RangeExtra

[Andrei Alexandrescu]

Robert Jacques wrote:
> 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.

1. STL does the same thing so it's likely a more general issue than one 
might think.

2. This is not a language feature. Different implementations can take 
different routes.


Andrei