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

[Max Samukha]

On Sat, 25 Apr 2009 08:07:52 -0500, 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

T![] T![U] (kidding)
T[:] T[:U] 

FWIW, Qt uses by-value containers with COW and it looks like they are
ok for many usages. I'd like to see a std.containers module defining
containers with semantics based on a policy:

enum CopyPolicy
{
   Always,  // by value
   OnWrite, // by value with COW
   Never      // by reference
}

Then we could use the most appropriate policy for built-in arrays (I
think it should be by-value with COW).

module object;
import std.containers;

template Array(T)
{
    alias CoolArray!(T, CopyPolicy.OnWrite) Array;
}

and still be able to use containers with different policies when
necessary.