Trying to get my program to work

[What]

Heres my code:

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

fn main() {
    let number = rand::rng().random_range(0..=1292929);
    let mut guess = String::new();
    
    println!("guess the number");
    
    loop {
        io::stdin().read_line(&mut guess).expect("AAAAAAAAAHH");
        
        let guess: u32 = match guess.trim().parse() {
            Ok(num) => num,
            Err(_) => continue,
        };
        
        println!("you guessed THIS {number}");
        
        match guess.cmp(&number) {
            Ordering::Greater => println!("TOO BIG"),
            Ordering::Less => println!("TOO SMALL"),
            Ordering::Equal => {
                println!("YOU WIN!!");
                break;
            }
        }
        
    }
    
}

When i run it it works, i enter a number and it comes up with the right stuff but then when i go to guess another number nothing happens, its meant to go back to the start of the loop

[jofas]

Is this spam or does the snippet come from an online tutorial or something?^[1] I answered a question with almost the exact same code three months ago:

I'm new to rust, what's with this loop?

read_line appends to the buffer it takes as argument instead of overriding the buffer's contents. If you define guess outside of the loop, it will fill up with all the lines your user provides as input, including the newline characters at the end. So if I type 42 during the first iteration, guess will be "42\n". Then I type 43 during the second iteration and guess becomes 42\n43\n. This will make parsing guess as u32 fail. This doesn't happen when I create a new buffer during each iteration.

---

1. See answers below, I wasn't aware of the guessing game chapter of the Rust book ↩︎

[What]

Oh its from the rust book since im learning rust for the first time

[cod10129]

@jofas

does the snippet come from an online tutorial or something?

Programming a Guessing Game - The Rust Programming Language

---

To fix the code, either declare a new let mut guess = String::new() in each iteration of the loop, or write guess.clear() at the beginning of the loop to make sure the input is read into an empty buffer.

(jofas explains how using the same buffer doesn’t work in his linked post)

[What]

Thanks i firgot to put the guess variable in the loop oops

[conqp]

You don't need to do that. You just need to clear it at the beginning (or the end) of each loop.

[Ddystopia]

It's better to use unwrap/expect, as well as asserting your expectations, instead of silent errors, because you can get quick feedback and pinpoint the issue. It would've probably helped there too.