Feature Request: zip_pad_with_default

[abrassel]

When trying to zip over two iterators of unequal lengths, zip_longest is very useful for the case in which one doesn't exist.
When trying to do zip longest, but the underlying items implement Default, it could be useful to have a version of zip_longest that pads the shorter iterator with Item::default().

[scottmcm]

I don't think a new iterator adapter is the best choice here, since that's a relatively heavy and non-orthogonal addition.

The item type for zip_longest is EitherOrBoth, though, so maybe add some methods on there to make things easier?

As a sketch,

impl<T:Default> impl EitherOrBoth<T> {
    fn or_default(self) -> (T, T) { ... }
}

Then .zip_pad_with_default() could be done as just .zip_longest().map(|x| x.or_default()).

(Dunno what the best name for the method would be. I'm inspired here by https://docs.rs/itertools/0.9.0/itertools/enum.MinMaxResult.html#method.into_option)

[abrassel]

That looks great to me! I've not contributed to an open source project before - at this point do I submit a pull request?

[phimuemue]

That looks great to me! I've not contributed to an open source project before - at this point do I submit a pull request?

I think you could give it a try.

[jswrenn]

Please do! I'd be happy to merge this.

[abrassel]

@jswrenn Done!