[swift-evolution] InternalString class for easy String manipulation

[William Sumner]

> On Aug 14, 2016, at 4:41 PM, Michael Savich via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Back in Swift 1.0, subscripting a String was easy, you could just use subscripting in a very Python like way. But now, things are a bit more complicated. I recognize why we need syntax like str.startIndex.advancedBy(x) but it has its downsides. Namely, it makes things hard on beginners. If one of Swift's goals is to make it a great first language, this syntax fights that. Imagine having to explain Unicode and character size to an 8 year old. This is doubly problematic because String manipulation is one of the first things new coders might want to do. 
> 
> What about having an InternalString subclass that only supports one encoding, allowing it to be subscripted with Ints? The idea is that an InternalString is for Strings that are more or less hard coded into the app. Dictionary keys, enum raw values, that kind of stuff. This also has the added benefit of forcing the programmer to think about what the String is being used for. Is it user facing? Or is it just for internal use? And of course, it makes code dealing with String manipulation much more concise and readable.
> 
> It follows that something like this would need to be entered as a literal to make it as easy as using String. One way would be to make all String literals InternalStrings, but that sounds far too drastic. Maybe appending an exclamation point like "this"! Or even just wrapping the whole thing in exclamation marks like !"this"! Of course, we could go old school and write it like @"this" …That last one is a joke.
> 
> I'll be the first to admit I'm way in over my head here, so I'm very open to suggestions and criticism. Thanks!

If desired for educational purposes, subscripting can be added to String as an extension. On the other hand, the current APIs convey the performance costs of traversing strings. In my opinion, that is the correct approach to learn in a Unicode-aware world.

Preston
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