id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
6977	bug in conversion of mpl iterator category tags	Robert Ramey	Joel Falcou	"MPL documentation indicates that bidirectional_iterator_tag is convertible to random_access_iterator_tag. The following code shows that this is not true.
{{{
#include <boost/mpl/iterator_category.hpp>
#include <boost/mpl/iterator_tags.hpp>

#include <boost/mpl/print.hpp>
#include <boost/mpl/assert.hpp>
#include <boost/type_traits/is_convertible.hpp>

using namespace boost::mpl;

print<
    boost::is_convertible<
        bidirectional_iterator_tag,
        random_access_iterator_tag
    >::type
> x5;

BOOST_MPL_ASSERT((
    boost::is_convertible<
        bidirectional_iterator_tag,
        random_access_iterator_tag
    >
));
}}}

The compile time output from this progam is:

{{{
1>------ Build started: Project: test_interval, Configuration: Debug Win32 ------
1>Compiling...
1>test_multi_precision.cpp
1>c:\boostrelease\boost\mpl\print.hpp(51) : warning C4308: negative integral constant converted to unsigned type
1>        c:\projects\boost projects\mpl\tests\test_multi_precision.cpp(15) : see reference to class template instantiation 'boost::mpl::print<T>' being compiled
1>        with
1>        [
1>            T=boost::integral_constant<bool,false>::type
1>        ]
1>c:\projects\boost projects\mpl\tests\test_multi_precision.cpp(22) : error C2664: 'boost::mpl::assertion_failed' : cannot convert parameter 1 from 'boost::mpl::failed ************boost::is_convertible<From,To>::* ***********' to 'boost::mpl::assert<false>::type'
1>        with
1>        [
1>            From=boost::mpl::bidirectional_iterator_tag,
1>            To=boost::mpl::random_access_iterator_tag
1>        ]
1>        No constructor could take the source type, or constructor overload resolution was ambiguous
1>Build log was saved at ""file://c:\Projects\Boost Projects\mpl\tests\vcide\Debug\BuildLog.htm""
1>test_interval - 1 error(s), 1 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
}}}

Robert Ramey"	Bugs	new	To Be Determined	mpl	Boost 1.49.0	Problem		mpl category convert