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

Subject: Re: [boost] [multi_array] Bug in rbegin(), rend()?
From: John Reid (j.reid_at_[hidden])
Date: 2009-05-21 05:58:42

Tushar Chowdhury wrote:
> Agreed John. Getting the same error here.
> 
> I believe it is a bug in the class <iterator_facade>

As far as I can tell multi_array seems to use the iterator facade to 
define its iterator and uses boost::reverse_iterator to define its 
reverse iterator. I'm not sure if the problem is in multi_array, 
iterator_facade or reverse_iterator.

John.

> On 5/19/09, John Reid <j.reid_at_[hidden]> wrote:
>> 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>*)’
>>
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