This lab completes our discussion git, and starts our first programming language, namely Racket.
For learning racket, we will mainly follow Functional Introduction to computer science
You may also find the BSL reference helpful.
At any point you can view the history of your changes using
$ git log
Use this command to verify that all the changes you expected to be pushed to the server really were.
If you also want to see complete diffs at each step, use
$ git log -p
Often the overview of the changes is useful to get a feel for each step
$ git log --stat --summary
In most projects, you have to share commit messages to (at least) the same people who view your source code. Share your "best commit" message with one or more of your neighbours.
Find something positive to say about the other commit messages you are reading.
Find a constructive improvement with one of the other messages. Don't be mean, people have varying levels of experience with this.
Form groups of 2 or 3.
Work through Exercise 0: for each of the following lines of code, someone from the group should guess what is wrong before trying it in the Interactions window of DrRacket.
(* (5) 3)
(+ (* 2 4)
(5 * 14)
(* + 3 5 2)
(/ 25 0)
Work through Exercise 1. In general where the text asks you to predict the value of an expression, you can also enter into the definitions window something like
(check-expect (* 6 9) 42)
When you run (e.g. F5), then you will find out if your prediction is correct.
Work through Exercise
2. You can test your answers by applying the following functions to appropriate arguments. Notice that the value of y does not matter.
#lang htdp/bsl
(define y 18)
(define (t1 x)
(or (= x 0) (< 0 (/ y x))))
(define (t2 x)
(or (< 0 (/ y x)) (= x 0)))
(define (t3 x)
(and (= x 0) (< 0 (/ y x))))
(define (t4 x)
(or (< 0 (/ y x)) (not (= x 0))))
Do this part on your own.
Do Exercise 4
Here are some tests to help you check your function
(check-expect (middle-of-three 1 2 3) 2)
(check-expect (middle-of-three 2 1 3) 2)
(check-expect (middle-of-three 1 3 2) 2)
Do these tests suffice? Why or why not?
(* (5) 3)
(+ (* 2 4)
(5 * 14)
(* + 3 5 2)
(/ 25 0)
Work through Exercise 1. In general where the text asks you to predict the value of an expression, you can also enter into the definitions window something like
(check-expect (* 6 9) 42)
When you run (e.g. F5), then you will find out if your prediction is correct.
Work through Exercise
2. You can test your answers by applying the following functions to appropriate arguments. Notice that the value of y does not matter.
#lang htdp/bsl
(define y 18)
(define (t1 x)
(or (= x 0) (< 0 (/ y x))))
(define (t2 x)
(or (< 0 (/ y x)) (= x 0)))
(define (t3 x)
(and (= x 0) (< 0 (/ y x))))
(define (t4 x)
(or (< 0 (/ y x)) (not (= x 0))))
copy arith.rkt, save it as
~/cs2613/labs/L03/arith.rkt and commit it.
run your arith.rkt in DrRacket; observe that the test fails
run your arith.rkt in the DrRacket Stepper. Notice that
after about 7 steps, we have reduced the test case to multiplication by zero which looks wrong. That means that the problem is
with the recursive (reduction) step.
Fix the a > 0 case of my-* to match the following
formula a * b = (a - 1) * b + b, while still using my-+
DrRacket should report "The test passed!" when you have it working. Commit this version of your code. Remember that git commit message quality counts in this course, so work on making commit messages.
Unit testing is an important part of programming, and has inspired something called test driven development.
This activity continues arith.rkt from the first half of the lab.
Under
Language -> Choose Language -> Show Details -> Dynamic Properties
enable
⊙ Syntactic test suite coverage
comment out the given test
run your code in DrRacket again
most likely you will have some code highlighted with orange text and black foreground. This means that code is not covered by your test suite. Uncomment the given test, and if needed add tests to cover each piece of uncovered code.
When you have complete test coverage, commit your code.
In this course, for all racket assignments you will lose marks if
you don't have complete test coverage.
Push your repo to coursegit.
If you have extra time, run the tests on the command line with raco
test arith.rkt
Read FICS unit 3
Read FICS unit 4