Overview

• Preliminaries.
  • Admin.
  • Upcoming Work.
  • Extra Credit.
  • Questions.
• More about procedures.
• Lab, continued.
• Questions and reflection.

Preliminaries

Admin

• Old partners!
• Today's lab is a continuation from Friday's class.
• Our graders sent back preliminary grades on your lab writeups. Those will generally be on a 0/1 scale (not submitted or significantly incorrect gets a 0; everything else gets a 1).
• If you would like to be added to the CS Department's Mailing List for events, please send me email.
• Quiz 2 returned. We need to talk about the last problem.
• Prospie!

Reminders

• Office hours: MTWF 10-11, Tu 1-2.
  • Sign up at http://rebelsky.youcanbook.me.
  • Also feel free to stop by when my door is open.
  • Or to email me for an appointment.
• Tutor hours
  • Sunday, 3-5 p.m.
  • Sunday-Thursday, 7-10 p.m.
• Weekly review sessions:
  • Wednesday at 8pm in the CS Commons with ?
  • Thursday at 10am in this room with SamR
  • Thursday at 8pm in the CS Commons with ?

Upcoming Work:

• Readings for Tuesday:
  • Simple Output in Scheme
  • Simple Input in Scheme
• Assignment 3 due tomorrow at 10:30 p.m.
• Lab Writeup: Exercises 3 ab and 5
  • Send email titled CSC 151 Lab Writeup 9 (Your Names)
  • Do not include the underscores.
  • Send to CSC151-02-grader@grinnell.edu
  • Due before class on Wednesday.

Extra Credit

• Send to rebelsky@grinnell.edu with subject "CSC 151 Extra Credit".

Academic

• This week's Rosenfield Symposium on Campaign Finance
• Monday, February 8, 4:15 p.m. in Bucksbaum 152, Miriam Langer enjoins you to "Do Your Work in Public" (part of the series "Digital in Public: Intellectual and Technical Skills for Making a Difference")
• Monday, February 8, 7:30-9:00, JRC 101: The Complex Relation Between Alcohol and Sexual Assault
• Noon Tuesday in the White PDR: Bowie, Mickey, and the NFL: Copyright in the 21st century (copies of the reading outside Sam's office)
• 7:30 pm Tuesday in ARH 131 - Funding for unfunded internships
• Thursday at 4:15 in 3821 - Life After Grinnell (for CS students)
• Anything in next week's Carnival and Creativity series

Peer

• Track and Field February 13.
• Love Notes. If the $2 is a stretch, Sam will pay. Email JS the elder.

Regular Peer

• Social Dance Workshop Tuesdays 7:00-8:00 in Bucksbaum Dance Studio (starting this week)
• Pun club Saturdays at 4pm in Younker (max 2)
• Socrates Cafe' Saturdays (max 2) email [socratescafe] to be added to the mailing list to hear about the top secret meeting location
• Electronic Potpourri on KDIC Fridays at Five
• Wednesday, 7:30, ARH 120, Environmental Movie

No Extra Credit, But Still Good

• High School Large Group Speech Presentations Saturday at 6:30 p.m. (I think) at the high-school auditorium.

Quiz

(define fave (irgb 250 0 42))
(define fave2 (irgb-lighter (irgb-darker fave)))
(irgb-complement fave)

• The way we express values is important, so "250/0/42" (that's for (irgb->string fave).
• (irgb-complement fave) does not change fave; it just computes a new color

The last problem: Write a procedure that adds 32 to each component.

Three possible strategies:

• lambda.
• section.
• compose.

We need to use compose.

(define irgb-much-lighter (compose irgb-lighter irgb-lighter)) ; not allowed
(define irgb-much-lighter (compose irgb-redder irgb-greener irgb-bluer))
(define irgb-much-lighter (compose irgb-complement irgb-darker irgb-darker irgb-complement))

Similar questions were in the mentor sessions and in the notes. (And no, we did not intend to give a particular advantage to those folks.)

Questions

Can we write define in the middle of a procedure?

No.

Did you even look at what you wrote for problem 4?

I thought so. I'll fix it during class.

How much info should we provide when citing other groups?

Approximately: "I talked to Tulah's Two Taylors about problem 4 and they provided me with advice on it."

How should we cite code from the assignment?

I don't require you to cite code from assignments.

If you choose to cite such code, use something like "Taken from assignment 3 at http://www.cs.grinnell.edu/~rebelsky/Courses/CSC151/2016S/assignments/assignment.03.html."

Or

    Curtsinger, C., Davis, J., Rebelsky, S. A., and Weinman, J. (2016).
    _Assignment 3: Color Transformations and Image Filters._  Grinnell
    College, Dept. of CS.  Online document at
    <http://www.cs.grinnell.edu/~rebelsky/Courses/CSC151/2016S/assignments/assignment.03.html>, last modified 2016-02-01; visited yesterday.

How can we wrap around given that the remainder function doesn't take decimals?

Option 1: Round to the nearest integer.

Option 2: Use a more clever calculation.

More about procedures

(define square (lambda (num) (* num num)))

(define square (lambda (renn) (* renn renn)))

(define square (lambda (color) (* color color)))

Scheme doesn't care what you call your parameters! So choose a name that makes sense to your human reader.

Be careful about what you name your parameters, as they can override existing names.

(define square
  (lambda (*)
    (* * *)))

(define square
  (lambda (+)
    (* + +)))

Ugh.

Lab, continued

Writeup: 3 ab and 5

Questions and reflection