More general list matching

[mbravenboer]

It would be really nice if we could write patterns like this:

[xs..., p(x), ys...]

This would match the first p(x) in the list. It's important here that matching is not greedy. Some ad-hoc support could be implement, but it gets quickly more challenging to cover all cases correctly. I believe we should compile the patterns into an automaton like regular expressions. The design of this would need to be worked out in some more detail.

Some quick thoughts:

• P... would be like P* , and P should match the elements, not the entire list.
• It would be nice to support more regular expression operators, but we'd have to get a bit creative with mapping those Julia syntax? I don't immediately see great use-cases for those.