How to eliminate RTTI in sample code

Question

I'm writing a kd tree, which I think is good enough at this point. I've put the whole template at http://private.org.il/Code%20Projects/kd%20tree%20w%20bb%20cache.zipx

One thing I'd like to do is eliminate RTTI, and specifically calls to dynamic_pointer_cast.

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The relevant part is that I use three classes: an abstract node class, that requires it's derived classes to implement the isInternal() function.

There are two classes that derive from it - an internal node class (function returns true), and a leaf node class (function returns false). Therefore, once isInternal is called, I know to which of the two derived classes the pointer can be casted to.

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The one routine I'm having problem eliminating the call is ApproxNearestNeighborNode, which provides an initial guess for the nearest neighbor search. Currently it looks like this

shared_ptr<kd_leaf_node> ApproxNearestNeighborNode(const kd_point &srcPoint) const
{
    unsigned int Depth = 0;
    shared_ptr<kd_node> Node(m_Root);

    while (Node->isInternal())
    {
        shared_ptr<kd_internal_node> iNode = dynamic_pointer_cast<kd_internal_node>(Node);

        if (srcPoint[Depth++%K] <= iNode->splitVal() || iNode->Right() == nullptr)
            Node = iNode->Left();
        else
            Node = iNode->Right();
    }

    shared_ptr<kd_leaf_node> lNode = dynamic_pointer_cast<kd_leaf_node>(Node);

    return lNode;
}

The two issues that baffle me is keeping the routine iterative, rather than recursive, and returning a smart pointer to the leaf node.

[OK, I think there's a way to do it using shared_from_this, I just hope there's a way to do it rewriting as little code as possible.]

Any other feedback would be appreciated, but off topic, so please send it by email.

Answer 1

As noted by πάντα ῥεῖ, you can replace dynamic_pointer_cast by static_pointer_cast . It seems that your Node->isInternal() check is meant to ensure the dynamic case always succeeds, so a simple search-and-replace is enough.