Tracking Issue for `Iterator::intersperse`

[camelid]

This is a tracking issue for the Iterator::intersperse and intersperse_with methods. It is based on itertools::intersperse and is the iterator equivalent of Vec::join.

The feature gate for the issue is #![feature(iter_intersperse)].

Public API

// core::iter

pub trait Iterator {
    fn intersperse(self, separator: Self::Item) -> Intersperse<Self>
    where
        Self: Sized,
        Self::Item: Clone;

    fn intersperse_with<G>(self, separator: G) -> IntersperseWith<Self, G>
    where
        Self: Sized,
        G: FnMut() -> Self::Item;
}

#[derive(Debug, Clone)]
pub struct Intersperse<I: Iterator> where I::Item: Clone {}

impl<I> Iterator for Intersperse<I> where I: Iterator, I::Item: Clone {
    type Item = I::Item;
}

pub struct IntersperseWith<I, G> where I: Iterator {}

impl<I, G> Debug for IntersperseWith<I, G> where I: Iterator + Debug, I::Item: Debug, G: Debug {}

impl<I, G> Clone for IntersperseWith<I, G> where I: Iterator + Clone, I::Item: Clone, G: Clone {}

impl<I, G> Iterator for IntersperseWith<I, G> where I: Iterator, G: FnMut() -> I::Item {
    type Item = I::Item;
}

Steps / History

• Implement intersperse: Add Iterator::intersperse #79479
• Add intersperse_with: Add Iterator::intersperse_with #80567
• FCP
• Stabilization PR: Stabilize Iterator::intersperse() #88548
  (UPDATE: stabilization was reverted because there was a lot of breakage: Stabilizing Iterator::intersperse breaks a large number of crates #88967)
• Determine how to avoid breakage and un-revert
• Add impl<I: FusedIterator> FusedIterator for Intersperse<I>? (Can be added after stabilization, so not urgent.)

Unresolved Questions

None.

[m-ou-se]

#80567 is adding intersperse_with to this feature.

[cyqsimon]

I would like to suggest a simpler, alternative name for this method - weave. At the time of comment, the word weave is not yet used in Rust std.

Intersperse is quite verbose (especially when compared to Vec::join), but more importantly rarely used in common English. weave is much more common and concise in comparison.

[ibraheemdev]

Scala and haskell both use intersperse. Scalaz calls it intercalate.

[tmplt]

I would like to suggest a simpler, alternative name for this method - weave.

weave is not on the list of terms I would search for when looking for the expected behavior. I'd even consider it vanity.

Intersperse is quite verbose (especially when compared to Vec::join), but more importantly rarely used in common English. weave is much more common and concise in comparison.

A verbose function name describes its effect better. More so if the term is uncommon; there is then less ambiguity. intersperse does exactly what is says: intersperse elements with a common separator.