EBoard 11: Conditionals (Section 2)

Approximate overview

• Administrative stuff [30 min]
• Questions [5 min]
• Lab [45 min]

Administrative stuff

• I’m Sam. I’m replacing Prof. Perlmutter for today.
• Happy Valentine’s Day (or Ash Wednesday). I brought you a Valentine’s day present: Stickers.
• Friday is scheduled as a “pause for breath”, a time for all of us to catch up a bit (including finishing today’s lab).

Upcoming work

• Wednesday, 2024-02-14, 11:00pm, SoLA 1 due
• Friday, 2024-02-16, 3:35pm: 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, 2:30pm: Submit today’s lab writeup.
  • Preferred: Submit before the end of class Friday.
  • Please try to finish on your own if we don’t finish in class.
• 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-based transformations.
• A bunch of HSV-based transformations.
• A few more of your own.

What Sam typed in DrRacket

Sorry. The HSV colors didn’t paste. But you can re-run the code to see what happens.

> (hsv 0 100 100)
.
> (hsv 120 100 100)
.
> (hsv 240 100 100)
.
> (hsv 60 100 100)
.
> (hsv 300 100 100)
.
> (hsv 270 100 100)
.
> (hsv 330 100 100)
.
> (hsv 0 100 100)
.
> (hsv 0 50 100)
.
> (rgb->string (hsv->rgb (hsv 0 50 100)))
"255/128/128"
> (hsv 0 0 100)
.
> (rgb->string (hsv->rgb (hsv 0 0 100)))
"255/255/255"
> (hsv 0 100 100)
.
> (hsv 0 100 50)
.
> (hsv 0 100 70)
.
> (rgb->string (hsv->rgb (hsv 0 100 70)))
"178/0/0"

Questions

Administrative

Misc

Lab

Exercise 1a

Please use #t for true and #f for false (no quotation marks).

(remainder dividend divisor) tells you what’s left over after you divide dividend by divisor. So (remainder n 2) tells you how much is left over after dividing by 2 (either 0 or 1).

Exercise 1b

What’s wrong with the following for is-even-integer?

Excercise 1c

What do you expect for each of the following?

> (number-not-integer? 3)
#f
> (number-not-integer? 3.5)
#t
> (number-not-integer? 3/4)
#t
> (number-not-integer? "three")
#f

Exercise 1d

(<= x y z) is a shorthand for (and (<= x y) (<= y z)).

• If the test holds, y is the median.

Make sure to think about the following

> (median-of-three 1 2 3)

> (median-of-three 3 2 1)

> (median-of-three 3 3 2)

> (median-of-three 2 2 3)