Class 17: Boolean Values and Predicate Procedures

Held: Monday, 20 February 2017

We consider a new type

Preliminaries

Overview

• Boolean values
• True vs. truish
• Predicates - procedures that return Boolean values
• Combining Boolean values with and and or

Related Pages

• Eboard 17 (Source)

• Reading: Boolean Values and Predicate Procedures

• Lab: Boolean Values and Predicate Procedures

Updates

News / Etc.

• New partners!
• I plan to return exam 1 this evening. I will also distribute some notes on the exam and an updated set of grades.
• I will hold class on March 1. I will not penalize you from missing provided you send me a short summary of what you did during class time.
  • “Sam, I spent class time contemplating the best approach to making our nation strong again.”
  • “Sam, I spent class time listening to a speaker suggesting ways to make our nation inclusive.”

Rotating reminders

• Use our tutors! We have tutors available Sunday through Thursday evening from 7-10 p.m. in Science 3813/15.

Upcoming Work

• Assignment 4 due TOMORROW at 10:30 p.m.
• Lab writeup, problem 2, due Wendesday before class.
• Reading: Conditionals

Extra credit (Academic/Artistic)

• CS Table, Tuesday at noon, 21 Feb 2017. Net neutrality. Reading packets should be available outside Curtsinger’s office or Orsera’s office.
• NEW Women in CS, Tuesday, 21 February 2017: Applying for GHC Scholarships and more! (All are welcome to attend.)
• Thursday extras, Thursday, 23 Feb 2017, 4:15 p.m., Science 3821: The Future of MathLAN
• Met Opera Live in HD showing of Rusalka, Saturday, Feb. 25. Talk 11:30-noon, opera noon-3pmish.
• Prazak Quartet, Tuesday, 28 February 2017, 7:30 p.m., Herrick.

Extra credit (Peer)

Good things to do

• Grinnell Equestrian Club Drill Team bake sale, 20 February 2017, 11am-2pm and 4pm-9pm.

The joy of trig.

• Remember SOHCAHTOA!
• For a circle, you can find the x and y coordinates of any point around the edge of the circle by …
• For an ellipse, we use a very similar formula.
• Details in eboard

Preparation

• What did you learn from the reading? (Let’s try to summarize for each other.)
• What questions do you have?

or and and as control structures

• How does normal procedure application work?
  • Evaluate all the parameters
  • “Plug them in to the body”
  • Evaluate the body
• How does or work?
  • It evaluates each parameter, in turn, until one holds (or it runs out of parameters).
  • As soon as one holds, it stops and returns that value.
• How does and work?
  • It evaluates each parameter, in turn, until one fails to hold (or it runs out of parameters).
  • As soon as one fails to hold, it stops and returns #f.
• This evaluation strategy means that we can use and and or to evaluate a sequence of expressions, stopping when we get the first acceptable one.

Lab

• Work on the lab
• Be prepared to discuss!