# Week 02 Laboratory Exercises

### Objectives

• To practice using Rust's basic collection tyoes
• Exposure to simple derive macros
• Understand and use Rust's error handling philosopy, and the try trait

### Activities To Be Completed

The following is a list of all the activities available to complete this week...

• Tribonacci
• My Caesar
• To Upper (Investigating strings!)
• Collections
• Data analysis

### Preparation

Before the lab you should re-read the relevant lecture slides and their accompanying examples.

### Getting Started

Create a new directory for this lab called lab02, change to this directory, and fetch the provided code for this week by running these commands:

mkdir lab02
cd lab02
6991 fetch lab 02

Or, if you're not working on CSE, you can download the provided code as a tar file.

### Exercise: Tribonacci

In this task, you will write a function that computes a variable number of Tribonacci numbers , and also their sum.

Your program should read a single integer, n, from the command-line arguments, and subsequently compute the first n Tribonacci numbers, along with their sum.

If no command-line arguments are given, you should assume the value of n to be 10.

Invalid input should be handled by returning a custom error message "Please enter a valid size!" through the struct TribonacciError, and then subsequently exiting the program.

Your program need only be able to calculate from n = 3 to n = 145 inclusive. Note that n = 145 produces very large numbers that increase far past the width of a i64 type. You may want to (strongly) consider using one of i128 or u128 instead, both of which can fit the largest number in that sequence.

6991 cargo run -- 4
Finished dev [unoptimized + debuginfo] target(s) in 0.00s
Running target/debug/tribonacci 4
Values: [1, 1, 1, 3]

Sum: 6
6991 cargo run -- 10
Finished dev [unoptimized + debuginfo] target(s) in 0.00s
Running target/debug/tribonacci 10
Values: [1, 1, 1, 3, 5, 9, 17, 31, 57, 105]

Sum: 230
6991 cargo run -- -1
Finished dev [unoptimized + debuginfo] target(s) in 0.00s
Running target/debug/tribonacci -1
Error: Please enter a valid size


When you think your program is working, you can use autotest to run some simple automated tests:

6991 autotest


When you are finished working on this exercise, you must submit your work by running give:

6991 give


You must run give before Week 3 Wednesday 21:00:00 to obtain the marks for this exercise. Note that this is an individual exercise; the work you submit with give must be entirely your own.

### Exercise: My Caesar

In this activity, your task is to write a program that encrypts a message using a Caesar cipher.

The program should read in a single command-line argument, which is the number of positions to shift each letter (i32). If there is no command-line argument, or if the argument is not a number, the program should use a default shift of 5.

The program should then iterate over each line of standard input, shifting each letter by the specified number of positions. The shifted line should then be printed to standard output.

However, only letters of the alphabet (i.e. 'A'..='Z', 'a'..='z') should be shifted. All other characters should be printed as-is.

Shifted letters should wrap around the alphabet, so that 'A' shifted by 1 becomes 'B', 'Z' shifted by 1 becomes 'A', 'y' shifted by 3 becomes 'b'.

If the provided shift is negative, you should treat the shift as operating in the opposite direction.

For example, 'A' shifted by -1 becomes 'Z', 'Z' shifted by -1 becomes 'Y', 'b' shifted by -3 becomes 'X'.

A shift of 0 should not modify the input text at all.

For example:

6991 cargo run
Finished dev [unoptimized + debuginfo] target(s) in 0.00s
Running target/debug/my_caesar
hello!
Shifted ascii by 5 is: mjqqt!
Dr. Taylor Swift is the worlds greatest musician!
Shifted ascii by 5 is: Iw. Yfdqtw Xbnky nx ymj btwqix lwjfyjxy rzxnhnfs!

6991 cargo run -- 10
Finished dev [unoptimized + debuginfo] target(s) in 0.00s
Running target/debug/my_caesar
And I know it's long gone and 👋 That magic's not here no more 😭🫀🇧​🇷​🇪​🇦​🇰
Shifted ascii by 10 is: Kxn S uxyg sd'c vyxq qyxo kxn 👋 Drkd wkqsm'c xyd robo xy wybo 😭🫀🇧​🇷​🇪​🇦​🇰
T_T crying
Shifted ascii by 10 is: D_D mbisxq


When you think your program is working, you can use autotest to run some simple automated tests:

6991 autotest


When you are finished working on this exercise, you must submit your work by running give:

6991 give


You must run give before Week 3 Wednesday 21:00:00 to obtain the marks for this exercise. Note that this is an individual exercise; the work you submit with give must be entirely your own.

### Exercise: To Upper (Investigating strings!)

This activity is an investigation of Rust's strings!

You have been provided a simple crate, to_upper, which does not compile! Your task is to modify to_upper/src/main.rs so that it takes in a single command-line argument and converts the appropriate characters to uppercase. It may help to RTFC!

