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

[Robert Jacques]

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;
}