On Friday, 17 October 2014 at 01:09:00 UTC, John McFarlane wrote:
On Friday, 3 January 2014 at 07:22:32 UTC, monarch_dodra wrote:
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 :(
I'm trying to get to grips with D, coming from a C++ background
and const correctness is tough thing to get comfortable with.
I've got a member variable that's RedBlackTree and I'd like to
examine its contents inside an invariants() block. Is this
possible at all right now? Obviously, this would be trivial to
achieve using std::set::const_iterator so is it the language or
the library that poses the difficulty for me? Thanks.
Currently, D containers don't offer "ConstRange opSlice() const"
(which would be the equivalent of const_iterator). This could be
a good solution the the issue.
But to answer your question: Both the language and library that
are making your life difficult. For starters, the D language does
not use const the way C++ does, so this usually confuses the
zealous newcomers that want to be "const correct". The library is
also getting in your way in that it does not provide support for
"const(container/range)" nor "container of const".
