[boost] Re: Proposal for 'is_dereferenceable' and other templatemetafunctions

From: Tobias Schwinger (tschwinger_at_[hidden])
Date: 2004-09-13 16:08:25

Daniel Wallin wrote:
> It's necessary to specialize the trait classes to handle fundamental
> types, for instance:
> 
>   check_add<float, int*>
> 
> Would trigger a compilation error otherwise.
> 

#include <boost/mpl/if.hpp>
#include <boost/type_traits/is_fundamental.hpp>
#include <boost/preprocessor/arithmetic/dec.hpp>

// adding this in namespace boost::result_check_:

template<class T>
struct boxed_fundamental
{
   operator T ();
};

template <class T>
struct make_arg
{
   typedef typename add_reference<
                  typename mpl::if_< is_fundamental<T>
                                   , boxed_fundamental<T>
                                   , T
                                   >::type
                                 >::type type;
};

// changing the RESULT_CHECK_LOCAL_ARG macro to this:

#define BOOST_RESULT_CHECK_LOCAL_ARG(z, n, text) \
     static typename make_arg<T##n>::type \
         BOOST_PP_CAT(_, BOOST_PP_INC(n));

// finally, weakening fallback overload within the
// BOOST_RESULT_CHECK macro

no_overload_tag function( \
   BOOST_PP_ENUM_PARAMS(BOOST_PP_DEC(arity) \
                       , any BOOST_PP_INTERCEPT), ...);  \

// ...should work