lisp/play/hanoi.el

   1 ;
   2 ; hanoi - towers of hanoi in GNUmacs
   3 ;
   4 ; Author (a) 1985, Damon Anton Permezel
   5 ;
   6
   7 ;;;
   8 ;;; hanoi-topos - direct cursor addressing
   9 ;;;
  10 (defun hanoi-topos (row col)
  11   (goto-line row)
  12   (beginning-of-line)
  13   (forward-char col))
  14
  15 ;;;
  16 ;;; hanoi - user callable Towers of Hanoi
  17 ;;;
  18 (defun hanoi (nrings)
  19   "Towers of Hanoi diversion.  Argument is number of rings."
  20   (interactive
  21    (list (if (null current-prefix-arg)
  22              3
  23              (prefix-numeric-value current-prefix-arg))))
  24   (if (<= nrings 0) (error "Negative number of rings"))
  25   (let (pole-spacing
  26         floor-row
  27         fly-row
  28         (window-height (window-height (selected-window)))
  29         (window-width (window-width (selected-window))))
  30     (let ((h (+ nrings 2))
  31           (w (+ (* (1- nrings) 6) 2 5)))
  32       (if (not (and (>= window-width h)
  33                     (> window-width w)))
  34           (progn
  35             (delete-other-windows)
  36             (if (not (and (>= (setq window-height
  37                                     (window-height (selected-window))) h)
  38                           (> (setq window-width
  39                                    (window-width (selected-window))) w)))
  40                 (error "Screen is too small (need at least %dx%d)" w h))))
  41       (setq pole-spacing (/ window-width 6))
  42       (if (not (zerop (logand pole-spacing 1)))
  43           ;; must be even
  44           (setq pole-spacing (1+ pole-spacing)))
  45       (setq floor-row (if (> (- window-height 3) h)
  46                           (- window-height 3) window-height)))
  47     (let ((fly-row (- floor-row nrings 1))
  48           ;; pole: column . fill height
  49           (pole-1 (cons pole-spacing floor-row))
  50           (pole-2 (cons (* 3 pole-spacing) floor-row))
  51           (pole-3 (cons (* 5 pole-spacing) floor-row))
  52           (rings (make-vector nrings nil)))
  53       ;; construct the ring list
  54       (let ((i 0))
  55         (while (< i nrings)
  56           ;; ring: [pole-number string empty-string]
  57           (aset rings i (vector nil
  58                                 (make-string (+ i i 3) (+ ?0 i))
  59                                 (make-string (+ i i 3) ?\  )))
  60           (setq i (1+ i))))
  61       ;;
  62       ;; init the screen
  63       ;;
  64       (switch-to-buffer "*Hanoi*")
  65       (setq buffer-read-only nil)
  66       (buffer-disable-undo (current-buffer))
  67       (erase-buffer)
  68       (let ((i 0))
  69         (while (< i floor-row)
  70           (setq i (1+ i))
  71           (insert-char ?\  (1- window-width))
  72           (insert ?\n)))
  73       (insert-char ?= (1- window-width))
  74
  75       (let ((n 1))
  76         (while (< n 6)
  77           (hanoi-topos fly-row (* n pole-spacing))
  78           (setq n (+ n 2))
  79           (let ((i fly-row))
  80             (while (< i floor-row)
  81               (setq i (1+ i))
  82               (next-line 1)
  83               (insert ?\|)
  84               (delete-char 1)
  85               (backward-char 1)))))
  86       ;(sit-for 0)
  87       ;;
  88       ;; now draw the rings in their initial positions
  89       ;;
  90       (let ((i 0)
  91             ring)
  92         (while (< i nrings)
  93           (setq ring (aref rings (- nrings 1 i)))
  94           (aset ring 0 (- floor-row i))
  95           (hanoi-topos (cdr pole-1)
  96                        (- (car pole-1) (- nrings i)))
  97           (hanoi-draw-ring ring t nil)
  98           (setcdr pole-1 (1- (cdr pole-1)))
  99           (setq i (1+ i))))
 100       (setq buffer-read-only t)
 101       (sit-for 0)
 102       ;;
 103       ;; do it!
