Overview

• Preliminaries
  • Admin.
  • About HW 3.
  • Clicker Questions.
• The need for documentation.
• The Six P's - a strategy for documenting procedures.
• A few additional P's.
• Practice.

Admin

• First lab writeup due Friday. It's supposed to be quick and easy (assuming you've done the problem).
• "Sam, what color names are available?"
  • (ggimp-rgb-list)
  • Or create your own with (irgb-new RED GREEN BLUE))
• Warning! Friday the 13th falls on a Friday this month.
• I've put the "calling order" on the board today.
• Reminder: Mentor sessions are Thursdays and Sundays at 7:30 pm.
• Reminder: Quiz Friday on Drawings as Values, Procedures, and maybe a bit about documentation.
• Reading for Friday
  • The GNU Image Manipulation Program
• EC Opportunities:
  • Humanities Center Speaker Sarah Hendron TONIGHT Sept. 11, 7:30 p.m., JRC101 Waking the Machines: Art, Design, and Adaptive Technology
  • CS Table Friday (Reflections on Trusting Trust; NYT on NSA)
  • Men's Soccer, 1:30pm, Here. Nebraska Wesleyan (sp?)
• Other things
  • Feminist Action Coalition is having a "rethink ourselves" meeting tonight at 8:00 pm. (Younker)

HW 3

• We went over the homework (available online)
  • You know everything you need to know to do this assignment
  • No, you don't need to know how to make spirals to do this assignment
  • You can get a smile by overlaying two circles

Clicker Questions

• Today's clicker questions are about procedures (retrospective) and documentation (coming later)

The need for documentation

• Code isn't always obvious. Does it accomplish what it's supposed to? How do we know?
  • We write notes in English that explains

Recolor the image red, ignore that recolored image, and then enlarge it

Recolor the image and make it larger

• Human-language text that describes computer code is called "Documentation"
• Written for multiple audiences: "Know your audience"
  • You - What do I want the code to do?
  • Someone who has to fix your code - What do you want the code to achieve and how do you achieve that goal?
  • Someone who has to USE your code
• We usually embed these in the code as comments
• In Scheme, comments begin with a semicolon$a
• Our focus will be comments for clients

• "Six P's"

  • Procedure - name
  • Parameters - inputs to the program, give their name and type
  • Purpose - A quick explanation in English
  • Produces - name and type the result
  • Preconditions - Limits on input (usually)

  • Postconditions - An attempt to formally specify what

    ;;; Procedure: ;;; square ;;; Parameter: ;;; n, a real number ;;; Purpose: ;;; square n ;;; Produces: ;;; result, a number of the same type as n ;;; Preconditions: ;;; [No additional] ;;; n != 0 ;;; Postconditions: ;;; nn = result ;;; (equals? ( n n) result) ;;; result is positive e (define square (lambda (num) drawing-unit-square))

  Note: If we're using inexact numbers, this may not always be true

The Six P's - a strategy for documenting procedures

A few additional P's

Practice