How to join a sequence of tuples, each with its own sequence?

December 3, 2023

I have a sequence of tuples where each tuple contains another sequences.
To better illustrate the problem, please have a look at the below snippet (Rust Playground):

fn main() {
    let data = [
        (vec![1, 2, 3], vec!['a']), 
        (vec![4, 5, 6], vec!['b', 'c'])
    ];
    let res: (Vec<i32>, Vec<char>) = data...?

    // res = (vec![1, 2, 3, 4, 5, 6], vec!['a', 'b', 'c']);

}

I would like to iterate data only once to create two Vecs. Each Vec is a concatenation of all the elements within a corresponding tuple’s member.
res is a commented out expected result.

How this can be achieved in Rust?

>Solution :

You can use reduce.

let res: (Vec<i32>, Vec<char>) = data
    .into_iter()
    .reduce(|(mut acc1, mut acc2), (mut i1, mut i2)| {
        acc1.append(&mut i1);
        acc2.append(&mut i2);
        (acc1, acc2)
    })
    // An empty sequence will produce `(vec![], vec![])`
    .unwrap_or_default();