[Rust] Create a loop in Rust

This lesson shows how to use a Rust loop to run a program infinitely.

use std::io;
use std::process;

fn main() {
    loop {
        println!("Please enter a first number: ");
        let a = read_user_input();
    
        println!("Please enter a second number: ");
        let b = read_user_input();
    
        let result = sum(a, b);
        println!("{} + {} = {}", a, b, result);
    }
}

fn sum(a: u32, b: u32) -> u32 {
    a + b
}

fn read_user_input() -> u32 {
    let mut input = String::new();
    io::stdin().read_line(&mut input).unwrap();
    
    let digit:u32;
    
    match input.trim().parse() {
        Ok(val) => digit = val,
        Err(_err) => {
            println!("Not a valid number!");
            process::exit(1);
        }
    };
    
    digit
}