[swift-evolution] InternalString class for easy String manipulation

Xiaodi Wu xiaodi.wu at gmail.com
Mon Aug 15 12:42:33 CDT 2016

On Sun, Aug 14, 2016 at 5:41 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!

I can sympathize, but this is tricky.

Fundamentally, if it's going to be a learning and teaching issue, then this
"easy" string should be the default. That is to say, if I write `var a =
"Hello, world!"`, then `a` should be inferred to be of type InternalString
or EasyString, whatever you want to call it.

But, we also want Swift to support Unicode by default, and we want that
support to do things The Right Way(TM) by default. In other words, a user
should not have to reach for a special type in order to handle arbitrary
strings correctly, and I should be able to reassign `a = "你好"` and have
things work as expected. So, we also can't have the "easy" string type be
the default...

I can't think of a way to square that circle.

> Sent from my iPad
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