rust-slices.txt

rust-slice-panics.rs

fn main() {
    let mut s = String::from("hello world");
    let len = first_word(&s);
    {
    	let word = &s[0..len];
    	println!("word is {}", word); // word is hello
    }
    s.clear();
    let word = &s[0..len]; // thread 'main' panicked at 'byte index 5 is out of bounds of ``', src/libcore/str/mod.rs:2144
    println!("word is {}", word);
}

fn first_word(s: &String) -> usize {
    let bytes = s.as_bytes();

    for (i, &item) in bytes.iter().enumerate() {
        if item == b' ' {
            return i;
        }
    }

    s.len()
}

rust-slice.rs

fn main() {
    let mut s = String::from("hello world");
    let len = first_word(&s);
    // let word = s[0..len]; // `str` does not have a constant size known at compile-time
    let word = &s[0..len];
    println!("word is {}", word);

    // s.clear(); // Error! mutable borrow occurs here and let word = &s[0..len] is immutable
}

fn first_word(s: &String) -> usize {
    let bytes = s.as_bytes();

    for (i, &item) in bytes.iter().enumerate() {
        if item == b' ' {
            return i;
        }
    }

    s.len()
}