Code Outline (Functional Version), part 2 

      ;;; weight : Shape -> Number
      ;;; GIVEN: a shape
      ;;; RETURNS: the weight of the shape, assuming each shape
      ;;;     weighs 1 gram per pixel of area
      ;;; STRATEGY: use template for Shape on s
      
      (define (weight s)
        (cond ((my-circle? s)
               (my-circle-weight s))
              ((my-square? s)
               (my-square-weight s))
              ((my-composite? s)
               (my-composite-weight s))))
      
      ;;; add-to-scene : Shape Scene -> Scene
      ;;; RETURNS: a scene like the given one, but with the
      ;;;     given shape painted on it
      ;;; STRATEGY: use template for Shape on s
      
      (define (add-to-scene s scene)
        (cond ((my-circle? s)
               (my-circle-add-to-scene s scene))
              ((my-square? s)
               (my-square-add-to-scene s scene))
              ((my-composite? s)
               (my-composite-add-to-scene s scene))))

There are six small help functions left to write: