1 ;;; life.el --- John Horton Conway's `Life' game for GNU Emacs
3 ;; Copyright (C) 1988, 2001-2011 Free Software Foundation, Inc.
5 ;; Author: Kyle Jones <kyleuunet.uu.net>
9 ;; This file is part of GNU Emacs.
11 ;; GNU Emacs is free software: you can redistribute it and/or modify
12 ;; it under the terms of the GNU General Public License as published by
13 ;; the Free Software Foundation, either version 3 of the License, or
14 ;; (at your option) any later version.
16 ;; GNU Emacs is distributed in the hope that it will be useful,
17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 ;; GNU General Public License for more details.
21 ;; You should have received a copy of the GNU General Public License
22 ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
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.
34 ("@@@ @@@" "@@ @@ " "@@@ @@@")
35 ("@@@ @@@" "@@ @@" "@@@ @@@")
36 ("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@")
43 ("@" "@" "@" "@" "@" "@" "@" "@" "@" "@" "@" "@" "@" "@" "@")
55 ("@@@@@@@@@" "@ @ @" "@ @@@@@ @" "@ @ @ @" "@@@ @@@"
56 "@ @ @ @" "@ @@@@@ @" "@ @ @" "@@@@@@@@@")
77 ("@@@@@@@@ @@@@@ @@@ @@@@@@@ @@@@@")]
78 "Vector of rectangles containing some Life startup patterns.")
80 ;; Macros are used macros for manifest constants instead of variables
81 ;; because the compiler will convert them to constants, which should
82 ;; eval faster than symbols.
84 ;; Don't change any of the life-* macro constants unless you thoroughly
85 ;; understand the `life-grim-reaper' function.
87 (defmacro life-life-char () ?@)
88 (defmacro life-death-char () (1+ (life-life-char)))
89 (defmacro life-birth-char () 3)
90 (defmacro life-void-char () ?\ )
92 (defmacro life-life-string () (char-to-string (life-life-char)))
93 (defmacro life-death-string () (char-to-string (life-death-char)))
94 (defmacro life-birth-string () (char-to-string (life-birth-char)))
95 (defmacro life-void-string () (char-to-string (life-void-char)))
96 (defmacro life-not-void-regexp () (concat "[^" (life-void-string) "\n]"))
98 (defmacro life-increment (variable) (list 'setq variable (list '1+ variable)))
101 ;; list of numbers that tell how many characters to move to get to
102 ;; each of a cell's eight neighbors.
103 (defvar life-neighbor-deltas nil)
105 ;; window display always starts here. Easier to deal with than
106 ;; (scroll-up) and (scroll-down) when trying to center the display.
107 (defvar life-window-start nil)
110 (defvar life-current-generation nil)
111 ;; Sadly, mode-line-format won't display numbers.
112 (defvar life-generation-string nil)
114 (defvar life-initialized nil
115 "Non-nil if `life' has been run at least once.")
118 (defun life (&optional sleeptime)
119 "Run Conway's Life simulation.
120 The starting pattern is randomly selected. Prefix arg (optional first
121 arg non-nil from a program) is the number of seconds to sleep between
122 generations (this defaults to 1)."
126 (setq life-initialized t)
127 (or sleeptime (setq sleeptime 1))
131 (let ((inhibit-quit t))
132 (life-display-generation sleeptime)
134 (life-expand-plane-if-needed)
135 (life-increment-generation)))))
137 (defalias 'life-mode 'life)
138 (put 'life-mode 'mode-class 'special)
142 (switch-to-buffer (get-buffer-create "*Life*") t)
144 (kill-all-local-variables)
145 (setq case-fold-search nil
147 major-mode 'life-mode
149 show-trailing-whitespace nil
150 life-current-generation 0
151 life-generation-string "0"
152 mode-line-buffer-identification '("Life: generation "
153 life-generation-string)
154 fill-column (1- (window-width))
156 (buffer-disable-undo (current-buffer))
157 ;; stuff in the random pattern
158 (life-insert-random-pattern)
159 ;; make sure (life-life-char) is used throughout
160 (goto-char (point-min))
161 (while (re-search-forward (life-not-void-regexp) nil t)
162 (replace-match (life-life-string) t t))
163 ;; center the pattern horizontally
164 (goto-char (point-min))
165 (setq n (/ (- fill-column (line-end-position)) 2))
169 ;; center the pattern vertically
170 (setq n (/ (- (1- (window-height))
171 (count-lines (point-min) (point-max)))
173 (goto-char (point-min))
175 (goto-char (point-max))
177 ;; pad lines out to fill-column
178 (goto-char (point-min))
181 (indent-to fill-column)
182 (move-to-column fill-column)
183 (delete-region (point) (progn (end-of-line) (point)))
185 ;; expand tabs to spaces
186 (untabify (point-min) (point-max))
187 ;; before starting be sure the automaton has room to grow
188 (life-expand-plane-if-needed)
189 ;; compute initial neighbor deltas
190 (life-compute-neighbor-deltas)))
192 (defun life-compute-neighbor-deltas ()
193 (setq life-neighbor-deltas
194 (list -1 (- fill-column)
195 (- (1+ fill-column)) (- (+ 2 fill-column))
196 1 fill-column (1+ fill-column)
199 (defun life-insert-random-pattern ()
201 (elt life-patterns (random (length life-patterns))))
204 (defun life-increment-generation ()
205 (life-increment life-current-generation)
206 (setq life-generation-string (int-to-string life-current-generation)))
208 (defun life-grim-reaper ()
209 ;; Clear the match information. Later we check to see if it
210 ;; is still clear, if so then all the cells have died.
