Held: Tuesday, 8 October 2013

Back to Outline 22 - Conditionals. 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: Heterogeneous Lists
• Lab: Heterogeneous Lists
• EBoard (Raw) (HTML) (PDF)

Overview

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

Administrivia

• Choose your own partners for today and the rest of this week.
• Upcoming EC opportunities
  • Tuesday, 7 pm, Road to Rio at pool
  • Thursday extra at 4:15: Grad school in CS
  • Friday CS Table: Reports from Hopper
  • Friday film: Codebreaker, 7pm, Harris
  • Post-Codebreaker discussion
  • Wit, the play, opens Thursday.
  • Any Queeer Culture Week Activity
    • E.g., Wednesday at 7:30, Consent, Negotiation, and BDSM,
  • ...
• Other upcoming stuff
  • Review session 1:15 pm Thursday
  • Mentor session 7:30 pm Thursday
  • Mentor session 7:00 pm Sunday
  • ...

Lists

• Original notion of lists:
  • Collection of values
  • Homogeneous: All the values in a list are the same type
  • Used primarily with map and for-each
• 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.
• 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