Nested iteration

[lnicola]

I suspect this comes up pretty often, but what's the best way to compute and group multiple results from each item in an iterator? Basically something like:

(1..5)
    .iter_into_par()
    .map(|x| (x, (0..x).iter_into_par().map(move |y| x * 10 + y)))
    .for_each(|(x, ys)| {
        dbg!((x, ys.collect::<Vec<_>>()));
    });

Or similarly, how to compute (f(x), g(x)) in parallel for every x in the input? zip might work, but it's not implemented yet.

[orxfun]

Hi @lnicola . First thanks a lot for reminding the missing zip implementation, created issue #118 .

For the first example though, I find myself often in a similar situation. Not specific to parallel computation, right? We often write input.iter().map(|x| (x, f(x)). I agree that this is a bit annoying.

First, do we know a better way in the sequential Iterator to express this computation?

Second, we can try to come up with an idea and implement it here if it feels right. I believe it would be a new function of the (parallel) iterator which is neither chain nor zip.