CSC151.01 2015S, Review Session 2: Starting Scheme
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_Overview_

* You ask questions, I attempt to answer.
* I ask questions, you attempt to answer.
* We look at some sample quiz questions.

_Admin_

* If you don't come to review sessions and count on other people to ask
  questions, you may not get your questions answered (particularly if
  no one shows up to review sessions).
* You can use review sessions as a time to sit and work on lab and ask
  me questions when they come up.

Your Questions
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My Questions
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Sample Quiz Questions
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### Question type one: "Draw the picture"

Consider the following sequence of definitions

        (define d1 (hshift-drawing 50 drawing-unit-circle))
        (define d2 (hshift-drawing 20 drawing-unit-square))
        (define d3 (scale-drawing 5 (drawing-group d1 d2)))
        (recolor-drawing d2 "red")
        (define d4 (scale-drawing 20 d1))
        (image-show (drawing->image (drawing-group d3 d4) 100 50))

Sketch the result

* Yes, we'll do something more sensible than that.
* Yes, we are often tricky and ask you to draw things that include off-canvas
  portions (which you should not draw)

### Question type two: "Compute this value"

The "simple geometric center" of a drawing is the point horizontally
midway between the left edge and the right edge of the drawing, and
vertically midway between the top edge and the bottom edge of the
drawing.  Recall that there is no `drawing-bottom` or `drawing-right`
procedure.  Sketch the code you would use to find the x coordinate of
the center of drawing `my-drawing`.  (You don't know the definition of
that drawing.)

    (define center-x
      (+ (/ (drawing-width my-drawing) 2)
         (drawing-left my-drawing)))