lisp/play/life.el

   1 ;;; life.el --- John Horton Conway's `Life' game for GNU Emacs
   2
   3 ;; Copyright (C) 1988, 2001-2017 Free Software Foundation, Inc.
   4
   5 ;; Author: Kyle Jones <kyleuunet.uu.net>
   6 ;; Maintainer: emacs-devel@gnu.org
   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 <https://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 ;;;###autoload
 115 (defun life (&optional sleeptime)
 116   "Run Conway's Life simulation.
 117 The starting pattern is randomly selected.  Prefix arg (optional first
 118 arg non-nil from a program) is the number of seconds to sleep between
 119 generations (this defaults to 1)."
 120   (interactive "p")
 121   (or sleeptime (setq sleeptime 1))
 122   (life-setup)
 123   (catch 'life-exit
 124     (while t
 125       (let ((inhibit-quit t)
 126             (inhibit-read-only t))
 127         (life-display-generation sleeptime)
 128         (life-grim-reaper)
 129         (life-expand-plane-if-needed)
 130         (life-increment-generation)))))
 131
 132 (define-derived-mode life-mode special-mode "Life"
 133   "Major mode for the buffer of `life'."
 134   (setq-local case-fold-search nil)
 135   (setq-local truncate-lines t)
 136   (setq-local show-trailing-whitespace nil)
 137   (setq-local life-current-generation 0)
 138   (setq-local life-generation-string "0")
 139   (setq-local mode-line-buffer-identification '("Life: generation "
 140                                                 life-generation-string))
 141   (setq-local fill-column (1- (window-width)))
 142   (setq-local life-window-start 1)
 143   (buffer-disable-undo))
 144
 145 (defun life-setup ()
 146   (switch-to-buffer (get-buffer-create "*Life*") t)
 147   (erase-buffer)
 148   (life-mode)
 149   ;; stuff in the random pattern
 150   (let ((inhibit-read-only t))
 151     (life-insert-random-pattern)
 152     ;; make sure (life-life-char) is used throughout
 153     (goto-char (point-min))
 154     (while (re-search-forward (life-not-void-regexp) nil t)
 155       (replace-match (life-life-string) t t))
 156     ;; center the pattern horizontally
 157     (goto-char (point-min))
 158     (let ((n (/ (- fill-column (line-end-position)) 2)))
 159       (while (not (eobp))
 160         (indent-to n)
 161         (forward-line)))
 162     ;; center the pattern vertically
 163     (let ((n (/ (- (1- (window-height))
 164                    (count-lines (point-min) (point-max)))
 165                 2)))
 166       (goto-char (point-min))
 167       (newline n)
 168       (goto-char (point-max))
 169       (newline n))
 170     ;; pad lines out to fill-column
 171     (goto-char (point-min))
 172     (while (not (eobp))
 173       (end-of-line)
 174       (indent-to fill-column)
 175       (move-to-column fill-column)
 176       (delete-region (point) (progn (end-of-line) (point)))
 177       (forward-line))
 178     ;; expand tabs to spaces
 179     (untabify (point-min) (point-max))
 180     ;; before starting be sure the automaton has room to grow
 181     (life-expand-plane-if-needed)
 182     ;; compute initial neighbor deltas
 183     (life-compute-neighbor-deltas)))
 184
 185 (defun life-compute-neighbor-deltas ()
 186   (setq life-neighbor-deltas
 187         (list -1 (- fill-column)
 188               (- (1+ fill-column)) (- (+ 2 fill-column))
 189               1 fill-column (1+ fill-column)
 190               (+ 2 fill-column))))
 191
 192 (defun life-insert-random-pattern ()
 193   (insert-rectangle
 194    (elt life-patterns (random (length life-patterns))))
 195   (insert ?\n))
 196
 197 (defun life-increment-generation ()
 198   (life-increment life-current-generation)
 199   (setq life-generation-string (int-to-string life-current-generation)))
 200
 201 (defun life-grim-reaper ()
 202   ;; Clear the match information.  Later we check to see if it
 203   ;; is still clear, if so then all the cells have died.
