From c2211312546f0e60e8ba0903ec81fd21a71b1498 Mon Sep 17 00:00:00 2001
From: Matthias Felleisen <matthias@ccs.neu.edu>
Date: Thu, 15 Dec 2011 10:21:14 -0500
Subject: [PATCH] scheme/racket cleanup

---
 collects/2htdp/private/world.rkt          |  2 +-
 collects/2htdp/tests/universe-receive.rkt | 71 +++++++++++++++++++----
 2 files changed, 60 insertions(+), 13 deletions(-)

diff --git a/collects/2htdp/private/world.rkt b/collects/2htdp/private/world.rkt
index 6216029528..17fabecdc4 100644
--- a/collects/2htdp/private/world.rkt
+++ b/collects/2htdp/private/world.rkt
@@ -1,4 +1,4 @@
-#lang scheme/gui
+#lang racket/gui
 
 (require "check-aux.rkt"
          "timer.rkt"
diff --git a/collects/2htdp/tests/universe-receive.rkt b/collects/2htdp/tests/universe-receive.rkt
index c0b42861cf..35536d921c 100644
--- a/collects/2htdp/tests/universe-receive.rkt
+++ b/collects/2htdp/tests/universe-receive.rkt
@@ -1,15 +1,62 @@
-#lang racket
-
+;; The first three lines of this file were inserted by DrRacket. They record metadata
+;; 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 universe-receive) (read-case-sensitive #t) (teachpacks ()) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ())))
 (require 2htdp/universe)
 (require 2htdp/image)
 
-(launch-many-worlds
- (big-bang '*
-           (on-tick (lambda (w) w) 1/3 2)
-           (to-draw (λ (w) (empty-scene 200 200)))
-           (register LOCALHOST))
- 
- (universe '*
-           (on-tick (lambda (w) (make-bundle '* '() '())) 1/2 2)
-           (on-new (λ (u iw) (make-bundle '* (list (make-mail iw 'boo!)) '())))
-           (on-msg (λ (u iw msg) (make-bundle '* empty empty)))))
+;; Nat Nat ->* World1 World2 [Listof IWorld]
+;; launch a sending world, a receiving world, and a connecting universe
+(define (main rate limit)
+  (local (;; UniSt = [Listof IWorld]
+          
+          ;; UniSt IWorld -> UniSt 
+          (define (accept-another-world u iw)
+            (make-bundle (cons iw u) '() '()))
+          
+          ;; UniSt IWorld Message -> [bundle UniSt [List [Mail IWorld 'reset]] '()]
+          (define (forward-message u iw msg)
+            (make-bundle u (list (make-mail (other iw u) 'reset)) '()))
+          
+          ;; IWorld [List IWorld IWorld] -> IWorld 
+          ;; given one iworld, pick the other one from a list of two 
+          (define (other iw lo-iworld)
+            (if (iworld=? (first lo-iworld) iw)
+                (second lo-iworld)
+                (first lo-iworld))))
+    (launch-many-worlds 
+     (sending-world rate limit)
+     (receiving-world 10)
+     ;; a universe that channels all messages from one world to another
+     (universe '() (on-new accept-another-world) (on-msg forward-message)))))
+
+;; World1 = Number 
+
+;; Nat -> World1
+;; a world that counts down from n to 0, but resets to n for every message 
+(define (receiving-world n)
+  (local (;; World1 -> World1
+          (define (reset _1 _2) n))
+    (big-bang n
+              (on-tick sub1 1)
+              (to-draw (draw 'red))
+              (on-receive reset)
+              (stop-when zero?)
+              (register LOCALHOST))))
+
+;; World2 = Number 
+
+;; Number Number -> World2 
+;; a world that counts up to limit at rate r, sending a message at every tick
+(define (sending-world r l)
+  (local (;; World2 -> [package World2 Nat]
+          (define (inc w) (make-package (add1 w) w)))
+  (big-bang 0 (on-tick inc r l) (to-draw (draw 'blue)) (register LOCALHOST))))
+
+;; Color -> [Number -> Image]
+;; create an image for a number, in a fixed color c 
+(define (draw c)
+  (lambda (w) 
+    (overlay (text (number->string w) 22 c) (empty-scene 100 100))))
+
+;; run universe run 
+(main 1 3)
\ No newline at end of file