[Boost-users] Re: [Foreach]TroubleiteratingoverBoost.MultiIndexcontainers

From: Jonathan Turkanis (technews_at_[hidden])
Date: 2005-03-03 19:07:53

Thorsten Ottosen wrote:
> "Arkadiy Vertleyb" <vertleyb_at_[hidden]> wrote in message

>> I am not really that familiar with this library, but I assume it has
>> to do with containers, correct?  Assume the following usage
>> (pseudocode)
>>
>> Range(std::vector<MyNamespace::SomeTemplate<boost::multi-index<boost::mpl::v
>> ector> > > )
>>
>> Now ADL will use std, boost, MyNamespace, boost::multi_index, and
>> boost::mpl to find Range.  There is absolutely no guarantee that it
>> won't find conflicting functions :-(
>
> I don't get this. Surely one of the functions would be a better match
> than the others and hence called.

I think Arkadiy might mean that the wrong function could be selected; however,
the class author should be able to figure this out.

Would it be possible to indroduce an extra level of indirection so that Range
can be used with a type even if there are preexisting begin/end/.. functions
that do the wrong thing? For instance,

     template<typename T>
     struct begin_impl {
            typename range_iterator<T>::type
            begin( T& c ) { return adl_begin(c); }

            typename range_const_iterator<T>::type
            begin( const T& c )  { return adl_begin(c); }
      };

    template< class T >
    typename range_iterator<T>::type
    begin( T& c )
    {
         return begin_impl<T>::begin(c);
    }

    template< class T >
    typename range_const_iterator<T>::type
    begin( const T& c )
    {
         return begin_impl<T>::begin(c);
    }

Then as a last resort someone could specialize begin_impl. Or is something like
this already possible?

Jonathan