lisp/play/life.el

   1 ;;; life.el --- John Horton Conway's `Life' game for GNU Emacs
   2
   3 ;; Copyright (C) 1988, 2001-2012  Free Software Foundation, Inc.
   4
   5 ;; Author: Kyle Jones <kyleuunet.uu.net>
   6 ;; Maintainer: FSF
   7 ;; Keywords: games
   8
   9 ;; This file is part of GNU Emacs.
  10
  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.
  15
  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.
  20
  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/>.
  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 (defvar 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    ("                        @           "
  58     "                      @ @           "
  59     "            @@      @@            @@"
  60     "           @   @    @@            @@"
  61     "@@        @     @   @@              "
  62     "@@        @   @ @@    @ @           "
  63     "          @     @       @           "
  64     "           @   @                    "
  65     "            @@                      ")
  66    ("      @ "
  67     "    @ @@"
  68     "    @ @ "
  69     "    @   "
  70     "  @     "
  71     "@ @     ")
  72    ("@@@ @"
  73     "@    "
  74     "   @@"
  75     " @@ @"
  76     "@ @ @")
  77    ("@@@@@@@@ @@@@@   @@@      @@@@@@@ @@@@@")]
  78   "Vector of rectangles containing some Life startup patterns.")
  79
  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.
  83 ;;
  84 ;; Don't change any of the life-* macro constants unless you thoroughly
  85 ;; understand the `life-grim-reaper' function.
  86
  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 () ?\ )
  91
  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]"))
  97
  98 (defmacro life-increment (variable) (list 'setq variable (list '1+ variable)))
  99
 100
 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)
 104
 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)
 108
 109 ;; For mode line
 110 (defvar life-current-generation nil)
 111 ;; Sadly, mode-line-format won't display numbers.
 112 (defvar life-generation-string nil)
 113
 114 (defvar life-initialized nil
 115   "Non-nil if `life' has been run at least once.")
 116
 117 ;;;###autoload
 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)."
 123   (interactive "p")
 124   (or life-initialized
 125       (random t))
 126   (setq life-initialized t)
 127   (or sleeptime (setq sleeptime 1))
 128   (life-setup)
 129   (catch 'life-exit
 130     (while t
 131       (let ((inhibit-quit t))
 132         (life-display-generation sleeptime)
 133         (life-grim-reaper)
 134         (life-expand-plane-if-needed)
 135         (life-increment-generation)))))
 136
 137 (defalias 'life-mode 'life)
 138 (put 'life-mode 'mode-class 'special)
 139
 140 (defun life-setup ()
 141   (let (n)
 142     (switch-to-buffer (get-buffer-create "*Life*") t)
 143     (erase-buffer)
 144     (kill-all-local-variables)
 145     (setq case-fold-search nil
 146           mode-name "Life"
 147           major-mode 'life-mode
 148           truncate-lines t
 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))
 155           life-window-start 1)
 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))
 166     (while (not (eobp))
 167       (indent-to n)
 168       (forward-line))
 169     ;; center the pattern vertically
 170     (setq n (/ (- (1- (window-height))
 171                   (count-lines (point-min) (point-max)))
 172                2))
 173     (goto-char (point-min))
 174     (newline n)
 175     (goto-char (point-max))
 176     (newline n)
 177     ;; pad lines out to fill-column
 178     (goto-char (point-min))
 179     (while (not (eobp))
 180       (end-of-line)
 181       (indent-to fill-column)
 182       (move-to-column fill-column)
 183       (delete-region (point) (progn (end-of-line) (point)))
 184       (forward-line))
 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)))
 191
 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)
 197               (+ 2 fill-column))))
 198
 199 (defun life-insert-random-pattern ()
 200   (insert-rectangle
 201    (elt life-patterns (random (length life-patterns))))
 202   (insert ?\n))
 203
 204 (defun life-increment-generation ()
 205   (life-increment life-current-generation)
 206   (setq life-generation-string (int-to-string life-current-generation)))
 207
 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.
 211   (set-match-data nil)
 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
 217             living-neighbors 0
 218             pivot (1- (point)))
 219       (while list
 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))
 225               ((< char 3)
 226                (subst-char-in-region point (1+ point) char (1+ char) t))
 227               ((< char 9)
 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))
 233           ()
 234         (subst-char-in-region pivot (1+ pivot)
 235                             (life-life-char) (life-death-char) t))))
 236   (if (null (match-beginning 0))
 237       (life-extinct-quit))
 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))
 243
 244 (defun life-expand-plane-if-needed ()
 245   (catch 'done
 246     (goto-char (point-min))
 247     (while (not (eobp))
 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))
 253              (while (not (eobp))
 254                (insert (life-void-char))
 255                (end-of-line)
 256                (insert (life-void-char))
 257                (forward-char))
 258            (setq fill-column (+ 2 fill-column))
 259            (scroll-left 1)
 260            (life-compute-neighbor-deltas)
 261            (throw 'done t)))
 262       (forward-line)))
 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)
 270          (insert ?\n)
 271          (insert-char (life-void-char) fill-column)
 272          (insert ?\n)
 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)
 281          (insert ?\n)
 282          (insert-char (life-void-char) fill-column)
 283          (insert ?\n)
 284          (setq life-window-start (+ life-window-start fill-column 1)))))
 285
 286 (defun life-display-generation (sleeptime)
 287   (goto-char life-window-start)
 288   (recenter 0)
 289
 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)))
 294
 295 (defun life-extinct-quit ()
 296   (life-display-generation 0)
 297   (signal 'life-extinct nil))
 298
 299 (put 'life-extinct 'error-conditions '(life-extinct quit))
 300 (put 'life-extinct 'error-message "All life has perished")
 301
 302 (provide 'life)
 303
 304 ;;; life.el ends here