Range based Collection mutations

Evolution Pitches
6

I'm with Daryle that it's really weird to have the searchy methods restricted to BidirectionalCollection. They don't make sense on basically-unordered collections, sure, but they totally do make sense on linked lists or sequences-made-from-functions. (Well, most of them.)

I'll note that I had a use case recently where I wanted split to actually preserve the separators in the results. You can do this from the API that's here, but it's, uh, not great:

let splits = bigLongString.split(separatedBy: "### ")
let starts = splits.lazy.map { $0.startIndex }
let splitsWithSuffixesExceptLast = zip(starts, starts.dropFirst()).map {
  bigLongString[$0.0..<$0.1]
}
let splitsWithSuffixes =
  splitsWithSuffixesExceptLast + [bigLongString[starts.last!...]]

Perhaps the right answer here is an enum:

enum IncludingSeparatorsBehavior {
  case omitted
  case asPrefix
  case asSuffix
}

and then the behavior I want is includingSeparators: .asSuffix. (Note that the only empty subsequences when including separators will be at the beginning or end of the result.)

Or perhaps the right answer is something like what I wrote above, which doesn't pull its weight in making the implementation more complex.

1 Like