Held: Tuesday, 3 February 2015

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
• Morning EBoard 9 (Source a.m. 9)
• Afternoon EBoard 9 (Source p.m. 9)

Overview

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

Administrivia

• New partners!
• We've seen more DrRacket crashes this semester than in the past few years combined. And we're not sure why.
  • Save regularly!
  • Save a backup!

Upcoming Work

• Assignment 3.
  • Due TONIGHT at 10:30 p.m.
  • Don't forget the prologue and epilogue!
• Exam 1 to be distributed tomorrow
• Lab writeup for lab 9 (today), http://bit.ly/151-2015S-lab09
• Readings for Wednesday:
  • Testing Your Procedures

Extra Credit Opportunities

Academic

• Wednesday, February 4, 12:00 noon, JRC 101, Scholars' Convication: "The Fight for Economic Justice from the Streets of Chicago" by Virginia Parks.
• Any other event in this Rosenfield symposium.
• Thursday extra this week.
• Friday, February 6, 12:00 noon, Science 3821, CS Table, Summer Research Opportunities for CS Students
• TEDx Grinnell, sometime in February.

Peer Support (Morning Section)

• Julia's radio show, "The Hot Box". Wednesday night/Thursday morning 1:00-2:00 a.m. Next week's theme might be Summertime
• Swimming, Conference Championships, February 13-15, The Osgood
• Track and Field, Saturday at 10 a.m., the Bear Fieldhouse

Peer Support (Afternoon Section)

• Swimming, Conference Championships, February 13-15, The Osgood
• Track and Field, Saturday at 10 a.m., the Bear Fieldhouse
• Men's Basketball, Saturday at 3:00 p.m., New Darby

Recommended Events (no EC unless mentioned above)

• #OneGrinnell, Wednesday, February 4 at 4:15 p.m.

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