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

[dsimcha]

== Quote from Robert Jacques (sandford at jhu.edu)'s article
> On Sat, 25 Apr 2009 09:16:39 -0400, Andrei Alexandrescu
> <SeeWebsiteForEmail at erdani.org> wrote:
> > Stewart Gordon wrote:
> >> Andrei Alexandrescu wrote:
> >>> It looks we can't make it with only T[]. We need a genuine container
> >>> type, and T[new] was suggested.
> >> <snip>
> >>  What do you mean by a "genuine container type"?
> >
> > One with capacity and probably value semantics.
> >
> > Andrei
> First, capacity is only static (i.e. can be included in the array as you
> suggest) for free-list based allocation. Which is _only_ used by malloc
> and mark-sweep GCs. And I'm really hoping Leandro gives us something
> better than mark-sweep.

But in a pointer bumping GC, the right way to do dynamic arrays would be to
allocate some extra space for the array beyond the length requested, to allow it
to be appended to without being reallocated.  In this case, the extra space is
being allocated under the hood by the array functions, not the garbage collector,
but it's still there and you still need a capacity field to track it without
expensive GC queries.