Thorsten Ottosen wrote:

MB wrote:

...

Hi,

I think non-intrusive customization way needs four specializations; 'X', 'const X', 'volatile X' and 'const volatile X'. At last, twenty specializations are required for five metafunctions. I view that's something like the pitfall of public virtual interfaces.

if that is true, then it is certainly bad.

...

Only range_result_iterator happens to work around by using remove_cv.

See:

I added followings to <libs/range/doc/example.cpp>:

template< class Range > typename boost::range_result_iterator<Range>::type my_begin(Range& rng) { return boost::begin(rng); }

// then... my_begin(cpair); // error

right, because we instantiate range_const_iterator< const T >, which should never happen.

...

Why not something like:

template< class T > struct range_result_iterator : mpl::eval_if< is_const<T>, range_const_iterator< typename remove_cv<T>::type >, range_iterator< typename remove_cv<T>::type > > { };

Seems right to me.

I the latest release I actually added similar stuff to begin(),end() to remove const qualifiers from "const T", since it lead to such "const T" being used to instatiate metafunctions *even though* the overload was never picked.

So this means that begin()/end() must also remove volatile. Cute :-)

Thanks for the feedback

-Thorsten

I show my current private patch: namespace boost { namespace range_detail { template< class T > struct remove_cv_ : #if !BOOST_WORKAROUND(BOOST_MSVC, == 1310) remove_cv<T> #else mpl::eval_if< is_array<T>, // is_const is broken if array remove_volatile<T>, remove_cv<T> > #endif { }; } // namespace range_detail ////////////////////////////////////////////////////////////////////////// // default ////////////////////////////////////////////////////////////////////////// template< class T > struct range_result_iterator : mpl::eval_if< is_const<T>, range_const_iterator< typename range_detail::remove_cv_<T>::type >, range_iterator< typename range_detail::remove_cv_<T>::type > > { }; } // namespace boost But I guess this is not portable for broken compilers, though eVC4, VC7.1, VC8 and GCC3.4 seem to work. All I can say is "Be careful about 'boost::is_const'." :-) Regards, MB p-stade.sourceforge.net