Re: [Boost-users] challange to MPL gurus

Subject: Re: [Boost-users] challange to MPL gurus
From: Larry Evans (cppljevans_at_[hidden])
Date: 2011-12-12 16:27:23

On 12/12/11 15:01, Larry Evans wrote:
> On 12/12/11 13:41, Robert Ramey wrote:
> [snip]
>> The example below illustrates one of the problems I'm having.
>> The intent is to test the concept.  for next<I>, the concept
>> check is invoked recurrsively until the end of iteration is
>> encountered.  (I'm assuming it's a list in this test).  But the
>> is_end<false_> branch is always invoked
> [snip]
>> template<typename S>
>> struct ForwardSequence {
>>     typedef typename end<S>::type t2;
>>     BOOST_CONCEPT_ASSERT(( ForwardIterator<t2> ));
> 
> Shouldn't this:
> 
>> is_end<false_> branch is always invoked
> 
> be expected since end<S>::type is being passed to ForwardIterator?
> [snip]
OOPS, never mind.  I see you intentionally passed the end<S>::type to
show the very problem you mentioned.  IOW, even though end<S>::type
is passed, the false_ branch is taken instead of the true_ brancch.

Sorry for noise.  However I haved tried to compile the attached:

and, with gcc4.7, I'm getting:

ramey_iter_concept_check.cpp:19:14: error: explicit specialization in
non-namespace scope 'struct boost::mpl::ForwardIterator<I>'
ramey_iter_concept_check.cpp:20:12: error: template parameters not used
in partial specialization: