Held: Friday, 12 September 2014

Back to Outline 08 - Documenting Programs and Procedures. On to Outline 10 - Testing Your Procedures.

Summary

We consider a few important procedures that get called for their effect on the system (or on a value), rather than for the value returned. These procedures have "side effects". We focus on two kinds of procedures with side effects: Procedures that display text on the screen, and procedures that work with images, including images stored in files.

Related Pages

• Reading: Output in Scheme
• Reading: Basic Image Operations
• Lab: Side Effects
• EBoard (Source) (HTML)

Overview

• Output with display and newline.
• Using output procedures to trace code.
• More procedures for working with images.

Administrivia

• Maintain lab partners from yesterday.
• Quick observations from epilogues
  • Part D was clearly the hardest part. I hope it was useful.
  • Epilogues should be individual. Don't do them with your partner.
  • A bit of frustration on lack of textbook and availability of help.
  • I generally expect homework assignments to take 2-4 hours.
  • Mostly positive group experiences, but some scheduling difficulties.
  • Sunday mentor hours?
• Favorite quote: "It seems like every time I think something is going to be easy, it's complex, and every time I think something is going to be complex, it's easy."
• It's weekend. Please reflect in advance on what decisions will be appropriate for you. And if you choose to drink, please drink responsibly.

Upcoming Work

• Lab writeup (due Monday): Exercise 3a (annotated versions of each of the drawing procedures). http://bit.ly/151-2014F-w09
• Reading for Monday:
  • Testing Your Procedures

Campus Events of Interest

• Rosenfield seminar on Scotland, Monday (noon?)
• Rebecca Hamlin book talk Wednesday at 4:15 pm.

Extra Credit Opportunities

Academic

Peer Support

• Football Games (???)
• Women's Volleyball (Sat 9/13 @ 2pm and 4pm and Sun 9/14 @ 11am and 1pm in Darby.)
• Men's Tennis (???)
• Women's Tennis (???)
• Anna Christie, Oct. 9-12 (SB plays Marthy)

Output

• Use display to print values.
• Use newline to print a newline.

Tracing Code with Output

• By inserting appropriate calls to display and newline, we can better see what our program does.

More Image Procedures

• image-new - create a new image
• image-show - you know
• drawing->image - you know
• image-load - load an image from a file
• image-save - save an image to a file
• drawing-render! - put a drawing on an image