--- title: Eboard 33 Association lists number: 33 section: eboards held: 2017-11-15 --- CSC 151.03, Class 33: Association lists ======================================== _Overview_ * Preliminaries * Notes and news * Upcoming work * Extra credit * Questions * Mentor evaluations * Lab * Debrief ### News / Etc. ### Upcoming Work * No reading for Friday. Work on your projects. * [Writeup for class 32](../writeups/writeup32) due TODAY at 10:30 p.m. * Exercise 6 * To: * Subject: CSC 151.01 Writeup 32 (YOUR NAMES) * [Writeup for class 33](../writeups/writeup33) due Friday at 10:30 p.m. * Exercises 4b and 4c. No documentation is required. * To: * Subject: CSC 151.01 Writeup 33 (YOUR NAMES) * Exam 3 cover pages due NOW! * Did you put your number on the sheet? * Did you sign both statements (if you feel comfortable doing so)? * Did you date both statements? * Did you remove the ra-cha-fringies if you removed the paper from a notebook? * Exam 3 Epilogues due TONIGHT! * One of the best comments so far: "This would have been much easier if I did the self-check problems every day." * Quiz Friday! * Association lists, algorithm efficiency, maybe trees * Mentor sessions tonight at 8pm, tomrrow at 7pm and 8pm. ### Extra credit (Academic/Artistic) * Pub-free quiz at Bob's. TONIGHT 9pm (I think). Stats-Math focus. * Convocation Thursday at 11 a.m. in JRC 101. "Work's Provocative Future: Which Graduates Will Thrive?" * Social Media in the U.S. and China, Thursday, Nov. 16, 7-9pm JRC 2nd. Chinese snacks provided. ### Extra credit (Peer) * "The First Time I Walked on the Moon". Four, count 'em, four performances. Thursday at 7:30, Friday at 7:30, Saturday at 7:30, Sunday at 2:00. * "You've got to pay attention to what's going on." * Orchestra, Saturday at 2pm ### Extra credit (Misc) ### Other good things * Fresh Flutes Thursday * Voice recitals Friday at 4:15 (Henderson) and 7:00 (Manuel) * Women's Basketball vs. Emmaus TONIGHT at 5:00 p.m. * Men's Basketball vs. Emmaus TONIGHT at 7:00 p.m. * Swimming and Diving Saturday at 1:00 p.m. ### Questions When should I turn a list into a vector? : If, for example, you don't expect to change the length and you are doing a lot of calls to list-ref. What did that mean? : I have a list, like '("Scooby Doo" "Shaggy" "Velma" "Fred" "Daphne" "Scrappy Doo" "The Van") : If it seems like I'm doing things like `(list-ref best-show-ever 4)` I'm probably better off turning it into a vector. `vector-ref` is much faster than `list-ref`. : If it seems like characters are being added, `(cons "Another Zombie" best-show-every)``, I don't want a vector. Best show ever, really? : No. How does the vector procedure turn its elements into a vector? : Magic. Explain: "Some of you may recall that we said that "`if` can take a value other than #t or #f. Here's an example why." : The nearby code looks something like the following. ``` (let ([result (assoc "Scooby" tv-shows)]) (if result (cadr result) #f)) ``` When would you want to turn a vector into a list? : Most frequently, when you want to use one of the handy-dandy list procedures we have already, like `filter`. Can I redefine a variable within a procedure? : Yes, but that practice is usually discouraged because it may confuse the reader ``` (define my-proc (lambda (val) (let ([+ -]) (+ val 2)))) ``` Mentor and tutor evaluations ---------------------------- * Goal: Improve our program Lab --- Writeup is 4b and 4c. Can we make up the cartoon characters and sidekicks? : Sure. : `("Zandy Proton" "Sky Rebel")` : `("UM, the Ulimate Mentor" "UH, the Ultimate Helper")` What should `multi-assoc` return in the base case? : "`multi-assoc` returns a list of matching entries" : So it should return a list. : What list is appropriate? Do you have hints for writing `multi-assoc`? : Don't call `assoc`. : Look at the pattern we have for recursing over a list. (Or how `assoc` is defined.) Debrief -------