If T[new] is the container for T[], then what is the container for T[U]?

[Andrei Alexandrescu]

Robert Jacques wrote:
> On Sat, 25 Apr 2009 09:07:52 -0400, Andrei Alexandrescu 
> <SeeWebsiteForEmail at erdani.org> wrote:
>> It looks we can't make it with only T[]. We need a genuine container 
>> type, and T[new] was suggested. It would probably have value semantics.
>>
>> T[U] seems to have the same problem. If T[U] is the range, then how do 
>> you call the container?
>>
>> If we follow through with a no-garbage-collected option for the core 
>> types, then we also need to distinguish between a slice and its 
>> container. The fact that we (almost) got away with T[] being at the 
>> same time the container and the slice was that the garbage collector 
>> would collect all unused slices.
>>
>>
>> Andrei
> 
> No, it's perfectly possible to have T[] be the same type for the 
> container and the slice with reference counting instead of a full GC. 
> All you need to do is store a pointer to the memory block's node. Then 
> it's trivial to 1) get the capacity and 2) increase / decrease the 
> reference count. You could even add an 'allocated length' parameter to 
> the node, so you'd avoid some of the slicing bugs in the current 
> implementation.
> 
> struct T[] {
>     T*     ptr;
>     size_t length;
>     void*  memory_block;
> }

Yes, but that way you take the owner (i.e. the memory block) completely 
out of the picture. It would help to give the owner an identity.

Andrei