RangeExtra

[Robert Jacques]

On Thu, 23 Apr 2009 14:37:37 -0400, Andrei Alexandrescu  
<SeeWebsiteForEmail at erdani.org> wrote:
> dsimcha wrote:
>> CapacityArray:  A range that covers a builtin array and gives it a  
>> capacity
>> field.  All operations that don't have to do with appending are  
>> forwarded to
>> the underlying array via alias this (modulo a few compiler bugs),  
>> meaning that
>> a CapacityArray has an identical compile time interface to a builtin  
>> array,
>> and is implicitly convertible to one.
>
> Upon more thinking, I think we'll have to bit the bullet and define  
> Array!T and Slice!T. Then dmd rewrites:
>
> [ a, b, c ] -> .Array!(typeof(a))(a, b, c)
> T[new] -> .Array!(T)
> new T[n] -> .Array!(T)(n)
> T[] -> .Slice!(T)
>
> It seems increasingly clear that slices alone can't quite cut the  
> mustard.
>
> So your CapacityArray will essentially be the basis of Array.

No. The capacity field hack only works with the current free-list based  
mark-sweep GC. In every other type of GC, the capacity is dynamic and can  
not be cached in the array itself. Introducing a language feature that is  
specific to an implementation seems like a bad idea.