Overview

• Preliminaries.
  • Admin.
  • Upcoming Work.
  • Extra Credit.
  • Questions.
• Quick summary.
• Lab.

Preliminaries

Admin

• Continue partners!
• Reminder: If you meet with me for TMTL, please make sure to bring your exam and to have read through the answer key.
• Review sessions this week:
  • Wednesday, 8pm (Caleb)
  • Thursday, 10am (SamR)
  • Thursday, 8pm (Erin)

Upcoming Work

• Project Pictures: NOW!
• Projects: Next Tuesday at 10:00 a.m.
• Reading for Wednesday (some parts will be familiar): Files in Scheme
• Today's Lab writeup (due before class Friday)
  • Email to grader-151-01@cs.grinnell.edu
  • Subject: CSC 151 Lab Writeup Class 43 (Your Names)
  • Exercises: 5 and 6

Extra Credit Opportunities

• If possible, send me these in advance.
• Note: You don't get extra credit for supporting yourself.

Academic

• Any visit to the current show in the Faulconer gallery.
• Learning Deconstructed Workshop Series, Tuesdays at 11 in JRC 209.
• CS Table TODAY: Social Media and Emergency Response
• Scholars' Convocation Thursday: Cosmic Secrets: Soviet Space Exploration, Censorship, and the Cold War.
• Metropolitan Opera Simulcast, November 21, 11:30 a.m. Lulu by Berg, Harris Cinema.

Peer Support

• Translations (a play). 7:30 p.m. Thursday through Saturday, 2:00 p.m. Sunday. Tickets at the Box Office.

Miscellaneous

• Noontime rally, Thursday, in support of the Missouri students and of our own students of color.

Regular Peer Support

• Pals of PALS, pals@grinnell.edu, normally Saturday at 7:45 am (breakfast included; felines only), and Mondays at 4:45. Requires sign up in advance. MORE HELP NEEDED!
• Socrates Cafe', Saturdays, Younker, 2pm.
• Pun Club, Saturdays, 4pm, Way over Younker.

Upcoming Peer Support

• Women's Basketball vs. Beloit, Nov. 28 at 3:00 p.m.
• Women's Basketball vs. St. Norbert, Dec. 5 at 3:00 p.m.
• One-act Festival Dec. 5 & 6.
• Women's Basketball vs. Carroll, Dec. 12 at 3:00 p.m.

Other Good Things (No Extra Credit)

• Jazz Band Wednesday
• Latin-American Ensemble Thursday
• Swim Meet Saturday

Questions

Quick Summary

• Higher-order procedures are procedures that take other procedures as parameters or return other procedures as values.
  • Some are built-in
  • Some you define yourself
• Turtle script was an example from the exam.
• What are some of the built-in ones we've used this semester?
  • (repeat NUM PROC) or (repeat NUM PROC VAL)
    • In the first case, the procedure has no parameters
  • (for-each PROC LIST)
  • (image-variant IMAGE PROC)
  • (map PROC LIST)
  • (image-compute TWO-PARAMETER-PROC WIDTH HEIGHT)
    • The procedure needs to take two integers and return an integer-encoded RGB color
  • (apply PROC LIST) - a new one
  • (any PRED? LIST) and (all PRED? LIST).
• Four of these generally return procedures
  • (section PROC ...)
  • (l-s PROC VAL)
    • Must be a binary procedure
  • (r-s PROC VAL)
  • (compose PROC PROC) and (o PROC PROC)
• When you pass in the procedure, you can pass in both a named procedure and an anonymous procedure.

• How do you write a procedure that returns a procedure?

  (define function
    (lambda (params)
      ...
      (lambda (other-params) ; THIS IS WHAT YOU ARE RETURNING
         instructions )))
  

Questions, Revisited

Can we write map together?

    (define my-map
      (lambda (proc lst)
        (if (null? lst)
            null
            (cons (proc (car lst))
                  (my-map proc (cdr lst))))))

Lab

Writeup: 5 and 6