Held: Friday, 27 February 2015

Back to Outline 22 - Images as Functions from Position to Colors. On to Outline 24 - Recursion Basics.

Summary

We explore further details of Scheme's lists. Lists are an important mechanism for structuring data. We also consider how lists can be used to represent drawings.

Related Pages

• Reading: Building Data Structures with Heterogenous Lists
• Lab: Building Data Structures with Heterogeneous Lists
• Reference: Important List Procedures
• Morning EBoard 23 (Source a.m. 23)
• Afternoon EBoard 23 (Source p.m. 23)

Overview

• Lists, revisited.
• New list operations.
• Drawings as values.

Administrivia

• Continue partners.
• Review session Monday at 7:00 p.m.
• Office hours today at 10:00 a.m.
  • http://rebelsky.youcanbook.me
• One of your classmates passed along the following article which you might find interesting.
  • http://www.wired.com/2015/02/science-one-agrees-color-dress/
• Prospies Monday! Be prepared for special activities.
• Friday PSA
  • In making choices this weekend, please make sure that Nobody Gets Hurt (including you).
  • There are a lot of illnesses going around campus. Rest will help you avoid them better than almost anything. (I'm telling myself the same thing.)

Upcoming Work

• Homework 6.
  • Due Tuesday at 10:30 p.m.
• Exam 2 to be assigned on Tuesday.
• No lab writeup for today.
• Reading for Monday: Recursion Basics
  • Recursion Basics
  • A cool and different topic that we'll be talking about through spring break (and the rest of the semester).

Extra Credit Opportunities

Academic

• CS Table Friday - Art, CS, and Artificial Intelligence.

Peer Support (Morning Section)

• Julia's radio show, "The Hot Box". Wednesday night/Thursday morning 1:00-2:00 a.m.
• Host a prospie.
• Indoor Track this Saturday. Support Grinnell Pride!
• Neverland Players Friday and Saturday at 7:00, Sunday at 1:30 and 7:00
• Grinnell Singers Sunday at 2pm. Handel's Esther. Maybe Sebring Lewis.
• Orchestra a week from Saturday.

Peer Support (Afternoon Section)

• Indoor Track this Saturday. Support Grinnell Pride!

Other Good Things

• Neverland Players this weekend.

Lists

• Our first encounters with lists.
  • Collection of values
  • Homogeneous: All the values in a list are the same type
  • Used primarily with map
• Extending that notion
  • Can also be heterogeneous: Values in the list may have multiple types.
  • Can examine individual elements with car, cdr, and list-ref.
  • Can be extended (creating new lists) with cons.
  • There's an empty list: null.
• Why is the new view important?
  • It will soon give us the opportunity to manipulate lists in new and interesting ways.

Implementing Drawings

• We can (and do) use lists to implement drawings.
• The reading considers a simplified representation, in which the width and height of a drawing are the same.
• But the general process is the same
  • Group the values in a list
  • When we need to render or manipulate a drawing, use the list operations to extract parts.

Lab