Overview

• Preliminaries.
  • Admin.
  • Questions.
• Additional images.
• Debriefing from image analysis.
• Students discuss programming techniques.
• Programming challenges.

Preliminaries

Admin

• Remember! You have a responsibility to cite all of the resources you use, even if you don't copy and paste.
• While you may be done with the formal work for CSC 151 Thursday evening, I expect you to show up for the remaining class periods.
• I won't be able to take notes and show off things simultaneously. Sorry.

Upcoming Work

• Homework for Thursday: Exam 3.
• Reading for Friday: Objects in Scheme
• No lab writeup.

Extra Credit

• CS Extra Thursday at 4:30 in Science 3821: Edward Snowden TED Talk.
• CS Table Friday at noon: Edward Snowden.
• Jazz band 7:30-9:30 Friday night in Sebring-Lewis.

Questions

Talk about the Moby Dick image.

• lowercase is turn
• UPPERCASE is forward

Do you need to see tests for the turtle draw text thingy?

No. I can read code.

• Where should I include examples
  • The ones that already include examples
  • The two vector problems

• Can you give us a hint about problem 9?

  (define husk
    (lambda (params)
      (cond
        [(fails-precondition-1 params)
         (error "Boy, that was bad input")]
        [(fails-precondition-2 params)
         (error "No, it shouldn't do that either)]
        [else
         (let kernel ([a 1]
                      [b 2])
           ...)])))
  

  or

  (define husk
    (lambda (parms)
      (let ([kernel (lambda (a b) ...)])
        (cond
          [(fails-precondition-1 params)
           (error "Boy, that was bad input")]
          [(fails-precondition-2 params)
           (error "No, it shouldn't do that either)]
          [else
           (kernel 1 2)]))))
  

Do we need a helper for problem 6?

You should not need a helper for probem 6.

For problem 3, can we use a recursive helper?

Not if you want to receive credit for the problem.

You will need to use map or repeat or for-each.

What is the goal in problem 3?

See the whiteboard

Can I do extra work and prevent a swap in problem 3 from using the same location?

Sure. But it will be harder.

What's the difference between problem 2 and problem 3?

Problem 2 swaps one pair of elements with specified indices.

Problem 3 swaps n pairs of elements with random indices. It probably uses your solution to problem 2.

What should I do if I can't solve problem 2?

Write problem 3 pretending that you correctly solved problem 3. But you won't be able to test.

Should we document tree-balanced? in problem 6?

Yes. The rule is "document unless told otherwise".

Additional images

Debriefing from image analysis

Students discuss programming techniques

Programming challenges