std.container: fork in the road

[via Digitalmars-d]

On Wednesday, 17 June 2015 at 06:08:57 UTC, Andrei Alexandrescu 
wrote:
> Consider e.g. "SList!T.clear()". Right now it's O(1) and only 
> reassigns the root to point to no element, thus leaving all 
> elements to be collected. Moreover, if there are ranges 
> iterating the now cleared list, they'll just continue wandering 
> in the desert as if nothing happened.
>
> What I think SList should do is first switch to a refcounted 
> implementation. Then, clear() should call destroy() for 
> payloads of all nodes, safely invalidate all ranges, and 
> deallocate memory allocated for all nodes.

I think this decision should be left to the end-user. A container 
that supports only RC is just as bad as one that supports only 
GC. Instead, use SList!T or SList!(Unique!T) or 
SList(RefCounted!T) as appropriate.

All internal metadata, on the other hand, should be treated as 
owned by the container. Calling clear() or removing individual 
elements needs to destroy the associated meta data, which in turn 
will correctly call the payload's (e.g. RefCounted!T or Unique!T) 
destructor if it has one.