OOP with units and mixins

[Hassoun <hassoun@sympatico.ca>]

i am trying to learn Modular Object-Oriented Programming with Units and
Mixins, according to the excellent paper by R.B Findler and M. Flatt. 

i am using DrScheme v102 and i would like to implement the code in
graphical full scheme.

any hints about the necessary changes to apply on the following code
(taken from the paper's source):

;; special mumbo-jumbo to load in the MrEd library.
(require-library "debug.ss" "system")
(require-library "sig.ss" "mred")
(require-library "wxs.ss" "system")
(define MrEd-Toolkit
  (unit/sig->unit
   (compound-unit/sig
       (import)
     (link [C : mzlib:core^ ((require-library "corer.ss"))]
           [M : mred^ ((require-library "link.ss" "mred") C)])
     (export
      (var (M wx:pen%))
      (var (M wx:brush%))
      (var (M wx:const-solid))
      (var (M canvas%) mred:canvas%)
      (var (M frame%) mred:frame%)
      (var (M vertical-panel%) mred:vertical-panel%)))))

your help would be greatly appreciated
-- 
Hassoun Karam
hassoun@sympatico.ca
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