EBoard 11: Conditionals, Part 2 (Section 1)

Please sit with your partner from Monday’s class.

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

Approximate overview

• Administrative stuff
• Lab

Administrative stuff

Introductory Notes

• Warning!
• Grade reports were distributed last night.
  • Let’s take a look at one.
• As I mentioned in the course syllabus and email, I will be turning in academic alerts for anyone who has fewer than two LAs completed or a missing MP1. I may also turn one in for those of you who are missing many reading responses.
  • AAs are intended to ensure that you get appropriate support.
  • If you have fewer than two LAs completed, you should probably set up an appointment with me to get help and/or look at ways to move forward successfully. https://bit.ly/book-samr or drop me an email/TM to find another time.
  • If you have fewer than two LAs completed, you should also be making sure to use mentor sessions and/or asking evening tutors for help.
• Additional times available for meetings this week.
  • Wednesday: 1:15–2:30 p.m.
  • Thursday: 8:00–9:30 a.m. and 4:30–5:00 p.m.

Notes on Mini-Project 1

• Mini-project 1 is now available on Gradescope.
• I’ll demo how you might look at your graded work.
• There were a lot of “close, but still missing a few things” submissions. Hopefully, those will be easy to fix.
• You can submit redos on Gradescope
• Some students turned in nearly-identical solutions.
  • You should feel free to consult each other, but YOU MUST CITE.
  • I’ll treat this first instance as a failure to understand that policy.
  • In the future, I’ll need to report apparent collaboration that lacks citation.

Strange answers

From the latest reading responses:

(define (shorter? str1 str2)
  (< (string-length str1) (string-length str2)))

While this is valid Scheme, it is not valid Scamper. That makes me question how someone would come up with this answer. (The obvious reason is “AI”.)

• You may not use AI in this class.
• If you ask others for help, YOU MUST CITE them.
• It’s okay to get problems wrong on reading responses please rely primarily on your understanding.
• Please try your answers in Scamper (unless the problem suggests otherwise).

Upcoming activities

Scholarly

• Thursday, 24 September 2026, 11:00 a.m.–noon, Herrick Chapel. Scholars’ Convocation: The Story of Our Founding: America at 250 with Annette Gordon-Reed
• Tuesday, 29 September 2026, Noon–1:00 p.m., JRC 224C (I think). CS Table New
  • Topic TBD

Artistic/Cultural

• Any day. Visit the GCMOA for at least 30 minutes.
• Thursday, 24 September 2026, 7:00–9:00 p.m., The Wall. Broadway Musical Karaoke New
  • I’m not certain about this one; check the signs.
• Friday, 25 September 2026, 7:30–9:00 p.m., Sebring-Lewis. Jazz Ensemble: Terry Riley’s “In C”
• Saturday, 25 September 2026, 2:00–3:30 p.m., Sebring-Lewis. Grinnell Symphony Orchestra Concert New
• Saturday, 26 September 2026, 7:30–9:00 p.m., Sebring-Lewis. Grinnell Singers: My Heart Be Brave New

About “In C”

When Terry Riley brought 10 musicians into a New York City studio in 1968 to record an album-length version of his composition “In C”, he couldn’t have known how profoundly he was about to affect the course of contemporary music, both popular and experimental. Minimalist music was around before In C, but this was the album that really put that approach on the map. Influenced by everything from Indian music to John Cage’s chance-oriented pieces, this modal marvel is a cyclical composition consisting of short, repetitive phrases that each player chooses spontaneously from the score, creating a hypnotic interlocking of lines based around a central idea. Piano, vibes, marimba, woodwinds, horns, and viola meld together in a slowly shifting, pointillist landscape. When the album was released, composers like Steve Reich and Philip Glass were following minimalist paths as well, but they were still pretty far underground. In C not only broke through to avant-garde ears, it proved profoundly influential to adventurous rock and jazz artists.

Multicultural

• Friday, 25 September 2026, 4:10–5:00 p.m., HSSC N1170. Middle of Everywhere (Singapore)

Peer

Musical, theatric, sporting, academic, and similar events involving this section’s students are welcome.

