Re: [boost] [Iterator][MultiIndex]iterator-specificpartition_point-relatedfunctions

Subject: Re: [boost] [Iterator][MultiIndex]iterator-specificpartition_point-relatedfunctions
From: David Abrahams (dave_at_[hidden])
Date: 2008-12-29 07:49:09

on Sun Dec 28 2008, Arno Schödl <aschoedl-AT-think-cell.com> wrote:

>> I'm still having trouble
>> understanding how you can implement a specialization for
>> transform_iterator without knowing more than actually possible about the
>> semantics of the transformation function.
>
> Am I missing something?
>
> namespace boost {
>
> template< typename UnaryFunction, typename It, typename UnaryPred >
> transform_iterator<UnaryFunction, It>
> partition_point(
>   transform_iterator<UnaryFunction, It> itBegin,
>   transform_iterator<UnaryFunction, It> itEnd,
>   UnaryPred pred
> ) { 
>   using boost::partition_point;
>   return make_transform_iterator(
>     partition_point(
>       itBegin.base(),
>       itEnd.base(),
>       bind( pred, boost::bind( itBegin.functor(), _1 ) )
>     ),
>     itBegin.functor()
>   );
> }
>
> }; /* namespace */

OK, but for which iterator can we implement an optimized partition_point
that works for arbitrary predicates?  I thought the point of
"specializing" partition_point was to be able to do something smart with
iterators over sorted values (e.g. something like std::set iterators)

>> > Or only have the default implementation in a separate library and implement the
>> > partition_point overloads in Boost.Iterator/Boost.MultiIndexContainer's
>> > iterator-specific header files, such as transform_iterator.hpp?
>
>> I'm getting confused, sorry.
>
> You a) either implement all custom partition_points together in a library, or b) only
> put the infrastructure for such custom partition_points into a library and put the
> iterator-specific custom partition-points close to the respective iterator
> implementations.

b).

-- 
Dave Abrahams
BoostPro Computing
http://www.boostpro.com