Ruling out arbitrary cost copy construction?

[Dmitry Olshansky]

On 31.10.2010 6:56, Andrei Alexandrescu wrote:
[snip]
> Walter and I discussed the matter again today and we're on the brink 
> of deciding that cheap copy construction is to be assumed. This 
> simplifies the language and the library a great deal, and makes it 
> perfectly good for 95% of the cases. For a minority of types, code 
> would need to go through extra hoops (e.g. COW, refcounting) to be 
> compliant.
>
> I'm looking for more feedback from the larger D community. This is a 
> very important decision that marks one of the largest departures from 
> the C++ style. Taking the wrong turn here could alienate many 
> programmers coming from C++.
>
> So, everybody - this is really the time to speak up or forever be silent.
>
>
> Andrei

The only things I've ever seen in C++ _correctly_ using _costly_ copy 
constructor are containers and some bignums, but then most of the time 
one need  to define swap for it to perform well in the std::sort for 
instance, and that is oftentimes forgotten.
That indicates that containers are better off being reference types, 
which is what they are in D anyway, and bignums I do belive could use 
COW/small number optimization.

I'd go with cheap constructors assumed given that it simplifies matters 
a lot.

-- 
Dmitry Olshansky