Parsing a(ba)* in 1.0.0-alpha.4

[01mf02]

I am converting a parser from chumsky 0.9 to 1.0.0-alpha.4. During this, I noticed a pattern that I found quite nontrivial to translate. In particular, a parser for a(ba)*, where a and b are parsers that have the same output type T, and we want to obtain all parsed elements as Vec<T>. (It's like separated_by, but keeping the separators.) In chumsky 0.9, this looked something like:

a.chain(b.chain(a).repeated().flatten()).collect()

In the new chumsky, however, there is no more chain. After some struggling, I came up with the following equivalent in chumsky 1.0.0-alpha.4:

let head = a.map(|x| Vec::from([x]));
head.foldl(b.then(a).repeated(), |mut acc, (x, y)| {
    acc.push(x);
    acc.push(y);
    acc
})

This is significantly longer, and IMHO, much harder to understand. (My actual example even involves nested foldl Is there some more canonical way to do this?