 204   (set-match-data nil)
 205   (goto-char (point-min))
 206   ;; For speed declare all local variable outside the loop.
 207   (let (point char pivot living-neighbors list)
 208     (while (search-forward (life-life-string) nil t)
 209       (setq list life-neighbor-deltas
 210             living-neighbors 0
 211             pivot (1- (point)))
 212       (while list
 213         (setq point (+ pivot (car list))
 214               char (char-after point))
 215         (cond ((eq char (life-void-char))
 216                (subst-char-in-region point (1+ point)
 217                                      (life-void-char) 1 t))
 218               ((< char 3)
 219                (subst-char-in-region point (1+ point) char (1+ char) t))
 220               ((< char 9)
 221                (subst-char-in-region point (1+ point) char 9 t))
 222               ((>= char (life-life-char))
 223                (life-increment living-neighbors)))
 224         (setq list (cdr list)))
 225       (if (memq living-neighbors '(2 3))
 226           ()
 227         (subst-char-in-region pivot (1+ pivot)
 228                             (life-life-char) (life-death-char) t))))
 229   (if (null (match-beginning 0))
 230       (life-extinct-quit))
 231   (subst-char-in-region 1 (point-max) 9 (life-void-char) t)
 232   (subst-char-in-region 1 (point-max) 1 (life-void-char) t)
 233   (subst-char-in-region 1 (point-max) 2 (life-void-char) t)
 234   (subst-char-in-region 1 (point-max) (life-birth-char) (life-life-char) t)
 235   (subst-char-in-region 1 (point-max) (life-death-char) (life-void-char) t))
 236
 237 (defun life-expand-plane-if-needed ()
 238   (catch 'done
 239     (goto-char (point-min))
 240     (while (not (eobp))
 241       ;; check for life at beginning or end of line.  If found at
 242       ;; either end, expand at both ends,
 243       (cond ((or (eq (following-char) (life-life-char))
 244                  (eq (progn (end-of-line) (preceding-char)) (life-life-char)))
 245              (goto-char (point-min))
 246              (while (not (eobp))
 247                (insert (life-void-char))
 248                (end-of-line)
 249                (insert (life-void-char))
 250                (forward-char))
 251            (setq fill-column (+ 2 fill-column))
 252            (scroll-left 1)
 253            (life-compute-neighbor-deltas)
 254            (throw 'done t)))
 255       (forward-line)))
 256   (goto-char (point-min))
 257   ;; check for life within the first two lines of the buffer.
 258   ;; If present insert two lifeless lines at the beginning..
 259   (cond ((search-forward (life-life-string)
 260                          (+ (point) fill-column fill-column 2) t)
 261          (goto-char (point-min))
 262          (insert-char (life-void-char) fill-column)
 263          (insert ?\n)
 264          (insert-char (life-void-char) fill-column)
 265          (insert ?\n)
 266          (setq life-window-start (+ life-window-start fill-column 1))))
 267   (goto-char (point-max))
 268   ;; check for life within the last two lines of the buffer.
 269   ;; If present insert two lifeless lines at the end.
 270   (cond ((search-backward (life-life-string)
 271                           (- (point) fill-column fill-column 2) t)
 272          (goto-char (point-max))
 273          (insert-char (life-void-char) fill-column)
 274          (insert ?\n)
 275          (insert-char (life-void-char) fill-column)
 276          (insert ?\n)
 277          (setq life-window-start (+ life-window-start fill-column 1)))))
 278
 279 (defun life-display-generation (sleeptime)
 280   (goto-char life-window-start)
 281   (recenter 0)
 282
 283   ;; Redisplay; if the user has hit a key, exit the loop.
 284   (or (and (sit-for sleeptime) (< 0 sleeptime))
 285       (not (input-pending-p))
 286       (throw 'life-exit nil)))
 287
 288 (defun life-extinct-quit ()
 289   (life-display-generation 0)
 290   (signal 'life-extinct nil))
 291
 292 (define-error 'life-extinct "All life has perished" 'quit) ;FIXME: quit really?
 293
 294 (provide 'life)
 295
 296 ;;; life.el ends here