Re: [boost] [Range] initial feedback on return values of algorithms

From: David Abrahams (dave_at_[hidden])
Date: 2006-02-03 13:49:03

Thorsten Ottosen <tottosen_at_[hidden]> writes:

> David Abrahams wrote:
>> Thorsten Ottosen <tottosen_at_[hidden]> 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.

>>> > 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.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com