 104       ;;
 105       (hanoi0 (1- nrings) pole-1 pole-2 pole-3)
 106       (goto-char (point-min))
 107       (message "Done")
 108       (setq buffer-read-only t)
 109       (set-buffer-modified-p (buffer-modified-p))
 110       (sit-for 0))))
 111
 112 ;;;
 113 ;;; hanoi0 - work horse of hanoi
 114 ;;;
 115 (defun hanoi0 (n from to work)
 116   (cond ((input-pending-p)
 117          (signal 'quit (list "I can tell you've had enough")))
 118         ((< n 0))
 119         (t
 120          (hanoi0 (1- n) from work to)
 121          (hanoi-move-ring n from to)
 122          (hanoi0 (1- n) work to from))))
 123
 124 ;;;
 125 ;;; hanoi-move-ring - move ring 'n' from 'from' to 'to'
 126 ;;;
 127 ;;;
 128 (defun hanoi-move-ring (n from to)
 129   (let ((ring (aref rings n))           ; ring <- ring: (ring# . row)
 130         (buffer-read-only nil))
 131     (let ((row (aref ring 0))           ; row <- row ring is on
 132           (col (- (car from) n 1))      ; col <- left edge of ring
 133           (dst-col (- (car to) n 1))    ; dst-col <- dest col for left edge
 134           (dst-row (cdr to)))           ; dst-row <- dest row for ring
 135       (hanoi-topos row col)
 136       (while (> row fly-row)            ; move up to the fly row
 137         (hanoi-draw-ring ring nil t)    ; blank out ring
 138         (previous-line 1)               ; move up a line
 139         (hanoi-draw-ring ring t nil)    ; redraw
 140         (sit-for 0)
 141         (setq row (1- row)))
 142       (setcdr from (1+ (cdr from)))     ; adjust top row
 143       ;;
 144       ;; fly the ring over to the right pole
 145       ;;
 146       (while (not (equal dst-col col))
 147         (cond ((> dst-col col)          ; dst-col > col: right shift
 148                (end-of-line 1)
 149                (delete-backward-char 2)
 150                (beginning-of-line 1)
 151                (insert ?\  ?\  )
 152                (sit-for 0)
 153                (setq col (1+ (1+ col))))
 154               ((< dst-col col)          ; dst-col < col: left shift
 155                (beginning-of-line 1)
 156                (delete-char 2)
 157                (end-of-line 1)
 158                (insert ?\  ?\  )
 159                (sit-for 0)
 160                (setq col (1- (1- col))))))
 161       ;;
 162       ;; let the ring float down
 163       ;;
 164       (hanoi-topos fly-row dst-col)
 165       (while (< row dst-row)            ; move down to the dest row
 166         (hanoi-draw-ring ring nil (> row fly-row)) ; blank out ring
 167         (next-line 1)                   ; move down a line
 168         (hanoi-draw-ring ring t nil)    ; redraw ring
 169         (sit-for 0)
 170         (setq row (1+ row)))
 171       (aset ring 0 dst-row)
 172       (setcdr to (1- (cdr to))))))      ; adjust top row
 173
 174 ;;;
 175 ;;; draw-ring - draw the ring at point, leave point unchanged
 176 ;;;
 177 ;;; Input:
 178 ;;;     ring
 179 ;;;     f1      -       flag: t -> draw, nil -> erase
 180 ;;;     f2      -       flag: t -> erasing and need to draw ?\|
 181 ;;;
 182 (defun hanoi-draw-ring (ring f1 f2)
 183   (save-excursion
 184     (let* ((string (if f1 (aref ring 1) (aref ring 2)))
 185            (len (length string)))
 186       (delete-char len)
 187       (insert string)
 188       (if f2
 189           (progn
 190             (backward-char (/ (+ len 1) 2))
 191             (delete-char 1) (insert ?\|))))))
 192