> From: Beman Dawes [mailto:bdawes@acm.org]
[snip]
> * Because user needs are so varied, Standard Library smart
> pointers should
> support a full feature model, including user supplied behavior. A
> policy-based design is seen as the only candidate likely to meet this
> criteria.
[snip]

It's analogy time:

User needs are varied for containers. Thus, we have list, vector, deque, set, map etceteras to choose from, all with different performance guarantees for different operations. This seems like a very reasonable tradeoff, and although I personally wouldn't mind typing std::container<std::red_black_tree>, many users would. Of course, this would tie the interface to the implementation too hard, so I might end up writing std::container<std::logarithmic_time_insertion, std::logarithmic_time_find...> and so on.

User needs are varied for smart pointers. Thus, we have auto_ptr, scoped_ptr, scoped_array, shared_ptr, shared_array and weak_ptr for different behaviors. This seems like a very reasonable tradeoff, and although I personally wouldn't mind typing (of typedef'ing) boost::smart_resource<boost::reference_counted, boost::resource_allocated_with_operator_new...>, many users would.

Typedef et al add a protective shield from complexity, and that's indeed a strong argument - "you can still use shared_ptr (or equivalent) as with the current interface/implementation in Boost". Sure. At least sometimes. If I do, the policies will have bought me nothing. If I don't, I've gone beyond compatibility (type and binary) with those typedef'ed smart pointers anyway. It's back to roll-your-own, but now with policies rather than the whole ball-of-smart-pointer.

It is (was?) my understanding that Boost.smart_ptr is the most widely used and most recommended smart pointer library around. Books, magazines, experts, Boosters, and users; most are endorsing this library, but still it is being questioned as a suitable addition to the Standard Library?

Oh, by the way, I *really like* the smart_ptr library ;-)

Bjorn "sorry for speaking although I didn't attend" Karlsson