world with lang scheme

svn: r10331

collects/htdp/Test/world.ss

@@ -2,25 +2,19 @@
 ;; about the language level of this file in a form that our tools can easily process.
 #reader(lib "htdp-intermediate-lambda-reader.ss" "lang")((modname world) (read-case-sensitive #t) (teachpacks ((lib "world.ss" "teachpack" "htdp"))) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ((lib "world.ss" "teachpack" "htdp")))))
 ;; testing world
-
 ;; World = Nat
 
-(define world0 10)
+(define world0 100)
 
 (define (world->image w)
-  (place-image (circle 3 'solid 'red)
-               50 w
-               (empty-scene 100 100)))
+  (place-image (circle 3 'solid 'red) 50 w (empty-scene 100 100)))
 
-(define (world->next w) 
-  (if (>= (+ w 3) 100)
-      100
-      (+ w 1)))
+(define (world->next w) (sub1 w))
 
 (define (world->steer w ke)
   (cond
     [(char? ke) w]
-    [(symbol=? ke 'left) 10]
+    [(symbol=? ke 'left) 100]
     [(symbol=? ke 'right) 90]
     [else w]))
 
@@ -31,4 +25,4 @@
 (on-redraw world->image)
 (on-tick-event world->next)
 (on-key-event world->steer)
-(is-end-of-world (lambda (w) (= w 100)))
+(stop-when zero?)