rust-book on jonah vairon

employee db

Tue, 24 Mar 2026 00:00:00 +0000

background

The final section of the eighth chapter of the rust book ends with some suggested exercises. The last of which is to write a program that:

Using a hash map and vectors, create a text interface to allow a user to add employee names to a department in a company; for example, “Add Sally to Engineering” or “Add Amir to Sales.” Then, let the user retrieve a list of all people in a department or all people in the company by department, sorted alphabetically.

pig latin

Fri, 20 Mar 2026 00:00:00 +0000

background

The final section of the eighth chapter of the rust book ends with some suggested exercises. The second of which is to write a program that:

Convert strings to Pig Latin. The first consonant of each word is moved to the end of the word and ay is added, so first becomes irst-fay. Words that start with a vowel have hay added to the end instead (apple becomes apple-hay). Keep in mind the details about UTF-8 encoding!

christmas carol

Wed, 18 Mar 2026 00:00:00 +0000

background

The final section of the third chapter of the rust book ends with some suggested exercises. The last of which is to write a program to: “Print the lyrics to the Christmas carol “The Twelve Days of Christmas,” taking advantage of the repetition in the song.”

solution

This was more fun that it looked. Especially trying to identify patterns in the lyrics.

Is this the most optimised version?

Probably not.

fibonacci

Wed, 18 Mar 2026 00:00:00 +0000

background

The final section of the third chapter of the rust book ends with some suggested exercises. The second of which is to write a program to: “Generate the nth Fibonacci number.”

solution

I’m not going to implement the best fibonacci implementation?. Just the bog standard recursive approach with no memoisation. Reusing the input code from the guessing game again:

use std::io;

fn main() {
    loop {
        println!("Which Fibonacci number would you like?");

        let mut n = String::new();

        io::stdin()
            .read_line(&mut n)
            .expect("Failed to read line");

        let n: i32 = match n.trim().parse() {
            Ok(num) => num,
            Err(_) => continue
        };

        let nth_fib = fib(n);

        println!("Fibonacci {n} is: {nth_fib}");
    }
}

fn fib(n: i32) -> i64 {
    if n == 0 {
        return 1;
    } else if n == 1 {
        return 1;
    } else {
        return fib(n-1) + fib(n-2);
    }
}

median and mode

Tue, 17 Mar 2026 00:00:00 +0000

background

The final section of the eighth chapter of the rust book ends with some suggested exercises. The first of which is to write a program that:

Given a list of integers, use a vector and return the median (when sorted, the value in the middle position) and mode (the value that occurs most often; a hash map will be helpful here) of the list.

solution

While straightforward on paper, calculating the median posed a bit of challenge with even lists of numbers. The problem being, when there’s no clear “middle” value the tendency is to take the mean of the 2 middle values. But, Rust being strongly typed, this meant potentially returning a float (i.e. f32) in a function that would otherwise return an integer (i.e. i32).

fahrenheit to celsius

Sun, 15 Mar 2026 00:00:00 +0000

background

The final section of the third chapter of the rust book ends with some suggested exercises. The first of which is to write a program to: “Convert temperatures between Fahrenheit and Celsius.”

solution

Reusing code from the guessing game chapter, we can read input, cast it to a 32 bit float through a type hint and perform the conversion:

use std::io;

fn main() {
    loop {
        println!("Degrees in Farenheit:");

        let mut degrees_f = String::new();

        io::stdin()
            .read_line(&mut degrees_f)
            .expect("Failed to read line");

        let degrees_f: f32 = match degrees_f.trim().parse() {
            Ok(num) => num,
            Err(_) => continue
        };

        let degrees_c = (degrees_f - 32.0) * 5.0/9.0;

        println!("is {degrees_c} degrees Celsius.");
    }
}