--- title: Eboard 11 Boolean values, predicate procedures, and list filters number: 11 section: eboards held: 2017-09-18 --- CSC 151.01, Class 11: Boolean values, predicate procedures, and list filters ============================================================================= _Overview_ * Preliminaries * Notes and news * Upcoming work * Extra credit * Questions * Notes from quiz 3 * Lab * Debrief ### News / Etc. * New partners. * Please switch driver and navigator after every problem. * Please make sure to return your computer cards to the jar. * Thank you for all of the excellent exam questions. You will find many Q&A in the exam. * I did not have time to finish grading your quizzes this weekend. We will still go over them to help you understand what I expect for documentation and tests. ### Upcoming Work * [Writeup for class 10](../writeups/writeup10) due TONIGHT at 10:30 p.m. * Exercise 6 * To: * Subject: CSC 151.01 Writeup 10 (YOUR NAMES) * [Writeup for class 11](../writeups/writeup11) due Wednesday at 10:30 p.m. * Exercise 4c * To: * Subject: CSC 151.01 Writeup 11 (YOUR NAMES) * Read: [Local bindings](../readings/local-bindings) for Wednesday's class. * Read: [A computer scientist's perspective of data science](../readings/data-science) for Wednesday's class [Should be ready late tonight]. * Exam 1 * Exam due TOMORROW night * Cover sheet due Wednesday in class * Epilogue due Wednesday night ### Extra credit (Academic/Artistic) * CS Table, Tuesday at noon in PDR A: Activism * CS Extras, Thursday at 4:15 in 3821, Study Abroad ### Extra credit (Peer) * Women's soccer, Saturday * Women's soccer, Sunday ### Extra Credit (Misc) _None at the moment._ ### Other Good Things ### Exam questions Can you give me a hint on problem 2? : Don't use `substring` : In the lab in which we had 42,000 things to deal with, I asked you to find the middle 5. How did you do that? On problem 1, do we have to support complex numbers as input? : Yes. How do I generate a random six digit number? : `(random 1000000)` How do I submit my exam? : Name it 012345.rkt (substituting your random number) : Send it to as an attachment in an email message entitled "CSC 151.01 Exam 1" (or something similar) Can you explain the parameters to sublist? : Starting position (inclusive) and ending position (exclusive), just like in `substring` Can I use the `sublist` procedure I wrote in problem 2 for problem 5? : Sure. Can I use `string-length`? : Sure. How should we write our examples or tests? : You know how to write tests. : Examples you will generally run in the interactions pane and then copy and paste the input/output to the definitions pane and then comment it out. Notes from quiz 3 ----------------- ### Part a: Documenting nearest multiple ``` ;;; Procedure: ;;; nearest-multiple ;;; Parameters: ;;; val, a real ;;; n, a real ;;; Purpose: ;;; Find a multiple of n that is nearest to val. ;;; Produces: ;;; m, a real - a multiple of n ;;; Preconditions: ;;; n is not zero ;;; Postconditions: ;;; * m is a multiple of n. That is, m/n is an integer. (Alternately, ;;; the remainder of m/n is 0.) (There exists an integer i, such that ;;; m = i*n) ;;; * m is a nearest multiple of n to val. That is, for all other ;;; multiples of n, h, the |h - val| >= |m - val| ``` * Don't rename the parameters to meaningless things, such as `value1` and `value2` * If you do want to rename them, choose more meaningful names. * We *always* name the result in the Produces section. * We *always* give a type in the Produces section * We *might* add an additional note in the Produces section * If we don't know what a multiple is, we might say "7 is a multiple of 2 because when I multiply 2 by 3.5 I get 7." * the distance of h to val is no smaller than distance of m to val. By "distance" we mean the absolute value difference between the two values. * Sam would call `n` an integer, but it's up to you. * What's the nearest multiple of 4 to 10? (`val` is 10, `n` is 4) ### Part b: Testing * Different tests! (That is, test different concepts) * Make sure that your tests test valid inputs and outputs. * If there are two nearest multiples, don't assume one. * If zero is not a valid `n`, don't use it as `n`. Lab and Debrief --------------- How should I compare the two-letter state abbreviation to "IA"? : `=` - **No**. They are not numbers. `=` is for numbers : `eq?` - **No**. `eq?` does not always work the way you expect for strings. : `eqv?` - **No**. `eqv?` does not always work the way you expect for strings. : `equal?` - Yes. `equal?` works well as your default comparison. : `string=?` - Yes. You know that they are strings. : `string-ci=?` - Yes. And this is nice because it supports `"ia"`. Can I write a lambda-free solution to `in-iowa?` : Sure. : First we extract the state. `(section list-ref <> 4)`. : Next we compare to "IA". `(section string-ci=? <> "IA")`. : So we can just compose those two. `(o (section list-ref <> 4) (section string-ci=? <> "IA"))` Is there an easy way to write "between a and b"? : `(section < a <> b)` How do I figure out if any city in IA lacks a longitude? : `(filter (negate has-longitude) (filter in-iowa? zips))`