Proposal for fixing dchar ranges

[Brad Anderson]

On Monday, 10 March 2014 at 13:35:33 UTC, Steven Schveighoffer 
wrote:
> I proposed this inside the long "major performance problem with 
> std.array.front," I've also proposed it before, a long time ago.
>
> But seems to be getting no attention buried in that thread, not 
> even negative attention :)
>
> An idea to fix the whole problems I see with char[] being 
> treated specially by phobos: introduce an actual string type, 
> with char[] as backing, that is a dchar range, that actually 
> dictates the rules we want. Then, make the compiler use this 
> type for literals.
>
> e.g.:
>
> struct string {
>    immutable(char)[] representation;
>    this(char[] data) { representation = data;}
>    ... // dchar range primitives
> }
>
> Then, a char[] array is simply an array of char[].
>
> points:
>
> 1. No more issues with foreach(c; "cassé"), it iterates via 
> dchar
> 2. No more issues with "cassé"[4], it is a static compiler 
> error.
> 3. No more awkward ASCII manipulation using ubyte[].
> 4. No more phobos schizophrenia saying char[] is not an array.
> 5. No more special casing char[] array templates to fool the 
> compiler.
> 6. Any other special rules we come up with can be dictated by 
> the library, and not ignored by the compiler.
>
> Note, std.algorithm.copy(string1, mutablestring) will still 
> decode/encode, but it's more explicit. It's EXPLICITLY a dchar 
> range. Use std.algorithm.copy(string1.representation, 
> mutablestring.representation) will avoid the issues.
>
> I imagine only code that is currently UTF ignorant will break, 
> and that code is easily 'fixed' by adding the 'representation' 
> qualifier.
>
> -Steve

Generally I think it's a good idea. Going a bit further you could 
also enable Short String Optimization but you'd have to 
encapsulate the backing array.

It seems like this would be an even bigger breaking change than 
Walter's proposal though (right or wrong, slicing strings is very 
common).