• Continue partners! Pick a new computer since we're in a new room.

Overview

• Preliminaries.
  • Admin.
  • Upcoming Work.
  • Extra Credit.
  • Questions.
• Lab.

Preliminaries

Admin

• Apologies for the bad design of this room.
• Thanks for finding the new classroom. We may be in this room tomorrow, too, depending on the state of the elevator.
• EG complained that I don't bring you enough food.
• DON'T ABUSE THE ART!
• Reminder: We've thrown a lot at you this semester.
  • At least 100 vocabulary terms
  • Some syntax
  • A variety of concepts - some explicit, some that come from your assignments
  • It's okay to ask questions, even on exams! I can choose whether or not to answer.
• Upcoming review sessions
  • Wednesday at 8pm (Zachary)
  • Thursday at 10am (Sam)
  • Thursday at 8pm (Caleb)

Upcoming Work

• Reading for Wednesday: Recursion Basics
  • Warning! For some, this will be even more confusing than section. For others, it will be intuitive. We will spend a few weeks trying to make it intuitive for everyone.
• HW 5 due tonight.
• Today's Lab writeup (due before class Friday)
  • Email to grader-151-01@cs.grinnell.edu
  • Subject: CSC 151 Lab Writeup Class 23 (Your Names)
  • Exercise:
• Exam 2 distributed.
  • We'll go through it quickly.
  • Probably lots of opportunities for corrections :-)

Extra Credit Opportunities

• If possible, send me these in advance.

Academic

• Any visit to the current show in the Faulconer gallery
• CS Table today: Barbie and the "Internet of Things"
• CS Extras Thursday: Blake Creasey on Watson

Peer Support

• Pals of PALS, pals@grinnell.edu, normally Saturday at 7:45 am (breakfast included), Sunday at 4:45, and Mondays at 4:45. Requires sign up in advance.
• Pun Club, Saturdays, 4pm, Way over Younker.

Other Good Things

• Friends of Drake Library book sale this weekend. Community room. Friday 5-8 pm. Saturday 8am-2pm. Admission $3 on Friday and $0 on Saturday. HC $1, PB $0.50. Books usually $1/box after some time on Saturday (noon?).

Questions

Should #2 work on any function?

Yes, those were just examples.

Does our procedure *have* to bound the y values?

No. You can assume a 100x200 window.

What's the difference between left and column?

left represents the left edge of an area. It's a column, but columns can take on other values.

When I'm picking the random column and row, what range should I choose from?

For the column, it should be a number between left and left+width-1.

But random only gives me a value between 0 and n-1.

Think about how to transform one range to another. (Hint: Addition.)

Do I need to document the procedures in part 3?

Yes. But you can use just 4P's.

Lab

• Important lesson 1: If you have something you think is a list, and you see a dot in the middle of it, it's not a list, and at some point things will probably break.

• Important lesson 2: car and cdr don't care whether or not it's a list, as long as it's created by cons (or is a non-empty list)

  • (car (cons a b)) = a
  • (cdr (cons a b)) = b

• Important lesson 3: Computer scientists usually count starting at 0 (for cardinal numbers)

  • The first element of a list is element 0
  • The second element of a list is element 1

• No writeup, but you need to make sure you understand this stuff. It's essential for the rest of the semester.