Complete Program from Figure 12

(define Basic-Shapes
  (unit (import) 
        (export Shape Rectangle Circle Translated)

    (define Shape (interface () draw))
    
    (define Rectangle
      (class* object% (Shape) (width height)
	(public
	  [draw (lambda (dc x y)
		  (send dc draw-rectangle x y width height))])
        (sequence (super-init))))
    
    (define Circle
      (class* object% (Shape) (radius)
	(public
	  [draw (lambda (dc x y)
		  (send dc draw-ellipse
			(- x radius)
			(- y radius)
			(* 2 radius)
			(* 2 radius)))])
        (sequence (super-init))))
    
    (define Translated
      (class* object% (Shape) (orig-shape dx dy)
	(public
	  [draw (lambda (dc x y)
		  (send orig-shape draw 
			dc (+ x dx) (+ y dy)))])
        (sequence (super-init))))))

(define Union-Shape
  (unit (import Shape)
        (export Union)

    (define Union
      (class* object% (Shape) (left right)
	(public
	  [draw (lambda (dc x y)
		  (send left draw dc x y)
		  (send right draw dc x y))])
        (sequence (super-init))))))

(define Basic+Union-Shapes 
  (compound-unit 
   (import)
   (link [S (Basic-Shapes)]
	 [US (Union-Shape (S Shape))])
   (export (S Shape)
           (S Rectangle)
           (S Circle)
           (S Translated)
           (US Union))))

(define BB-Shapes
  (unit (import Shape Rectangle Circle Translated Union) 
	(export BB-Shape BB-Rectangle BB-Circle 
		BB-Translated BB-Union
		make-BB BB-left BB-top BB-right BB-bottom)

    (define BB-Shape (interface (Shape) bounding-box))

    (define-struct BB (left top right bottom))
 
    (define BB-Rectangle
      (class* Rectangle (BB-Shape) (width height)
	(public
	  [bounding-box
	   (lambda () (make-BB 0 0 width height))])
	(sequence (super-init width height))))
        
    (define BB-Circle
      (class* Circle (BB-Shape) (r)
	(public
	  [bounding-box 
	   (lambda () (make-BB (- r) (- r) r r))])
	(sequence (super-init r))))
        
    (define BB-Translated
      (class* Translated (BB-Shape) (shape dx dy)
	(public
	  [bounding-box
	   (lambda ()
	     (let ([pre-bb (send shape bounding-box)])
	       (make-BB (+ (BB-left pre-bb) dx)
			(+ (BB-top pre-bb) dy)
			(+ (BB-right pre-bb) dx)
			(+ (BB-bottom pre-bb) dy))))])
	(sequence (super-init shape dx dy))))
        
    (define BB-Union
      (class* Union (BB-Shape) (left right)
	(public
	  [bounding-box
	   (lambda ()
	     (let ([left-bb (send left bounding-box)]
		   [right-bb (send right bounding-box)])
	       (make-BB (min (BB-left left-bb) (BB-left right-bb))
			(min (BB-top left-bb) (BB-top right-bb))
			(max (BB-right left-bb) (BB-right right-bb))
			(max (BB-bottom left-bb) (BB-bottom right-bb)))))])
	(sequence (super-init left right))))))

(define Basic+Union+BB-Shapes 
  (compound-unit
   (import)
   (link [S (Basic+Union-Shapes)] 
	 [BS (BB-Shapes (S Shape) 
			(S Rectangle) 
			(S Circle) 
			(S Translated) 
			(S Union))]) 
   (export (S Shape) 
	   (BS BB-Shape)

	   ;rename BS's BB-Rectangle to Rectangle, etc.:
	   (BS (BB-Rectangle Rectangle)) 
	   (BS (BB-Circle Circle)) 
	   (BS (BB-Translated Translated)) 
	   (BS (BB-Union Union))

	   (BS make-BB)
	   (BS BB-left)
	   (BS BB-top)
	   (BS BB-right)
	   (BS BB-bottom))))

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