Does D have "structural sharing" of immutable collections?

[Roman D. Boiko]

On Thursday, 24 May 2012 at 01:00:52 UTC, Jonathan M Davis wrote:
> As part of my thesis work, I wrote a program which was counting 
> possible
> tokens in code (as part of an AI attempting to learn about a 
> programming
> language), which required a map of tokens to the number of 
> times that they'd
> been seen. Because I had previously been doing stuff in Haskell 
> for my thesis,
> I continued to use Haskell for that portion, and it was a 
> _huge_ mistake,
> because the performance was _terrible_ - as in it could only 
> process a few
> files in a day kind of terrible. I ultimately had to switch 
> over to another
> language to get it to work (it ended up being Java, but I could 
> have used a
> variety of other languages).
>
> Maybe if I had simply been adding elements to the map, it 
> wouldn't have been
> anywhere near as bad, but since I had to mutate them (and both 
> the map and its
> elments were technically immutable), that become _insanely_ 
> expensive.
>
> So, it's quite possible that you have a use case where using 
> immutable
> containers works really well and isn't a problem, but in what 
> I've dealt with
> personally, I've found it to be a huge performance problem and 
> so am very
> leery of immutable containers.
>
> - Jonathan M Davis

Is source code available?