212 (goto-char (point-min))
213 ;; For speed declare all local variable outside the loop.
214 (let (point char pivot living-neighbors list)
215 (while (search-forward (life-life-string) nil t)
216 (setq list life-neighbor-deltas
220 (setq point (+ pivot (car list))
221 char (char-after point))
222 (cond ((eq char (life-void-char))
223 (subst-char-in-region point (1+ point)
224 (life-void-char) 1 t))
226 (subst-char-in-region point (1+ point) char (1+ char) t))
228 (subst-char-in-region point (1+ point) char 9 t))
229 ((>= char (life-life-char))
230 (life-increment living-neighbors)))
231 (setq list (cdr list)))
232 (if (memq living-neighbors '(2 3))
234 (subst-char-in-region pivot (1+ pivot)
235 (life-life-char) (life-death-char) t))))
236 (if (null (match-beginning 0))
238 (subst-char-in-region 1 (point-max) 9 (life-void-char) t)
239 (subst-char-in-region 1 (point-max) 1 (life-void-char) t)
240 (subst-char-in-region 1 (point-max) 2 (life-void-char) t)
241 (subst-char-in-region 1 (point-max) (life-birth-char) (life-life-char) t)
242 (subst-char-in-region 1 (point-max) (life-death-char) (life-void-char) t))
244 (defun life-expand-plane-if-needed ()
246 (goto-char (point-min))
248 ;; check for life at beginning or end of line. If found at
249 ;; either end, expand at both ends,
250 (cond ((or (eq (following-char) (life-life-char))
251 (eq (progn (end-of-line) (preceding-char)) (life-life-char)))
252 (goto-char (point-min))
254 (insert (life-void-char))
256 (insert (life-void-char))
258 (setq fill-column (+ 2 fill-column))
260 (life-compute-neighbor-deltas)
263 (goto-char (point-min))
264 ;; check for life within the first two lines of the buffer.
265 ;; If present insert two lifeless lines at the beginning..
266 (cond ((search-forward (life-life-string)
267 (+ (point) fill-column fill-column 2) t)
268 (goto-char (point-min))
269 (insert-char (life-void-char) fill-column)
271 (insert-char (life-void-char) fill-column)
273 (setq life-window-start (+ life-window-start fill-column 1))))
274 (goto-char (point-max))
275 ;; check for life within the last two lines of the buffer.
276 ;; If present insert two lifeless lines at the end.
277 (cond ((search-backward (life-life-string)
278 (- (point) fill-column fill-column 2) t)
279 (goto-char (point-max))
280 (insert-char (life-void-char) fill-column)
282 (insert-char (life-void-char) fill-column)
284 (setq life-window-start (+ life-window-start fill-column 1)))))
286 (defun life-display-generation (sleeptime)
287 (goto-char life-window-start)
290 ;; Redisplay; if the user has hit a key, exit the loop.
291 (or (and (sit-for sleeptime) (< 0 sleeptime))
292 (not (input-pending-p))
293 (throw 'life-exit nil)))
295 (defun life-extinct-quit ()
296 (life-display-generation 0)
297 (signal 'life-extinct nil))
299 (put 'life-extinct 'error-conditions '(life-extinct quit))
300 (put 'life-extinct 'error-message "All life has perished")
304 ;;; life.el ends here