "All life has perished")
 281
 282 (provide 'life)
 283
 284 ;;; arch-tag: e9373544-755e-42f5-a9a1-4d4c422bb97a
 285 ;;; life.el ends here