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, 2006, 2007, 2008, 2009, 2010, 2011 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 3 of the License, or
  15 ;; (at your option) 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.  If not, see <http://www.gnu.org/licenses/>.
  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 (defvar 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    ("                        @           "
  59     "                      @ @           "
  60     "            @@      @@            @@"
  61     "           @   @    @@            @@"
  62     "@@        @     @   @@              "
  63     "@@        @   @ @@    @ @           "
  64     "          @     @       @           "
  65     "           @   @                    "
  66     "            @@                      ")
  67    ("      @ "
  68     "    @ @@"
  69     "    @ @ "
  70     "    @   "
  71     "  @     "
  72     "@ @     ")
  73    ("@@@ @"
  74     "@    "
  75     "   @@"
  76     " @@ @"
  77     "@ @ @")
  78    ("@@@@@@@@ @@@@@   @@@      @@@@@@@ @@@@@")]
  79   "Vector of rectangles containing some Life startup patterns.")
  80
  81 ;; Macros are used macros for manifest constants instead of variables
  82 ;; because the compiler will convert them to constants, which should
  83 ;; eval faster than symbols.
  84 ;;
  85 ;; Don't change any of the life-* macro constants unless you thoroughly
  86 ;; understand the `life-grim-reaper' function.
  87
  88 (defmacro life-life-char () ?@)
  89 (defmacro life-death-char () (1+ (life-life-char)))
  90 (defmacro life-birth-char () 3)
  91 (defmacro life-void-char () ?\ )
  92
  93 (defmacro life-life-string () (char-to-string (life-life-char)))
  94 (defmacro life-death-string () (char-to-string (life-death-char)))
  95 (defmacro life-birth-string () (char-to-string (life-birth-char)))
  96 (defmacro life-void-string () (char-to-string (life-void-char)))
  97 (defmacro life-not-void-regexp () (concat "[^" (life-void-string) "\n]"))
  98
  99 (defmacro life-increment (variable) (list 'setq variable (list '1+ variable)))
 100
 101
 102 ;; list of numbers that tell how many characters to move to get to
 103 ;; each of a cell's eight neighbors.
 104 (defvar life-neighbor-deltas nil)
 105
 106 ;; window display always starts here.  Easier to deal with than
 107 ;; (scroll-up) and (scroll-down) when trying to center the display.
 108 (defvar life-window-start nil)
 109
 110 ;; For mode line
 111 (defvar life-current-generation nil)
 112 ;; Sadly, mode-line-format won't display numbers.
 113 (defvar life-generation-string nil)
 114
 115 (defvar life-initialized nil
 116   "Non-nil if `life' has been run at least once.")
 117
 118 ;;;###autoload
 119 (defun life (&optional sleeptime)
 120   "Run Conway's Life simulation.
 121 The starting pattern is randomly selected.  Prefix arg (optional first
 122 arg non-nil from a program) is the number of seconds to sleep between
 123 generations (this defaults to 1)."
 124   (interactive "p")
 125   (or life-initialized
 126       (random t))
 127   (setq life-initialized t)
 128   (or sleeptime (setq sleeptime 1))
 129   (life-setup)
 130   (catch 'life-exit
 131     (while t
 132       (let ((inhibit-quit t))
 133         (life-display-generation sleeptime)
 134         (life-grim-reaper)
 135         (life-expand-plane-if-needed)
 136         (life-increment-generation)))))
 137
 138 (defalias 'life-mode 'life)
 139 (put 'life-mode 'mode-class 'special)
 140
 141 (defun life-setup ()
 142   (let (n)
 143     (switch-to-buffer (get-buffer-create "*Life*") t)
 144     (erase-buffer)
 145     (kill-all-local-variables)
 146     (setq case-fold-search nil
 147           mode-name "Life"
 148           major-mode 'life-mode
 149           truncate-lines t
 150           show-trailing-whitespace nil
 151           life-current-generation 0
 152           life-generation-string "0"
 153           mode-line-buffer-identification '("Life: generation "
 154                                             life-generation-string)
 155           fill-column (1- (window-width))
 156           life-window-start 1)
 157     (buffer-disable-undo (current-buffer))
 158     ;; stuff in the random pattern
 159     (life-insert-random-pattern)
 160     ;; make sure (life-life-char) is used throughout
 161     (goto-char (point-min))
 162     (while (re-search-forward (life-not-void-regexp) nil t)
 163       (replace-match (life-life-string) t t))
 164     ;; center the pattern horizontally
 165     (goto-char (point-min))
 166     (setq n (/ (- fill-column (line-end-position)) 2))
 167     (while (not (eobp))
 168       (indent-to n)
 169       (forward-line))
 170     ;; center the pattern vertically
 171     (setq n (/ (- (1- (window-height))
 172                   (count-lines (point-min) (point-max)))
 173                2))
 174     (goto-char (point-min))
 175     (newline n)
 176     (goto-char (point-max))
 177     (newline n)
 178     ;; pad lines out to fill-column
 179     (goto-char (point-min))
 180     (while (not (eobp))
 181       (end-of-line)
 182       (indent-to fill-column)
 183       (move-to-column fill-column)
 184       (delete-region (point) (progn (end-of-line) (point)))
 185       (forward-line))
 186     ;; expand tabs to spaces
 187     (untabify (point-min) (point-max))
 188     ;; before starting be sure the automaton has room to grow
 189     (life-expand-plane-if-needed)
 190     ;; compute initial neighbor deltas
 191     (life-compute-neighbor-deltas)))
 192
 193 (defun life-compute-neighbor-deltas ()
 194   (setq life-neighbor-deltas
 195         (list -1 (- fill-column)
 196               (- (1+ fill-column)) (- (+ 2 fill-column))
 197               1 fill-column (1+ fill-column)
 198               (+ 2 fill-column))))
 199
 200 (defun life-insert-random-pattern ()
 201   (insert-rectangle
 202    (elt life-patterns (random (length life-patterns))))
 203   (insert ?\n))
 204
 205 (defun life-increment-generation ()
 206   (life-increment life-current-generation)
 207   (setq life-generation-string (int-to-string life-current-generation)))
 208
 209 (defun life-grim-reaper ()
 210   ;; Clear the match information.  Later we check to see if it
 211   ;; is still clear, if so then all the cells have died.
