►C211/  H211:   Introduction to Computer Science
▼Lectures
►Lecture 12:   Unlimited data
On this page:
1 Pre-flight check
2 Unlimited data
8.6.0.14
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Lecture 12: Unlimited data

This assignment is due on Tuesday, September 27 at 11:59pm. Submit it using Handin as assignment lecture12.

1 Pre-flight check

Are you ready? Click the button

Check your answer using “Show answer” above. Did you get it right? If not, click the button again to get another set, and keeping doing it until you get it right without peeking at the answer.

You don’t need to submit anything for this check. But the longer you put off mastering the skill of writing templates, the harder the rest of this entire course will be for you. If you want to do well in the course you have to stay on top of all the material. Don’t leave things to “learn later” because that’ll never work out. The first video of Lecture 11: More points recaps how to write templates (for processing unions). More details and exercises are found in

2 Unlimited data

; A Point is (make-point Number Number)
(define-struct point [x y])
 
; A BunchOfPoints is one of:
; - (make-none)
; - (make-some Point BunchOfPoints)
(define-struct none [])
(define-struct some [first rest])

Exercise 1. Define 3 examples of BunchOfPoints. Don’t use the examples from the video.

Exercise 2. Copy the comments below to your Definitions Window. For each of the 6 expressions, say whether it is a BunchOfPoints, and explain why not if not. The first 2 parts are already done for you; follow their pattern.
; 1. (make-some (make-point 1 1) (make-none))
;    is a BunchOfPoints
 
; 2. (make-point (make-some 1 1) (make-none))
;    is not a BunchOfPoints because it is a
;    use of neither make-some nor make-none
 
; 3. (make-some (make-point 70 40)
;               (make-point 30 50))
;
 
; 4. (make-none)
;
 
; 5. (make-some (make-point 30 50)
;               make-none)
;
 
; 6. (make-some
;     (make-point 70 40)
;     (make-some (make-point 30 50)
;                (make-none)))
;

Exercise 3. Here’s the first two steps of the design recipe for count-all-points.
; count-all-points : BunchOfPoints -> Number
; count how many points are in the bunch
(define (count-all-points bop) ...)
Write the template for count-all-points. Make it look like a function called process-bop, and do not put it in a comment.

Exercise 4. Finish designing count-all-points.

Exercise 5. Finish designing this function:
; move-points-up : BunchOfPoints -> BunchOfPoints
; subtract 1 from every Y coordinate
; in the given BunchOfPoints
 
(check-expect
 (move-points-up (make-none))
 (make-none))
 
(check-expect
 (move-points-up
  (make-some (make-point 30 50) (make-none)))
 (make-some (make-point 30 49) (make-none)))
 
(check-expect
 (move-points-up
  (make-some (make-point 70 40)
             (make-some (make-point 30 50) (make-none))))
 (make-some (make-point 70 39)
            (make-some (make-point 30 49) (make-none))))
 
(define (move-points-up bp) ...)

Exercise 6. Using the functions you’ve defined, and the mouse function defined in the video, run the big-bang animation shown.

Exercise 7. Optional: Change mouse to only add points when you click the mouse, as shown at the end of the video.

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