RedBlackTree thin wrapper initialization

[Edwin van Leeuwen via Digitalmars-d]

On Wednesday, 28 May 2014 at 08:46:30 UTC, Rene Zwanenburg wrote:
>
> The problem is the initialization of A.tree. Short answer, move 
> it to a constructor and it should work.
>
> Now what I think is going on: default values for member fields 
> must be known at compile time. This is why structs can do 
> something like
>
> struct S
> {
>   int i = 5;
> }
>
> while they're not allowed to define a default constructor.
>
> So it appears the tree is instantiated at compile time and 
> stored somewhere, and the reference to that instance is used as 
> the default value for A.tree. I didn't know this was possible 
> to do with reference type members, and perhaps it should be 
> disallowed. This is highly counter intuitive behavior esp. for 
> people coming from Java.

Thank you for the reply. Does this mean I should never initialize 
classes/objects like that or is it more specific to RBT?

I guess structs have the same problem with classes/objects? That 
makes struct that hold objects quite awkward to use, since you 
can't define a default constructor for structs.

struct S
{
     auto tree = new RedBlackTree!string();
}



PS Sorry for not posting this to the learn forum.