 212   (set-match-data nil)
 213   (goto-char (point-min))
 214   ;; For speed declare all local variable outside the loop.
 215   (let (point char pivot living-neighbors list)
 216     (while (search-forward (life-life-string) nil t)
 217       (setq list life-neighbor-deltas
 218             living-neighbors 0
 219             pivot (1- (point)))
 220       (while list
 221         (setq point (+ pivot (car list))
 222               char (char-after point))
 223         (cond ((eq char (life-void-char))
 224                (subst-char-in-region point (1+ point)
 225                                      (life-void-char) 1 t))
 226               ((< char 3)
 227                (subst-char-in-region point (1+ point) char (1+ char) t))
 228               ((< char 9)
 229                (subst-char-in-region point (1+ point) char 9 t))
 230               ((>= char (life-life-char))
 231                (life-increment living-neighbors)))
 232         (setq list (cdr list)))
 233       (if (memq living-neighbors '(2 3))
 234           ()
 235         (subst-char-in-region pivot (1+ pivot)
 236                             (life-life-char) (life-death-char) t))))
 237   (if (null (match-beginning 0))
 238       (life-extinct-quit))
 239   (subst-char-in-region 1 (point-max) 9 (life-void-char) t)
 240   (subst-char-in-region 1 (point-max) 1 (life-void-char) t)
 241   (subst-char-in-region 1 (point-max) 2 (life-void-char) t)
 242   (subst-char-in-region 1 (point-max) (life-birth-char) (life-life-char) t)
 243   (subst-char-in-region 1 (point-max) (life-death-char) (life-void-char) t))
 244
 245 (defun life-expand-plane-if-needed ()
 246   (catch 'done
 247     (goto-char (point-min))
 248     (while (not (eobp))
 249       ;; check for life at beginning or end of line.  If found at
 250       ;; either end, expand at both ends,
 251       (cond ((or (eq (following-char) (life-life-char))
 252                  (eq (progn (end-of-line) (preceding-char)) (life-life-char)))
 253              (goto-char (point-min))
 254              (while (not (eobp))
 255                (insert (life-void-char))
 256                (end-of-line)
 257                (insert (life-void-char))
 258                (forward-char))
 259            (setq fill-column (+ 2 fill-column))
 260            (scroll-left 1)
 261            (life-compute-neighbor-deltas)
 262            (throw 'done t)))
 263       (forward-line)))
 264   (goto-char (point-min))
 265   ;; check for life within the first two lines of the buffer.
 266   ;; If present insert two lifeless lines at the beginning..
 267   (cond ((search-forward (life-life-string)
 268                          (+ (point) fill-column fill-column 2) t)
 269          (goto-char (point-min))
 270          (insert-char (life-void-char) fill-column)
 271          (insert ?\n)
 272          (insert-char (life-void-char) fill-column)
 273          (insert ?\n)
 274          (setq life-window-start (+ life-window-start fill-column 1))))
 275   (goto-char (point-max))
 276   ;; check for life within the last two lines of the buffer.
 277   ;; If present insert two lifeless lines at the end.
 278   (cond ((search-backward (life-life-string)
 279                           (- (point) fill-column fill-column 2) t)
 280          (goto-char (point-max))
 281          (insert-char (life-void-char) fill-column)
 282          (insert ?\n)
 283          (insert-char (life-void-char) fill-column)
 284          (insert ?\n)
 285          (setq life-window-start (+ life-window-start fill-column 1)))))
 286
 287 (defun life-display-generation (sleeptime)
 288   (goto-char life-window-start)
 289   (recenter 0)
 290
 291   ;; Redisplay; if the user has hit a key, exit the loop.
 292   (or (and (sit-for sleeptime) (< 0 sleeptime))
 293       (not (input-pending-p))
 294       (throw 'life-exit nil)))
 295
 296 (defun life-extinct-quit ()
 297   (life-display-generation 0)
 298   (signal 'life-extinct nil))
 299
 300 (put 'life-extinct 'error-conditions '(life-extinct quit))
 301 (put 'life-extinct 'error-message "All life has perished")
 302
 303 (provide 'life)
 304
 305 ;;; life.el ends here