How to iterate over const(RedBlackTree)?

[monarch_dodra]

On Thursday, 2 January 2014 at 14:59:55 UTC, Adam D. Ruppe wrote:
> On Thursday, 2 January 2014 at 13:30:06 UTC, monarch_dodra 
> wrote:
>> Currently, this is not possible. Or if it was, it would have a
>> *very* high code cost inside RBT.
>
> It is possible in theory; RBT returns a separate Range type 
> with opSlice that is implemented in terms of pointers to node. 
> (This is hidden by an alias RBNode!Elem* Node, which gets in 
> the way, but if those were inout(RBNode)* or const()* it'd 
> work).
>
> We can have mutable pointers to const data, which would work 
> with the range. So opSlice returns a mutable range that points 
> back to const data.
>
>
> But in this case, none of the functions in rbtree use const nor 
> inout, and there's some caching (e.g. _left and _right) that 
> I'm not sure can work with it at all anyway. In a const node, 
> the left and right properties won't work..

Right. Doable, but not trivially so :/

Array might be able to pull it off more easily.

That said, it would only solve the "const container => Range"
issue, but the "const range" problem itself would remain :(