David Abrahams wrote:
Thorsten Ottosen <tottosen@dezide.com> writes:
David Abrahams wrote:
Thorsten Ottosen <tottosen@dezide.com> writes:
There is also the issue of O(1) size, for which you have not got support in your concept hierarchy.
Did I forget to mention this? Anyway, size() is now O(1). If you want a generic version, dictance(rng) is supplied instead.
That's not what I mean. Is there a way to distinguish, at compile-time, a range that has support for O(1) size from one that does not? One needs that for important "benefit and beauty"-destroying optimzations that you dislike so.
ok, if range_category<R>::type is convertible to std::random_access_iterator_tag, then you may call boost::size(rng)
There are non-random-access ranges/containers that have O(1) size.
That is true that eg. std::list<T>::size() might be O(1). But how do you detect that? (A: you can't). IIRC, you where one of the people who were very conserned about the performance discontinuity induced by boost::size() is its original form. I now totally agree that such discontinuities are more harmful than useful. Anyway, what issue are you really talking about. I must be missing something.
And then there's property maps.
How do they relate to this?
They're an important part of a generalized range concept.
perhaps, but its hard for me to see how and why they are it. how do you imagine that property maps would affect the interface of range-based algorithms?
isn't range concepts orthogonal to PMs?
No, a more general range concept is a property map and two cursors, rather than just two iterators.
Ok, but it still appears to me that you basically replace iterators with cursors. Boost.range is merely a utility layer on top of a more generic fabric. It shouldn't matter what lies underneith. For example, if I write boost::unique( rng ) I don't care about if it is cursors or iterators doing the hard work. Unlike some, I fully support your and Dietmars efforts to develop the cursor/pm abstraction. But I don't see how it is relevant to boost.range right now. -Thorsten