Additional String Processing APIs

[CTMacUser (Daryle Walker)]

@barnard-b

@wtedst

That is, should "ABCD".removePrefix("ABCZ") remove the first three letters or do nothing at all? How does it communicate this decision?

Only a complete match should be acted upon. In general Swift is very explicit, so we should be ok as long as the behavior pattern of the new API fits with hasPrefix / hasSuffix (and there is proper documentation).

A function that removes on partial prefixes can be composed from the whole-prefix version along with a divergence-testing method.

@uliwitness

In particular, a way to iterate over a String and test whether a certain string or sequence from a CharacterSet is present, and to also get their Range in the String would be really helpful. Something like

extension String {
    func extractIf(prefix: String, in range: inout Range) -> (String, Range)?
    func extracLongesttIf(prefixFrom: CharacterSet, in range: inout Range) -> (String, Range)?
}

extractIf could be done with a divergence-testing function too. extractLongestIf could be adapted from self.firstIndex(where: { !prefixFrom.contains($0) }). Neither requires String; they should be added to Collection in general.