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
