EBoard 11: Conditionals

Warning! You are being recorded (and transcribed) (provided the technology is working correctly).

Approximate overview

• Administrative stuff [20 min]
• Lab [60 min]

Administrative stuff

• Happy Valentine’s Day (or Ash Wednesday). I brought you a Valentine’s day present: Stickers.
• As an experiment, I’m going to answer questions on conditionals on Friday, rather than today.
• Friday is scheduled as a “pause for breath”, a time for all of us to catch up a bit (including finishing today’s lab).

Token activities

Academic/Scholarly

• Thursday, 2024-02-15, 11:00–noon, JRC 101. Scholars’ Convocation: Gaile Pohlhaus on “An Epistemology of the Oppressed: Resisting and Flourishing under Epistemic Oppression”.
• Thursday, 2024-02-15, 4:00pm, Science 3821. CS Extras: Peter Michael Osera on The Missing Link Between Programming and Proving.
• Thursday, 2024-02-15, 7:00pm, Science 3819. Mentor session.
  • Try to show up on time.
• Tuesday, 2024-02-20, noon–1:00pm, Some PDR. CS Table.

Cultural

• Thursday, 2024-02-15, 7:00–9:00pm, Sebring-Lewis. Jazz Concert w/Carol Welsman.
• Friday, 2024-02-16, 4:00–5:00pm, HSSC N1170 (Global Living Room). Middle of Everywhere.
• Sunday, 2024-02-18, 7:00–9:00pm, Harris Cinema. The Moth Storytelling Slam.

Peer

• Friday through Sunday, 2024-02-16 through 2024-02-18. Osgood Pool. Midwest Swimming and Diving Conference Championships.
  • 30 minutes counts.
  • Up to two separate sessions.
• Sunday, 2024-02-18, Simpson College Baseball Diamond. Baseball.
• Friday, Main Quad, Slumber Party!

Wellness

• Tuesday, 2024-02-20, noon-1pm, BRAC P103. HIIT and Strength Fitness Class.
• Tuesday, 2024-02-20, 12:15–12:50, Bucksbaum 131. Yoga in the Museum.
• Tuesday, 2024-02-20, 4pm, BRAC P103 (Multipurpose Dance Studio): Yoga.

Misc

Other good things (no tokens)

• Saturday, 2024-02-17, 1:00–3:00pm, Darby. Men’s Basketball vs. Monmouth.
• Saturday, 2024-02-17, 2:00–5:00pm, Field House. Women’s Tennis vs. Ottwawa.
• Saturday, 2024-02-17, 3:00–5:00pm, Darby. Women’s Basketball vs. Monmouth.

Upcoming work

• Wednesday, 2024-02-14, 11:00pm, SoLA 1 due
• Friday, 2024-02-16, 8:30am (or as early as 8:00am): Quizzes.
  • New: Conditionals
  • Old: Tracing
  • You may bring one page of hand-written notes.
• Thursday: No reading responses!
• Friday, 2024-02-16, 11:00pm: SoLA 1 post-reflection
  • Try to do it earlier.
• Friday, 2024-02-16, 11:00pm: MP3 pre-reflection
• Monday, 2024-02-19, 8:30am: Submit today’s lab writeup.
  • Submit on Gradescope
  • Preferred: Submit before the end of class Friday.
• Wednesday, 2024-02-21, 11:00pm: MP3

Notes on MP3

Sam decided to rewrite it completely. Ran out of time. But getting close.

• A bunch of RGB transformations.
• A bunch of HSV transformations.
• A few more of your own.

Questions

Administrative

Do we need to submit the sample LA.

No.

Sam thinks he’s funny, but he’s not.

Misc

Lab

Exercise 1a

Please use #t for true and #f for false.

(remainder dividend divisor) tells you what’s left over after you divide dividend by divisor.

Exercise 1b

What’s wrong with this?

(define is-even?
  (lambda (n)
    (if (zero? (remainder n 2))
        #t
        #f)))

(define is-even-integer?
  (lambda (n)
    (if (and (integer? n) 
             (zero? (remainder n 2)))
        #t
        #f)))

Is it correct? It seems to be.

How would we make it better?

Since we’ve already defined an is-even? predicate, we should be using it.

(define is-even-integer?
  (lambda (n)
    (if (and (integer? n) 
             (is-even? n))
        #t
        #f)))

If (and (integer? n) (is-even? n)) is #t, we return #t

If (and (integer? n) (is-even? n)) is #f, we return #f

We’re just returning the result of the test, so we can return the value of the test, rather than putting it in an if.

(define is-even-integer?
  (lambda (n)
    (and (integer? n) 
         (is-even? n))))

Just like we don’t normally write (* 1 (+ 0 exp)), if our test just returns #t or #f, we normally don’t write the if part.

Are the following employee ids?

• “12345/6”
• “12435.0”

Don’t worry if they are not.

For the quiz, I expect that you will have finished only exercise 1.