• Keep the same partners from the last class.
• Fruit!
• No handouts in the back of the room.

Overview

• Preliminaries.
  • Admin.
  • Upcoming Work.
  • Extra Credit.
  • Questions on algorithms.
  • Questions on Scheme readings
  • Quiz
• Lab.

Preliminaries

Admin

• Lots of preliminaries today!
• Evening tutor sessions start Sunday night.
• A purple sheet is going around the room to get interest in mentor session times.
• We keep hot water going 24/7 in the CS Commons for students in CS classes.
• The index cards in the back of the room are to support your note-taking systems.
  • I would recommend using the white cards for vocabulary.
  • I would recommend using one color for grammar (syntactic structures).
  • I would recomment using one color for algorithmic concepts.
  • You can think about how to use other colors.
  • Please be responsible in your consumption of the cards.
• In case you didn't know, you can submit questions anonymously via the "Submit Questions" link.
• No attendance today; the quizzes serve for attendance.
• I keep eboards for the review sessions, too. You can find links to them in the obvious places.
• I told you on Wednesday that I keep changing the number of key things that can go into algorithms. I realize that I left out one in our discussions: You need to rely on basic operations that the person or device carrying out the algorithm already knows.
• Since it's weekend, a few reminders.
  • Consider in advance what you want and what you feel comfortable with.
  • If you choose to partake, please partake responsibly.
  • Remember that consent is difficult to give or receive if you have been partaking.

Upcoming Work

• Lab writeup for lab 3, Problem 2. Due Monday (preferably before class, but as late as 10:30 p.m. is okay) http://bitly.com/151-2015S-lab03
• Assignment 2 distributed.
  
  • Due Tuesday at 10:30 p.m.
  • I have assigned partners for the assignment.
  • I will give you five minutes at the end of class to find those partners.
• Readings for Monday:
  • Symbolic Values
  • Numeric Values

Extra Credit Opportunities

Academic

Peer Support (Afternoon Section)

• Men's Baskeball, Saturday, 3 p.m., NewDarby
• Meditation group, Saturday, 4 p.m., CRSSJ
• Meditation group, Wednesday, 9:00 p.m., CRSSJ
• Swimming, Friday, January 30, 6:30 p.m., Osgood Natatorium
• Swimming, Saturday, January 31, noon, Osgood Natatorium
• Men's Tennis, Saturday, January 31, Field House

Recommended Events (no EC unless mentioned above)

• Women's Baskeball, Saturday, 1 p.m., NewDarby
• Belly Dance Club, to be scheduled
• Salsa Club, Tuesdays at 7pm and Sundays at 2pm
• #OneGrinnell, Wednesday, February 4 at 4:15 p.m.
• Economics talks, Spanish talks

Questions on Algorithms

How do we write an algorithm without formal experience?

You are sentient

You can use English

It's something I asked you to think about

How can I write an algorithm to add two numbers?

Teach someone to increment and decrement, and use repeated "increment first, decrement second"

Draw a line of length a inches, a subsequent line of length b inches, and measure the result.

Teach them to look it up in a table.

Teach them to use a calculator.

Questions on Scheme

In what order does Scheme evaluate things?

Inside out

If you have multiple expressions, evaluates them first to last.

If a procedure is arithmetical and takes more than two parameters, we often think about doing it left to right.

Do all the definitions have to be in the definitions pane and all the non-definitions in the interactions pane?

Custom, not requirement.

Quiz!

• When you finish the quiz, start the lab.

Lab

• I'll interrupt you with about five minutes to go so that you can find your homework partners.