Copy constructors for lazy initialization

[Bruno Medeiros]

On 29/05/2010 03:02, Jonathan M Davis wrote:
> Andrei Alexandrescu wrote:
>
> Not knowing what other implications there are, I'm fine with the change, but
> the fact that D creates the array when you try and insert into it (or append
> to it in the case of normal arrays IIRC) rather than blowing up on null
> seems like a source of subtle bugs and that perhaps it's not the best design
> choice. But maybe there was a good reason for that that I'm not aware of, so
> it could be that it really should stay as-is. It's just that it seems
> danger-prone and that the situation that you're trying to fix wouldn't be an
> issue if the array stayed null until the programmer made it otherwise.
>
> - Jonathan M Davis

Yeah, I agree. I mean, for me the problem here is that the 
map/associative-array is not really a value type, nor a reference type, 
but something in between. I think it might be better for it to be just a 
proper reference type.

I'm not saying that Andrei suggestion has no merit though. Rather, I 
have to admit I am not familiar with these C++ idioms and techniques. 
Can someone explain me why we need a copy constructor in the first 
place, instead of just using a reference object, aka a class, and an 
optional clone method?



-- 
Bruno Medeiros - Software Engineer