Jeffrey Lee Hellrung, Jr. wrote:
On Mon, Feb 11, 2013 at 1:47 PM, Peter Dimov <lists@pdimov.com> wrote:
read_ptr<T> pr;
if( write_ptr<T> pw = pr.write() ) { pw->mutate(); pr = std::move( pw ); }
... In fact, now that I think of it, .write should be a move, too.
In the case that pr has a use_count of 1, definitely. I thought that's what you had been proposing all along :)
Yes. I meant syntactically, as well, to match the semantics. ...
The advantage here is that (1) in
read_ptr<T> get_value(); write_ptr<T> p = get_value();
you don't need a write() call,
I would expect most of the time you're not going to be immediately modifying a read_ptr rvalue like above.
Well, you have to return _something_ from get_value. It's going to be either read_ptr or write_ptr. It can't be both. You don't know what the caller needs to do. So if you choose read_ptr for some reason, and the caller needs a write_ptr, all is well (and vice versa - they both move into each other).