EBoard 07: Cut and compose (Section 2)
Today’s start-of-class procedure
- Plan to sit with your partner from last class (in the same place).
- Greet each other.
- Log in.
- Bring up the lab.
Warning! You are being recorded and transcribed, provided the technology
is working correctly.
Approximate optimistic overview
- Administrative stuff [10 min]
- Some academic integrity issues [5 min]
- About Wednesday’s quiz [5 min]
- About reducing redundancy [5 min]
- About MP3 [15 min]
- Questions [5 min]
- Lab [30 min]
- Turn in lab [5 min]
Administrative stuff
Introductory notes
- I’m running out of time on Otter.ai, so I’ll only be recording section 1.
- Please try to avoid putting images and colors in the definitions pane.
When you do so, your Racket file ends up saving in a strange format that
doesn’t work with Gradescope. Yay computers!
- I’d also recommend that you do without
image-load and image-save in
the definitions pane.
Upcoming activities
Scholarly
- Thursday, 13 February 2025, 11:00 a.m.–Noon, JRC 101.
Grinnell Lecture: Darrius Hills on “The Achievement of Identity: Soul Work, Salvation, and Black Manhood in the Religious Imagination of James Baldwin”.
- Tuesday, 18 February 2025, Noon–12:50 p.m., PDR 224C (White Dining Room).
CS Table: ???
Artistic
- Friday, 7 February 2025, 3:00–5:00 p.m., Burling Digital Studio.
Make a Fidget Workshop.
- Tuesday, 11 February 2025, 4:00–5:00 p.m., Bucksbaum 131 (GCMoA).
Gallery Talk with Chen, Kluber, and Tavares.
- Friday, 14 February 2025, 5:00–6:30 p.m. (talk at 6:00), 926 Broad St (Stewart Arts Building).
Opening Reception for Artist Salon: Works by Grinnell College Art Majors
Multicultural
- Friday, 7 February 2025, 4:00-5:00 p.m., HSSC N1170 (Global Living Room)
Middle of Everywhere: How to Order a Coffee in Singapore.
Peer
Musical, theatric, sporting, and academic events involving this section’s
students are welcome.
Wellness
- Friday, 7 February 2025, 5:30–8:00 p.m., Downtown Grinnell.
The Sweet Stroll.
- Tuesday, 11 February 2025, 12:15–12:50 p.m., GCMoA.
Yoga in the Museum.
- Tuesday, 11 February 2025, 4:30–6:30 p.m.,
BRAC P103 (Multipurpose Dance Studio).
Wellness Yoga.
Misc
- No particular date. Cyberspace.
Fill out the survey at https://www.surveymonkey.com/r/GrinnellParksandRec.
- Sunday, 9 February 2025, 7:30–8:30 p.m., Science 3819.
Mentor Session.
- Tuesday, 11 February 2025, 7:00–8:00 p.m., Science 3820.
Mentor Session.
- Tuesday, 18 February 2025. 6:00–7:00 p.m., HSSC A1231.
Make a Portfolio Website.
Other good things
These do not earn tokens, but are worth your consideration.
- Saturday, 2025-02-08, 1:00–3:00 p.m., Natatorium.
Swimming Last Chance Meet
- Saturday, 2025-02-08, 1:00–3:00 p.m., Darby.
Women’s Basketball vs. Lake Forest
- Saturday, 2025-02-08, 3:00–5:00 p.m., Darby.
Men’s Basketball vs. Lake Forest
Upcoming work
- Friday, 2025-02-07 (today)
- Sunday, 2025-02-09
- Tuesday, 2025-02-10
Friday PSA
- You are awesome.
- People care about you.
- Please take care of yourself.
- Please be moderate.
- Choose what is right for you.
- Consent is essential, but insufficient.
Academic Integrity
Example one: A student comment from mini-project 2.
For the pentagon, I did get a little bit of help from the programming
assitant chatgpt, I was having trouble with knowing how to incorporate
real-part, imag-part, and tying it all together.
- Thanks for citing.
- However, Do not use AI programming assistants!
- Ask a human being. Don’t ask the computer.