• Saturday, 26 September 2026, 11:00 a.m.–1:00 p.m., Springer Field. Soccer vs. Ripon
• Saturday, 26 September 2026, 1:00–4:00 p.m., Rosenbloom Field. Football vs. Beloit

Wellness

• Wednesday, 23 September 2026, 6:30–8:00 p.m., Bear Dance Studio. Brazilian Jiu-Jitsu
• Friday, 25 September 2026, 6:30–8:00 p.m., Bear Dance Studio. Brazilian Jiu-Jitsu
• Monday, 28 September 2026, 6:30–8:00 p.m., Bear Dance Studio. Brazilian Jiu-Jitsu
• Monday, 28 September 2026, 8:00–9:00 p.m., Prayer Garage. Meditation Group
• Tuesday, 29 September 2026, 4:30–6:00 p.m., Bear P103. Wellness Yoga
• Wednesday, 30 September 2026, 4:15–5:45 p.m., Undisclosed Location. Forest Bathing
• Saturday, 10 October 2026, All Day, Somewhere. Mental Health Training.
  • Sign up on Handshake.
  • It’s all day, so you will earn 3 tokens.

Misc

• Wednesday, 23 September 2026, 8:00–9:00 p.m., Science 3820. Mentor Session
• Thursday, 24 September 2026, 8:00–9:00 p.m., Science 3820. Mentor Session
• Friday, 25 September 2026, 5:00 p.m.–???, Merrill Park West CS Picnic

Other good things

These do not earn tokens, but are worth your consideration.

Upcoming work

• Due Thursday, 2026-09-24
  • Today’s Lab
    • Submit lab on Gradescope
    • Please submit at the end of today’s class.
  • Readings (forthcoming)
• On Friday, 2026-09-25:
  • New Quiz/LA on conditionals.
  • MAKEUP Quiz/LA on compose, cut, and section.
  • MAKEUP Quiz/LA on tracing.
  • MAKEUP Quiz/LA on decomposition.
  • MAKEUP Quiz/LA on procedures.
• Due Tuesday, 2026-09-29
  • Mini-project 2
    • Submit on gradescope
• Due Tuesday, 2026-10-06
  • Mini-project 1 redo

Questions

It’s a “bribe for asking questions” day.

Administrative questions

What happens if I fail to indent my code on a mini-project?

You will get a not-yet-satisfactory grade.

Can I submit a lab writeup or reading response that is missing?

You may not submit lab writeups or reading responses more than 48 hours after they are due. The “the first six don’t count” rule is intended to accommodate missing ones.

How many chances to I get to make up MP1?

First redo is free.

Second redo costs a token.

I hope we won’t need a third redo.

How do I sign up for the CS picnic?

Deadline was Monday. We provide the food. (There’s probably enough if a few of you show up without having RSVP’d.)

Questions on MP2

I tried running the code in part 1c of the mini project following the rounding procedure given in the instructions but kept getting an error that said “expected rgb component, received number”. How do I fix this?

It’s a problem with how the rgb function works in some versions of Scamper. You may have to use (min 255 (* 32 (round (/ 255 32))))>

Post additional questions on Teams.

Questions on conditionals

Can we nest cond expressions within if, or, and and? (And can we nest those within each other?)

Yes. However, it can become hard to read if you do too much nesting.

Can we still use cut operation and composition with conditionals?

You cannot use composition or the section operations (l-s and r-s) with conditionals, since the conditional operations aren’t functions. However, you can use the cut operation (with # and %) with conditionals. I’d prefer that you didn’t.

Why does (and) with no parameters give #t, and (or) with no parameters give #f?

Answer 1 :and returns #f if any of its arguments are #f. In (and), none of the arguments are #f. Similarly, or returns #t if all of its parameters are #t. None of its parameters are #t.

Answer 2: Computer scientists are weird.

Answer 3: It’s easier to implement them that way.

Lab

If you finish early, please do the extra problems.

If you finish those, too, split up and start working on MP2.