What's the best way to compare 2 vectors or strings element by element?

Question

What's the best way to compare 2 vectors or strings element by element in Rust, while being able to do processing on each pair of elements? For example if you wanted to keep count of the number of differing elements. This is what I'm using:

let mut diff_count: i32 = 0i32;
for (x, y) in a.chars().zip(b.chars()) {
    if x != y {
        diff_count += 1i32;
    }
}

Is that the correct way or is there something more canonical?

Answer 1

To get the count of matching elements, I'd probably use filter and count.

fn main() {
    let a = "Hello";
    let b = "World";

    let matching = a.chars().zip(b.chars()).filter(|&(a, b)| a == b).count();
    println!("{}", matching);

    let a = [1, 2, 3, 4, 5];
    let b = [1, 1, 3, 3, 5];

    let matching = a.iter().zip(&b).filter(|&(a, b)| a == b).count();
    println!("{}", matching);
}

Answer 2

If you wanted to use @Shepmaster's answer as the basis of an assertion to be used in a unit test, try this:

fn do_vecs_match<T: PartialEq>(a: &Vec<T>, b: &Vec<T>) -> bool {
    let matching = a.iter().zip(b.iter()).filter(|&(a, b)| a == b).count();
    matching == a.len() && matching == b.len()
}

Of course, be careful when using this on floats! Those pesky NaNs won't compare, and you might want to use a tolerance for comparing the other values. And you might want to make it fancy by telling the index of the first nonmatching value.