[boost] Re: [range] update on ADL hooks -- new insight

From: Thorsten Ottosen (nesotto_at_[hidden])
Date: 2005-03-31 07:39:28

"David Abrahams" <dave_at_[hidden]> wrote in message 
news:uhditw87f.fsf_at_boost-consulting.com...
| "Thorsten Ottosen" <nesotto_at_[hidden]> writes:

| > range_adl_begin()
| > range_adl_end()
| > range_adl_size()
| >
| > Any comments before I commit?
|
| [I hope we've dropped "adl_" from the name by now ;-) ]

yes.

| A scheme like this one has at least one advantage that we should be
| sure to take advantage of: it allows us to reduce the number of
| overloads required by conforming range classes.

| // Note: this partial specialization is important!
| template <class Sequence>
| struct begin_iterator<Sequence const>
| {
|    typedef typename sequence::traits<
|        Sequence
|    >::begin_const_iterator type;
| };

|  // Note: no overload for Range const&.  This is never
|  // called directly, so it always receives an lvalue.
|  template <class Range>
|  typename begin_iterator<Sequence>::type
|  sequence_begin(Range& s)
|  {
|      return ... // whatever
|  }

This is a good observation. You can already do that as

template< class R >
inline typename range_result_iterator<R>::type range_begin( R& r );
                      ^^^^^^^^^^^^^^^^^^^^^^^^

I don't use partial specialization, but rather eval_if< is_const<R>, 
const_iterator, iterator>::type, but
I guess that not thaht important.

I will update the docs to reflect this easier way to adopt a new type. And I 
will consider
removing half of the actual function implementations.

-Thorsten