- There are (at least) two kinds of evening help
- Evening tutors (Sunday through Thursday, 7-10 p.m.): Answer
questions individually. (Also Sunday 3-5)
- Mentor sessions (Sunday 7:30-8:30, Tuesday 7-8): Review sessions.
Example two: Some code from mini-project 2
(build-list sides (lambda (i) (make-point side-length (general-radius sides) (general-theta sides) (+ 2 i))))))
- Hmmmm … I haven’t taught you
build-list. So the student found it on the
Interweb. (Hopefully not with ChatGPT.)
- Let’s see where (of course, they cited it).
- Nope.
- Please cite!
- In general, I’d prefer that you not go far beyond what we’ve learned in class.
Example three: Strange file uploaded
- Be careful to upload the right file.
About Wednesday’s Quizzes
There are many goals and processes for decomposition. Not only are we
breaking a big problem into smaller parts, we are also trying to avoid
repeating ourselves.
In many cases, I saw that you did some decomposition well, but left some
repeated code. My initial inclination was to mark all of those as “Redo”.
After some reflection, I decided that talking about it in class would suffice.
If there’s more than one case of repetition, you have a redo. If there’s
only one, you have an S.
On to the problem itself …
About reducing redundancy
Sam, how do I reduce redundancy in my compute-pentagon-point procedure?
(define compute-pentagon-point
(lambda (radius num)
(pt (real-part (make-polar radius (* 2/5 num pi)))
(imag-part (make-polar radius (* 2/5 num pi))))))
- First of all, great job on using the radius, rather than the side length,
so that you don’t have to duplicate the conversion of side length to
radius!
- Second, TPS!
(define that-point
(lambda (radius num)
(make-polar radius (* 2/5 num pi))))
(define compute-pentagon-point
(lambda (radius num)
(pt (real-part (that-point radius num))
(imag-part (that-point radius num)))))
Another solution
(define polar->point
(lambda (polar)
(pt (real-part polar)
(imag-part polar))))
(define compute-pentagon-point
(lambda (radius num)
(polar->point (make-polar radius (* 2/5 num pi)))))
A solution that I’d prefer you not use (yet).
(define compute-pentagon-point
(lambda (radius num)
(define polar (make-polar radius (* 2/5 num pi)))
(pt (real-part polar)
(imag-part polar))))
Sam doesn’t like this last version because
- It uses
define within define, which is known to cause weird behavior.
- It avoids decomposing the procedure into subprocedures. More this.
Lessons:
- When confronted with repeated code, you may be tempted to put the repeated
code in a separate procedure (good temptation), but you should also put
the enclosing code in a separate procedure (also a good temptation).
- Think about the kinds of values you’re working with and how you change
them to other kinds of values.
- Break complicated things into smaller parts. (Aka, decompose)
About Mini-Project Three
Q&A
Administrative
Do I have to tell you when I’m spending a token to turn something in late?
No.
I got an I on MP1. Will you charge me tokens for redoing MP1?
No.
I got an I on MP2. Will you charge me tokens for redoing MP2?
Yes. Tokens are my way of encouraging you to make sure you make an
appropriate start on mini-projects.
When do we make up quizzes?
Option 1: During the next quiz day, there will (usually) be make-ups
for past quizzes. (They aren’t identical.)
Option 2: On the SoLA (take-home exams).
Can you tell us more about take-home exams?
Yes, when I distribute them. But not today.
Is it okay that I learned things from the Racket Web site and cited them?
Yes.
When redoing a mini-project do I have to start over?
Generally, no. Just fix the parts that we tell you need fixing.
What should documentation look like?
;;; (PROCEDURE PARAMS) -> type?
;;; PARAM : type?
;;; PARAM : type?
;;; PARAM : type?
;;; SHORT DESCRIPTION OF WHAT THE PROCEDURE DOES.
;;; (compute-pentagon-point side num) -> point?
;;; side : positive-real?
;;; num : integer? (in the range 1 .. 4)
;;; Compute one point on a pentagon, numbering them clockwise.
If I used one semicolon rather than three, do I need to resubmit.
Nah.
Cool?
Of course. It’s winter in Iowa.
Readings
MP3
Lab
Same partners, new submission