[boost] [multi_array] Bug in rbegin(), rend()?

Subject: [boost] [multi_array] Bug in rbegin(), rend()?
From: John Reid (j.reid_at_[hidden])
Date: 2009-05-19 10:27:09

I'm having some trouble iterating over a 2-dimensional multi_array in 
reverse order. I'm using boost 1.38 with gcc-4.2.4 and the following 
code won't compile with the error given below:

#include <boost/multi_array.hpp>

template< typename It >
void
iterate_over( It begin, It end )
{
        while( end != begin ) {
                begin->end() - begin->begin();
                ++begin;
        }
}

void
test()
{
        boost::multi_array< double, 2 > m;
        iterate_over( m.begin(), m.end() );   // works fine
        iterate_over( m.rbegin(), m.rend() ); // causes error
}

This looks to me like a bug in the implementation of the reverse 
iterator for multi_array. Am I wrong?

John.

/home/john/Dev/ThirdParty/boost/boost_1_38_0/boost/iterator/iterator_facade.hpp: 
In static member function ‘static typename 
boost::mpl::if_<boost::is_reference<Reference>, Pointer, 
boost::detail::operator_arrow_proxy<ValueType> >::type 
boost::detail::operator_arrow_result<ValueType, Reference, 
Pointer>::make(Reference) [with ValueType = boost::multi_array<double, 
1ul, std::allocator<double> >, Reference = 
boost::detail::multi_array::sub_array<double, 1ul>, Pointer = 
boost::multi_array<double, 1ul, std::allocator<double> >*]’:
/home/john/Dev/ThirdParty/boost/boost_1_38_0/boost/iterator/iterator_facade.hpp:648: 
   instantiated from ‘typename 
boost::detail::operator_arrow_result<typename 
boost::detail::iterator_facade_types<Value, CategoryOrTraversal, 
Reference, Difference>::value_type, Reference, typename 
boost::detail::iterator_facade_types<Value, CategoryOrTraversal, 
Reference, Difference>::pointer>::type boost::iterator_facade<I, V, TC, 
R, D>::operator->() const [with Derived = 
boost::reverse_iterator<boost::detail::multi_array::array_iterator<double, 
double*, mpl_::size_t<2ul>, 
boost::detail::multi_array::sub_array<double, 1ul> > >, Value = 
boost::multi_array<double, 1ul, std::allocator<double> >, 
CategoryOrTraversal = 
boost::detail::iterator_category_with_traversal<std::input_iterator_tag, 
boost::random_access_traversal_tag>, Reference = 
boost::detail::multi_array::sub_array<double, 1ul>, Difference = long int]’
src/sandbox/seqan_sandbox.cpp:12:   instantiated from ‘void 
iterate_over(It, It) [with It = 
boost::reverse_iterator<boost::detail::multi_array::array_iterator<double, 
double*, mpl_::size_t<2ul>, 
boost::detail::multi_array::sub_array<double, 1ul> > >]’
src/sandbox/seqan_sandbox.cpp:22:   instantiated from here
/home/john/Dev/ThirdParty/boost/boost_1_38_0/boost/iterator/iterator_facade.hpp:326: 
error: no matching function for call to 
‘implicit_cast(boost::detail::multi_array::sub_array<double, 1ul>*)’