> On Aug 17, 2016, at 2:34 PM, Kenny Leung via swift-evolution > <swift-evolution@swift.org> wrote: > > >> William Sumner says: >> Can you be more specific about the improvements you’d like to see? Based on >> an earlier message, you want to be able to use subscripting on strings to >> retrieve visual glyphs, but you can do this now via the .characters >> property, which presents a view of the string’s contents as a collection of >> extended grapheme clusters. > > I did not know about .characters. I would say this addresses the glyph > portion of my issues. > > I still have a problem with not being able to index using simple integers to > create subscripts or ranges. I wrote my own “split" function, and found it > extremely frustrating to have to work with .Index types instead of being able > to use integers for subscripts and ranges. Compared to other languages, this > almost obviates the usefulness of subscripts altogether. I understand that > there are performance implications with translating integer subscripts into > actual indexes in the string, but I guess this is a case where even > generating another view on the string doesn’t do enough (internally) to make > it worthwhile. Perhaps if it did… Again, this is very beginner unfriendly. I > guess I will amend my definition of beginner to not only include people new > to programming, but people already experienced in languages besides Swift. > Now that I think about it, NSString is as powerful as Swift.String when ti > comes to Unicode, and it still allows integer based indexing. > > Another issue I have is that a String itself is not subscriptable, but that > you have to get a view of it. I think String should have some default > subscriptability that “does the right thing”, whatever that is decided to be. > > <heart-to-heart on> > Now that we’re getting to the heart of the problem (thanks for the prompting > me to think more deeply about it), Swift may be more frustrating to learn for > experienced programmers coming from C, Objective-C, Java, Ruby, etc. You try > to do the simplest think like index into a string, and then find out you > can’t - you think to yourself, “I’ve been programming in Objective-C for 20 > years. Why can’t I do this? Am I stupid? Is the Swift team purposely trying > to make this hard for me?” > > I’ve been reading swift-evolution for a long time now, and a reason often > given for design decisions is “term of art”. I believe that integer-based > subscriptablilty is a term of art that should be supported. > <heart-to-heart off>
Note that working with individual characters of a NSString can be unsafe because a visual glyph may be represented by multiple characters. NSString provides methods like rangeOfComposedCharacterSequencesForRange: to enable you to align your character retrievals along grapheme cluster boundaries. You may be interested in this article by Mike Ash, which gives a rationale for the String API, including why indexes aren't simple integers: https://www.mikeash.com/pyblog/friday-qa-2015-11-06-why-is-swifts-string-api-so-hard.html In short, these are not simple accesses but potentially expensive operations, and integer subscripting could give users the assumption that they’re accessing arrays with no performance overhead. Preston _______________________________________________ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution
