fixed error messages for create-world

collects/2htdp/private/world.rkt

@@ -37,17 +37,18 @@
 ;; -----------------------------------------------------------------------------
 ;; packages for broadcasting information to the universe 
 
-(define-struct package (world message) #:transparent)
-
-;; World Sexp -> Package 
-(define (create-package w m)
-  (check-arg 'make-package (sexp? m) 'sexp "second" m)
-  (make-package w m))
+(define-values (make-package package? package-world package-message)
+  (let ()
+    (struct package (world message) #:transparent)
+    (define (make-package w m)
+      (check-arg 'make-package (sexp? m) 'sexp "second" m)
+      (package w m))
+    (values make-package package? package-world package-message)))
 
 (provide
- (rename-out (create-package make-package)) ;; World S-expression -> Package
- package? ;; Any -> Package
- package-world
+ make-package  ;; World S-expression -> Package
+ package?      ;; Any -> Package
+ package-world ;; Package -> World 
  )
 
 (define world%

collects/2htdp/tests/error-messages.rkt

@@ -0,0 +1,16 @@
+#lang racket
+
+(require 2htdp/universe)
+
+(with-handlers ((exn:fail:contract? 
+                 (lambda (x) 
+                   (unless (regexp-match "make-package" (exn-message x))
+                     (raise x)))))
+  (make-package 1 2 3))
+
+(with-handlers ((exn:fail:contract? 
+                 (lambda (x) 
+                   (unless (regexp-match "make-bundle" (exn-message x))
+                     (raise x)))))
+  (make-bundle 1 2))
+

collects/2htdp/xtest

@@ -42,4 +42,4 @@ run name.rkt
 run pad1.rkt
 run pad1-handler.rkt
 run pad1-in-bsl.rkt
-
+run error-messages.rkt