Ruling out arbitrary cost copy construction?

[Andrei Alexandrescu]

On 10/30/10 2:24 CDT, Don wrote:
> Andrei Alexandrescu wrote:
>>> If anything, I'm inclined to say that we assume that the postblit is
>>> O(1) and
>>> let the programmer worry about any inefficiencies. We can point out
>>> that anything
>>> worse that O(1) will be a performance problem, but it seems to me
>>> that any
>>> attempt to either accomodate arbitrary cost postblit constructors or
>>> to try and
>>> use any kind of scheme which forces programmers to write postblits in
>>> a certain
>>> way is too complicated and doomed to failure. And even if it works,
>>> it will be
>>> highly annoying to deal with.
>>
>> It sure is annoying, but it does work.
>>
>> Don, can you estimate how difficult it would be to convert BigInt to a
>> refcounted implementation?
>
> At the moment, I think it's impossible.
> Has anyone succesfully implemented refcounting in D? As long as bug 3516
> (Destructor not called on temporaries) remains open, it doesn't seem to
> be possible.
> Is that the only blocker, or are there others?

I managed to define and use RefCounted in Phobos. File also uses 
hand-made reference counting. I think RefCounted is a pretty good 
abstraction (unless it hits the bug you mentioned.)

Andrei