Held: Wednesday, 24 September 2014

Back to Outline 15 - Transforming Images. On to Outline 17 - Boolean Values and Predicate Procedures.

Summary

Today we explore Scheme's list data structure and some ways to use lists to make interesting images.

Related Pages

• Reading: Making and Manipulating Homogeneous Lists
• Lab: Making and Manipulating Lists of Drawings
• EBoard (Source) (HTML)

Overview

• Context: What and why lists?
• Building lists.
• Mapping lists.
• Other list operations.

Administrivia

• Continue lab partners.
• Prof. Weinman is running class today.
  
  • Extra credit for sending me notes to post on the eboard.
• Mentor sessions tonight at 8:00 p.m. and tomorrow night at 8:00 p.m.
• Office hours: Thu/Fri 1:45-3:15; Also walking hours Thu/Fri 1:15-1:45.
• Don't forget the review session Thursday at 10 a.m.!

Quiz Topics

• Integer-encoded RGB colors and the basic operations on those colors.
• Standard color transformations.
• Image and pixel operations, including image-variant and image-transform!.
• compose and o.
• (Possibly): lambda expressions, as used with the image transformations.
• (Not): map and the other subjects we are doing today.

Upcoming Work

• Lab writeup: Exercise 5 http://bit.ly/151-2014F-w16 Due Friday.
• Printed copies of lab due at the start of class.
• Homework 4 due next Tuesday.
  • Groups distributed via email.
• Reading for Friday:
  • Boolean Values and Predicate Procedures

Extra Credit Opportunities

Academic

• Convocation TODAY: Tara Zahra on Emigration from Eastern Europe
  • Please tweet interesting points with tag #GCConvo
• CS Extras Thursday at 4:30: Mathematical Image Synthesis Toolkit (MIST)
• CS Table Friday at noon: ???
• Campus Town Hall September 30

Peer Support

• Noteworthy, Sat., Sept. 27, 3:30 p.m. Herrick
• Science poster session, Sat., Sept. 27, morningish, science elbow
• Football Games (Saturday, Sept. 27, at 1pm)
• Men's Tennis (???)
• Women's Tennis (???)
• Swimming (???)
• Anna Christie, Oct. 9-12 (SB plays Marthy)
• Evan's radio show 5pm Friday nights on KDIC
• Donna's radio show Sunday midnight on KDIC

Miscellaneous

• Participate in #GrinWell. http://www.grinnell.edu/forms/sign-grinwell-presidents-wellness-challenge
• Friends of Drake Library needs help setting up for their annual booksale on Thursday, October 2 (conveniently, the same night as Grinnell High School's homecoming parade). You can help a good cause and probably get a few free books, too.
  • Update: They can also use help on Wednesday, October 1.

Context: What Are Lists?

• Issue: We'd like to make images with lots and lots of similar shapes.
• Problem: How to do so systematically.
• Solution: Scheme's list data structure and some related procedures.
• We're learning a new type, so it's useful to figure out some basic issues.

Building Lists

• (list val1 val2 ... valn)
• (make-list n value)
• (iota n)

Mapping Lists

• Basic operation: (map func lst). Apply a function to each element of a list.
• For images, we'll find it easier to do something like
  (map drawing-transform list-of-drawings list-of-values)

Other List Operations

• (append *lst1* *lst2*) - join two lists
• (reverse *lst*) - just what it sounds like
• (list-take *lst* *n*) - take the first n elements of a list
• (list-drop *lst* *n*) - drop the first n elements of a list

Lab

• Do the lab.
• Be prepared to reflect.