SE-0357: Regex String Processing Algorithms

[Michael_Ilseman]

@YOCKOW

The return type should be (upperBound: String.Index, output: RegexOutput)? , shouldn't it?

Thanks, opened [SE-0357] Typos and fixes by milseman · Pull Request #1646 · apple/swift-evolution · GitHub

@YOCKOW

One more thing.

There is explanation why Collection is used instead of Sequence and why it's Collection where SubSequence == Substring . But, is there any explanation why not StringProtocol where SubSequence == Substring and StringProtocol where Self: RangeReplaceableCollection ?

This is just a question. I don’t necessarily hope that, though.

StringProtocol is.... not well designed and insufficient for this purpose alone. We'd still need the where as you pointed out. At that point, overly constraining ourselves isn't that useful and we definitely don't want to be pushing anyone to conform to StringProtocol.

Being able to vend a Substring means that you're also creating a proper String for the base property, and doing so as a subsequence means you're not (likely) doing a copy every time. It's conceivable that we'll support some notion of (safely!) shared strings in the future with move semantics and it's conceivable that a type may vend a string-view. At that point, it's just better to use the slice (or string) as the adapter type without having another conformance to StringProtocol.

TL;DR: StringProtocol doesn't get us anything and we want there to be less of it in the future, not more.