Tue Dec 1 22:34:42 1992 Jim Blandy (jimb@totoro.cs.oberlin.edu)

	* hanoi.el (hanoi): If pole-spacing is odd, round down, not up.
	To see if the window is wide enough, just check if one half of a
	ring will fit inside pole-spacing.

1 files changed, 31 insertions, 17 deletions

diff --git a/lisp/play/hanoi.el b/lisp/play/hanoi.el
index 65c5afe6e69..e65608235fd 100644
--- a/lisp/play/hanoi.el
+++ b/lisp/play/hanoi.el
@@ -29,26 +29,40 @@
              3
              (prefix-numeric-value current-prefix-arg))))  
   (if (<= nrings 0) (error "Negative number of rings"))
-  (let (pole-spacing
-        floor-row
-        fly-row
-        (window-height (window-height (selected-window)))
-        (window-width (window-width (selected-window))))
-    (let ((h (+ nrings 2))
-          (w (+ (* (1- nrings) 6) 2 5)))
-      (if (not (and (>= window-width h)
-                    (> window-width w)))
+  (let* (floor-row
+         fly-row
+         (window-height (window-height (selected-window)))
+         (window-width (window-width (selected-window)))
+
+         ;; This is the unit of spacing to use between poles.  It
+         ;; must be even.  We round down, since rounding up might
+         ;; cause us to draw off the edge of the window.
+         (pole-spacing (logand (/ window-width 6) (lognot 1))))
+    (let (
+          ;; The poles are (1+ NRINGS) rows high; we also want an
+          ;; empty row at the top for the flying rings, a base, and a
+          ;; blank line underneath that.
+          (h (+ nrings 4))
+
+          ;; If we have NRINGS rings, we label them with the numbers 0
+          ;; through NRINGS-1.  The width of ring i is 2i+3; it pokes
+          ;; out i spaces on either side of the pole.  Rather than
+          ;; checking if the window is wide enough to accomodate this,
+          ;; we make sure pole-spacing is large enough, since that
+          ;; works even when we have decremented pole-spacing to make
+          ;; it even.
+          (w (1+ nrings)))
+      (if (not (and (>= window-height h)
+                    (> pole-spacing w)))
           (progn
             (delete-other-windows)
             (if (not (and (>= (setq window-height
-                                    (window-height (selected-window))) h)
-                          (> (setq window-width
-                                   (window-width (selected-window))) w)))
+                                    (window-height (selected-window)))
+                              h)
+                          (> (setq pole-spacing
+                                   (logand (/ window-width 6) (lognot 1)))
+                             w)))
                 (error "Screen is too small (need at least %dx%d)" w h))))
-      (setq pole-spacing (/ window-width 6))
-      (if (not (zerop (logand pole-spacing 1)))
-          ;; must be even
-          (setq pole-spacing (1+ pole-spacing)))
       (setq floor-row (if (> (- window-height 3) h)
                           (- window-height 3) window-height)))
     (let ((fly-row (- floor-row nrings 1))
@@ -197,4 +211,4 @@
             (backward-char (/ (+ len 1) 2))
             (delete-char 1) (insert ?\|))))))
 
-;;; hanoi.el
\ No newline at end of file
+;;; hanoi.el