On 12/04/2013 02:09 PM, Michael Woerister wrote:
Is it
possible for the structure to be parametrized on smart pointer?
Not without higher kinded types (which eventually we do want--so the
answer is "not yet").
And then we can define a container type, using the generic reference type:
struct Container<T, TRef, TRefFactory> {
items: ~[TRef],
reference_factory: TRefFactory
}
Clever solution! In the cons list, it needs to be a reference to
Node<T>, not to T. Every persistent container library would have to
expose its node type and take as a parameter an allocator for its
Node<T>. Simplified example:
enum Node<T, TNodeRef> {
Nil,
Cons(T, TNodeRef)
}
type IntList = Rc<Node<int, IntList>>;
But that is an infinite type and, as such, does not compile. Instead using
struct IntList(Rc<Node<int, IntList>>);
works and could implement the necessary traits. Or better,
struct RcList<T>(Rc<Node<T, RcList<T>>>);
Ooh, this is within the realm of maybe being reasonable. A persistent
data structure module could provide RcList and ArcList versions. Is
performance affected by the use of traits for this strategy, or does the
way Rust generics are compiled make that a non-issue? Are there other
reasons this is a terrible idea? :)
-Isaac
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