New lab partners!

Overview

• Preliminaries.
  • Admin.
  • Upcoming Work.
  • Extra Credit.
  • Next Semester.
  • Academic Honesty.
  • Questions.
• About binary search trees.
• Lab.

Preliminaries

Admin

• Martin Dluhos's comment on "Spend less time on homework", explained. "Maybe that didn't come out quite the way I intended. What I meant to say is that not all the homework assigned is equally important and wanted to encourage them to think about what makes sense to spend time on for them."
• Yesterday's "debug the implementation" lab was complex. Let's chat about it quickly.
  • The "build a node constructor" was defective.
  • To make things more efficient, you cache the last node you looked at. But there's a flaw: If you insert twice, and aren't careful with insert, the cache can be incorrect.
    • Solution: Make sure you replace the value of the old one.
    • Solution: When you add something to the front, reset the cache.
  • Sam should add hints
• I will leave promptly at 11:50.

Upcoming Work

• Homework: Phase 1 of project (Class design, Algorithm design, I/O subsystem) due tomorrow.
• Reading for Wednesday: Tree Traversal
  • Walker says that his 301 students did not learn this well enough in my 207 class, so please pay careful attention.

Extra Credit

Academic

• Learning from Alums, today: Aru Singh '09
• CS Extras Thursday: Text Recognition in Maps
• CS Table Friday: One year after HealthCare.gov
• Learning from Alums, next Tuesday: Alex Cohn '11 (in person)
• CS Extras next Tuesday: Summer Opportunities in CS

Peer Support

• Ajuna's Radio show Mondays at 8pm. Listen to African music.
• Ezra's Radio show Thursdays at midnight. Radio melodrama.
• Charlie's Friday Night "War in Animated Film" ExCo.
• Copehagen, weekend of Nov. 20. 20th, 21st, 22nd at 7:30, 23rd at ???
• Basketball, Tonight, 7:30 p.m., Wartburg.
• Harry's Birthday Party Main 2nd. Please behave responsibly. Clergy will be present.

Miscellaneous

• VP Student Affairs Candidate Open Sessions
  • Wednesday, 4:15, JRC 209
  • Friday next, 4:15, JRC 209
• SHACS Open House, Today, 4-5pm. "If you have nay questions or concerns about the changes in SHACS, come to their open house."

Academic honesty (in 151)

The mistakes faculty made: One of the problems on exam 3 showed up on a lab that students did while taking the exam. Here's our solution.

(define turtle-polygon!
 (lambda (turtle side-length sides)
   (let ([angle (- 180 (/ (* 180 (- sides 2)) sides))])
     (repeat sides
             (lambda (turtle)
               (turtle-forward! turtle side-length)
               (turtle-turn! turtle angle))
             turtle))))

What would you do about a student who turned in an identical solution and did not cite ours?

Some data

• 6/30 used the longer formula. (There's a much more sensible (/ sides 360) formula.)
• 3/30 used (repeat sides (lambda (turtle) ...) turtle).

Preregistratation and department responses

• Overenrolled by 8 (and perhaps more) in security
• Overenrolled by 21 in HCI
• Overenrolled by 3 in 341
• Question for you: How many would take 321 if offered?
  • How many of those would take 322?

Questions

• I think I got all of yesterday's questions added to the EBoard.
• Addition: You could use the Wiki on your GitHub project for the non-code materials.

About binary search trees

• See board.

Lab

• Yes, it's a silly way to print trees. It's also a common one.