John Maddock wrote:
In fact in C++11 it makes sense to me have:
namespace boost{ namespace mpl{
template <bool b> using bool_ = std::integral_constant<bool, b>;
I have another solution, which appears good enough to go into Core. We could also enhance mpl::bool_ in the same way. Note that the trait knows nothing about bool_, but dispatch still works. #include <boost/config.hpp> #include <boost/core/enable_if.hpp> // template< bool V > struct bool_ { BOOST_STATIC_CONSTANT( bool, value = V ); template< class T > bool_( T const &, typename boost::enable_if_c< T::value == V >::type * = 0 ) { } }; typedef bool_< false > false_; typedef bool_< true > true_; // #include <boost/core/lightweight_test.hpp> template< class T > struct is_pointer { BOOST_STATIC_CONSTANT( bool, value = false ); }; template< class T > struct is_pointer< T* > { BOOST_STATIC_CONSTANT( bool, value = true ); }; int f( true_ ) { return 5; } int f( false_ ) { return 11; } int main() { BOOST_TEST( f( is_pointer< int* >() ) == 5 ); BOOST_TEST( f( is_pointer< int >() ) == 11 ); return boost::report_errors(); }