6991 cargo run -- "hello world!!!"
Finished dev [unoptimized + debuginfo] target(s) in 0.00s
Running target/debug/to_upper 'hello world'\!''\!''\!''
arg = "hello world!!!"
upp = "HELLO WORLD!!!"
6991 cargo run -- "uwu🥺👉👈"
Finished dev [unoptimized + debuginfo] target(s) in 0.00s
Running target/debug/to_upper 'uwu🥺👉👈'
arg = "uwu🥺👉👈"
upp = "UWU🥺👉👈"


When you think your program is working, you can use autotest to run some simple automated tests:

6991 autotest


When you are finished working on this exercise, you must submit your work by running give:

6991 give


You must run give before Week 3 Wednesday 21:00:00 to obtain the marks for this exercise. Note that this is an individual exercise; the work you submit with give must be entirely your own.

### Exercise: Collections

Rust's collection types could be generally categorised into four groups:
• Sequences
• Vec
• VecDeque
• LinkedList
• Maps
• HashMap
• BTreeMap
• Sets
• HashSet
• BTreeSet
• Misc.
• BinaryHeap

In this activity, we'll be exploring the performance of first three (Vec, VecDeque, and LinkedList), and HashMap collections.

For each of the four collections above, your code should:

• Create a new instance of the collection.
• Add some MAX_ITER elements to it.
• Remove MAX_ITER elements from it.
• Time each of the above operations.

Before you start, please write down some of your expectations about what you think will be the most performant collection for these operations.

The analysis of Vec and VecDeque has already been completed for you in the provided code.

This exercise also contains a theory section. At the end of your main function, you should write a comment that answers the following questions:

• Which collection type was the fastest for adding and removing elements?
• Why do you think this was the case?
• Is there any significant difference between Vec and VecDeque deletion?
• If so, why? If not, why not?
• When would you consider using VecDeque over Vec?
• When would you consider using LinkedList over Vec?
• Did the results suprise you? Why or why not?.
The above will be manually marked. There will be an opportunity to discuss this with a tutor and get marked during your week 4 workshop. If you cannot attend, your work will instead be manually marked (offline) during week 5.

When you are finished working on this exercise, you must submit your work by running give:

6991 give


You must run give before Week 3 Wednesday 21:00:00 to obtain the marks for this exercise. Note that this is an individual exercise; the work you submit with give must be entirely your own.

### Exercise: Data analysis

In this exercise, you are taking on the role of a prospective data analyst and have gotten your hands on a dataset of (fictional!) CSE enrolments.

The dataset is in the file enrolments.psv and each row contains the following columns (in order):

• UNSW Course Code
• UNSW Student Number
• Name
• UNSW Program
• UNSW Plan
• WAM
• UNSW Session
• Birthdate
• Sex

Each row of data represents one enrolment. One student may have multiple rows, as they may be enrolled in multiple courses.

You've been asked to process the data, and output answers to the following questions:

1. How many unique students are there?
2. What is the most common course (with how many students)?
3. What is the least common course (with how many students)?
4. What is the average WAM of all students in CSE (to 2 decimal places)?
5. Given a specific student number, output their details?

Note that you can assume that there will be no two equally most-common or equally least-common courses in the dataset -- i.e. there will always be exactly one answer.

 6991 cargo run
Finished dev [unoptimized + debuginfo] target(s) in 0.01s
Running target/debug/data_analysis
Number of students: 8065
Most common course: COMP1511 with 953 students
Least common course: BIOM9002 with 1 students
Average WAM: 61.94
Enter a student id: 5231508
== STUDENT FOUND ==
Name: Xu, Michael Rahul
Program: 7003/1
Plan: COMPSS
WAM: 75.09
Session: 22T2
Birthdate: 20010410
Sex: M


6991 cargo run
Finished dev [unoptimized + debuginfo] target(s) in 0.50s
Running target/debug/data_analysis
Number of students: 8065
Most common course: COMP1511 with 953 students
Least common course: BIOM9002 with 1 students
Average WAM: 61.94
Enter a student id: abcd


When you are finished working on this exercise, you must submit your work by running give:

6991 give


You must run give before Week 3 Wednesday 21:00:00 to obtain the marks for this exercise. Note that this is an individual exercise; the work you submit with give must be entirely your own.

### Submission

When you are finished each exercise make sure you submit your work by running give.

You can run give multiple times. Only your last submission will be marked.

Don't submit any exercises you haven't attempted.

If you are working at home, you may find it more convenient to upload your work via give's web interface.

Remember you have until Week 3 Wednesday 21:00:00 to submit your work.

You cannot obtain marks by e-mailing your code to tutors or lecturers.

Automarking will be run several days after the submission deadline, using test cases different to those autotest runs for you. (Hint: do your own testing as well as running autotest.)

After automarking is run you can view your results here.

#### Lab Marks

When all components of a lab are automarked you should be able to view the the marks via give's web interface or by running this command on a CSE machine:

6991 classrun -sturec