VLERange: a range in between BidirectionalRange and RandomAccessRange

[Steven Schveighoffer]

On Tue, 11 Jan 2011 11:54:08 -0500, Andrei Alexandrescu  
<SeeWebsiteForEmail at erdani.org> wrote:

> On 1/11/11 5:30 AM, Steven Schveighoffer wrote:
>> While this makes it possible to write algorithms that only accept
>> VLERanges, I don't think it solves the major problem with strings --
>> they are treated as arrays by the compiler.
>
> Except when they're not - foreach with dchar...

This solitary difference is a very thin argument -- foreach(d;  
byDchar(str)) would be just as good without requiring compiler help.

>
>> I'd also rather see an indexing operation return the element type, and
>> have a separate function to get the encoding unit. This makes more sense
>> for generic code IMO.
>
> But that's neither here nor there. That would return the logical element  
> at a physical position. I am very doubtful that much generic code could  
> work without knowing they are in fact dealing with a variable-length  
> encoding.

It depends on the function, and the way the indexing is implemented.

>> I noticed you never commented on my proposed string type...
>>
>> That reminds me, I should update with suggested changes and re-post it.
>
> To be frank, I think it didn't mark a visible improvement. It solved  
> some problems and brought others. There was disagreement over the  
> offered primitives and their semantics.

It is supposed to be simple, and provide the expected interface, without  
causing any undue performance degradation.  That is, I should be able to  
do all the things with a replacement string type that I can with a char  
array today, as efficiently as I can today, except I should have to work  
to get at the code-units.  The huge benefit is that I can say "I'm dealing  
with this as an array" when I know it's safe

The disagreement will never be fully solved, as there is just as much  
disagreement about the current state of affairs ;)  e.g. should foreach  
default to using dchar?

> That being said, it's good you are doing this work. In the best case,  
> you could bring a compelling abstraction to the table. In the worst,  
> you'll become as happy about D's strings as I am :o).

I don't think I'll ever be 'happy' with the way strings sit in phobos  
currently.  I typically deal in ASCII (i.e. code units), and phobos works  
very hard to prevent that.

-Steve