FahrenheitToCelsius/src/main.rs

use std::io::stdin;

fn convert_to_c(temp: f32) -> f32 {
    //subtracting 32 from the input
    let mut celsius = temp - 32_f32;
    //Defining what 5/9 is, then multiplying the input-32
    const FIVE_DIV_NINE: f32 = 5.0 / 9.0;
    celsius *= FIVE_DIV_NINE;
    celsius
}

fn convert_to_f(temp: f32) -> f32 {
    //Defining what 5/9 is, then deviding the input by it and adding 32
    const FIVE_DIV_NINE: f32 = 5.0 / 9.0;
    let mut fahrenheit = temp / FIVE_DIV_NINE;
    fahrenheit += 32_f32;
    fahrenheit
}

fn main() {
    println!("Fahrenheit <--> Celsius converter");
    println!("Press \"^C\" to end the program");
    println!("Enter your number immidiatly followed by an F or C");
    loop {
        let mut input = String::new();
        println!("Please input the temperature");
        stdin()
            .read_line(&mut input)
            .expect("Failed to read line");
        let input = input.trim();
        /*
        Split the input into two strings. Input, which contains the number;
        and System, which contains if it is celcius or fahrenheit
        */
        let (input,system) = input.split_at(input.len() - 1);
        //If the input in a number, output it, else, restart loop
        let input: f32 = match input.parse() {
            Ok(num) => num,
            Err(_) => continue,
            };
        /*
        If the system is known, call the convert function, 
        otherwise repeat loop
        */
        match system {
            "C" => println!("{}°C is {:.2}°F", input, convert_to_f(input)),
            "F" => println!("{}°F is {:.2}°C", input, convert_to_c(input)),
            _ => continue,
        };
    }
}