Modified Rust Book Guessing Game Query

Question

I modified the code from the Rust Book's Guessing Game Tutorial to make it a little shorter; for a slide. Alas, I've introduced a bug, and it no longer executes correctly: the first input works as expected, but subsequent entries now yield no feedback.

What is the best way to guard against this situation?

use std::io;
use std::cmp::Ordering;
use rand::Rng;

fn main() {
    println!("Guess the number!");

    let secret_number = rand::thread_rng().gen_range(1, 101);

    let mut guess = String::new();

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

        let guess: u32 = match guess.trim().parse() {
            Ok(num) => num,
            Err(_) => continue,
        };

        println!("You guessed: {}", guess);

        match guess.cmp(&secret_number) {
            Ordering::Less => println!("Too small!"),
            Ordering::Greater => println!("Too big!"),
            Ordering::Equal => {
                println!("You win!");
                break;
            }
        }
    }
}

Answer 1

read_line will append the line to buffer, so your guess will accumulate all the inputs include newline characters! Moving let mut guess = String::new(); inside the loop solves the problem:

fn main() {
    ...

    loop {
        let mut guess = String::new();

        ...
    }
}