Overview

• Preliminaries.
  • Admin.
  • Upcoming Work.
  • Extra Credit.
  • Questions.
• Important learning outcomes from Friday's class.
• Important/strange concepts from today.
  • Composition
  • Lambda expressions
• Lab

Preliminaries

Admin

• New partners!
• Mentor session Monday at 7:00 p.m.
• Just in case it's not clear: If I find that you have posted your exam work online, including via social media, I will report you for ethical violations and, unless prevented by College policy, will fail you in the class.
• Friday the 13th falls on Friday next month. Be careful.
• Exam 1 to be returned tomorrow.
• Congrats to all of our athletes who competed this weekend.
• We'll do a quick debrief on some learning outcomes from Friday's class.
  • An overview of logic ... understanding these things through logic and not just programming is useful.
  • A different approach to checking your programs.
    • Make a table of expected outputs (complete for Boolean; incomplete for normal functions)
    • We should more frequently put tests in our definitions pane as a development strategy.

Upcoming Work

• Homework.
  • Due Tuesday night at 10:30 p.m.
• Lab writeup for today: Exercise 3, http://bit.ly/151-2015S-lab16
• Reading for Tuesday:
  • Making and Manipulating Homogeneous Lists

Extra Credit Opportunities

Academic

• TEDx Grinnell, February 21
• Pioneer Diversity Council talk

Peer Support (Morning Section)

• Julia's radio show, "The Hot Box". Wednesday night/Thursday morning 1:00-2:00 a.m.
• Host a prospie!

Other Good Things

• Women's Basketball vs. Knox on Wednesday.

Questions

Do we have to document if it doesn't say so on the homework?

6P's required for anything that say "write and document". 6P's appreciated for everything else. At least a sentence for everything.

New Concepts from the Reading

• lambdas without definitions. If you have a function you don't need multiple times, there's no need to define it.
  • We don't write

    (define partial-sum (+ 2 3)) (* 8 partial-sum)

  • We instead write (* 8 (+ 2 3))
  • Similarly, we don't have to write (define only-blue (lambda (irgb-color) (irgb 0 0 (irgb-blue irgb-color)))) (image-variant kitten only-blue)
  • We can substitute the lambda in ourselves (image-variant kitten (lambda (irgb-color) (irgb 0 0 (irgb-blue irgb-color))))
• Compose (o and compose)
  • See whiteboard.
  • Lets you do more than one thing at a time.
  • A way to create new procedures
  • Can be faster for some things
  • Another way to sequence operations
  • Fewer parentheses!
  • Finally, something that's potentially comprehensible in Scheme

Lab