• Continue partners.

Overview

• Preliminaries.
  • Admin.
  • Upcoming Work.
  • Extra Credit.
  • Questions.
  • Quiz.
• Group Testing Exercise.
• Lab.

Preliminaries

Admin

• SR not CC
• Beware! It's Friday the 13th (day of class)
• Friday PSA.

Upcoming Work

• Reading for Monday Boolean Values and Predicate Procedures
• [Exam 1]
  • Electronic version next Tuesday
  • Printed version next Wednesday
• No writeup!

Extra Credit Opportunities

Academic

• John Gerrard talk, "Corn Bomb", Monday at 8pm
• No CS Table next week - It's advising week!
• Wednesday CS Extra Next week, 4:15 in 3821: Ursula Wolz on Building Coding Communities
• Thursday CS Extra Next Week, 4:15 in 3821: SamR on The Architecture of Mediascript

Peer Support

• Lots of parents weekend events
• 4pm Dance at Bear Multipurpose Dance Room for Latin Heritage Month

Questions

Can I use <> multiple times in section?

Yes. Each is treated as a separate input.

You probably won't want to do this with one call to section on problem 1.

Composition is your friend.

I feel like I saw something really like problem 2 somewhere. Can you tell me where?

Homework assignment 3.

Do we have homework in addition to the exam?

No!

How should we provide examples?

Write in interactions pane. Copy, paste, comment out with semicolons.

What should we do if something says "the highest component of a color" and two components are equally large, such as (irgb 200 0 200).

Option 1: It's up to you which of the largest components you use.

Option 2: Good specifications - Failed to meet preconditions - Whatever you want.

What should we do if people don't meet the preconditions?

If you say that the preconditions are "verified", you must issue an error message.

If you say that the preconditions are "unverified" (or you don't say anything about their being verified), the assumption is that youre procedure can do anything if they are not met.

Should that question help me think about problem 2?

Probably.

Key ideas in testing

• Useful to think about what procedure is supposed to do; helps clarify our approaches.
• Not easy to write good tests.
• Test some "obvious things"
• Think about "edge cases" or "corner cases" - The things at boundaries where stuff might go wrong
• Requires practice

Testing Exercise

What tests would you write for the following procedure?

;;; Procedure:
;;;   classify-triangle
;;; Parameters:
;;;   side1, a rational number [unverified]
;;;   side2, a rational number [unverified]
;;;   side3, a rational number [unverified]
;;; Purpose:
;;;   Determine the kind of triangle the three sides describe.
;;; Produces:
;;;   classification, a string 
;;; Preconditions:
;;;   side1, side2, and side3 together describe a triangle [verified]
;;; Postconditions:
;;;   If all three sides are equal, classification is "equilateral".
;;;   If exactly two sides are equal, classification is "isosceles".
;;;   If no two sides are equal, classification is "scalene".

• At least one of the sides is negative should result in an error (check-error (classify-triangle -2 -2 -3))
• Numbers really close to each other (check-equal (classify-triangle 2.00001 2.00002 2.00003) "scalene")
• Exact and inexact (check-equal (classify-triangle 8 8 8.0) "equilateral")
• Some non-triangles (check-error (classify-triangle 2 2 5)) (check-error (classify-triangle 0 0 0)) (check-error (classify-triangle 2 2 4)) ; A degenerate triangle (check-error (classify-triangle 2 5 2)) (check-error (classify-triangle 5 2 2))
• Things that aren't rational (check-error (classify-triangle 2+3i 3+4i 3+2i))
• General questions that we're not quite sure the answer about (check-equal (classify-triangle (sqrt 2) (sqrt 2) 2) "isosceles")
• Something obvious (check-equal (classify-triangle 7 7 7) "equilateral") (check-equal (classify-triangle 3 3 3) "equilateral")

Finish Lab