On 02/11/2011 09:21 PM, Steven Schveighoffer wrote:
On Fri, 11 Feb 2011 14:49:41 -0500, Andrej Mitrovic
<[email protected]> wrote:
On 2/11/11, Steven Schveighoffer <[email protected]> wrote:
struct Node
{
int id;
string myName;
Node *parent; // only needed if you want to go up the tree.
Node *[] children;
}
-Steve
What are the benefits of using struct pointers instead of classes in this case?
Classes are more heavyweight (hidden vtable ptr, monitor) and have less control
over their allocation. For example, I used to use classes to represent tree
nodes in dcollections' RBTree (which later became std.container.RedBlackTree),
but I found structs use up less space and I can create custom allocators for
them which significantly increase performance.
I noticed once another overhead, namely time of method call (certainly due to
runtime lookup of so-called virtual methods). Was significant, about 3x IIRC.
The only real downside is you occasionally have to deal with the pointer aspect
(but most of the time not, since the dot operator auto-dereferences).
Plus, classes are good if you need polymorphism, or want to restrict allocation
of nodes to the heap. You don't need polymorphism for tree node, and the
restriction isn't necessary in all cases. It might be a good idea to make the
"tree root" a class, but the nodes work better as structs.
...as long as nodes are all of the same type. But isn't it a very common case
to have a hierarchy of node types (which /must/ have a common supertype to all
fit into Node* and/or Node*[] slots)?
I started my last app with struct nodes, then switched to class because was to
much mess to maintain (type annotations and such, manual castings all the way
down, somewhat like hand-made tag unions).
denis
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