How do I create an iterator over an array which takes values from index i and i+1?

Question

I created a small example that runs in the Rust Playground:

#[derive(Clone)]
pub struct Person {
    pub firstname: Vec<u8>,
    pub surname: Vec<u8>,
}

fn main() {
    let p0 = Person {
        firstname: vec![0u8; 5],
        surname: vec![1u8; 5],
    };
    let p1 = Person {
        firstname: vec![2u8; 7],
        surname: vec![3u8; 2],
    };
    let p2 = Person {
        firstname: vec![4u8; 8],
        surname: vec![5u8; 8],
    };
    let p3 = Person {
        firstname: vec![6u8; 3],
        surname: vec![7u8; 1],
    };

    let people = [p0, p1, p2, p3];

    for i in 0..people.len() {
        if i + 1 < people.len() {
            println!(
                "{:?}",
                (people[i].firstname.clone(), people[i + 1].surname.clone())
            )
        }
    }
}

Given the array people, I want to iterate its elements and collect tuples of the first name of the person at index i and the surname of the person at index i+1. This simple for loop does the job, but let's assume that instead of println I would like to pass such tuple into some function f. I can easily do this in this for loop, but I would like to learn whether I can implement that using an iterator iter() (and later apply collect() or fold functions if needed) instead of using the for loop?

score 2 · Answer 1 · edited Dec 09 '19 at 15:21

You can combine two features:

Create an array iterator that skips the first elements (iter().skip(1)).
Iterator.zip

#[derive(Clone)]
pub struct Person {
    pub firstname: Vec<u8>,
    pub surname: Vec<u8>,
}

fn main() {
    let p0 = Person {
        firstname: vec![0u8; 5],
        surname: vec![1u8; 5],
    };
    let p1 = Person {
        firstname: vec![2u8; 7],
        surname: vec![3u8; 2],
    };
    let p2 = Person {
        firstname: vec![4u8; 8],
        surname: vec![5u8; 8],
    };
    let p3 = Person {
        firstname: vec![6u8; 3],
        surname: vec![7u8; 1],
    };

    let people = [p0, p1, p2, p3];

    for (i, j) in people.iter().zip(people.iter().skip(1)) {
        println!("{:?}", (&i.firstname, &j.surname));
    }
}

Permalink to the playground

Shepmaster · Answer 2 · 2019-12-09T15:21:22.990

2

I would use slice::windows:

for window in people.windows(2) {
    println!("{:?}", (&window[0].firstname, &window[1].surname))
}

How do I create an iterator over an array which takes values from index i and i+1?

2 Answers2