Daniel Frey-3 wrote:
On 26.01.2010, at 23:36, Kenny Riddile wrote:
I'm trying to create a type trait to detect the presence of a constructor with a very specific signature.
You might want to have a look into is_constructible. It's a new type trait from the upcoming standard <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2009/n3000.pdf>, and a partial implementation is possible. Here's a version for GCC 4.4+ (requires -std=c++0x):
#include <type_traits>
namespace boost { namespace is_constructible_impl { template< typename T > typename std::add_rvalue_reference< T >::type declval();
template< typename T > decltype( T(), std::true_type() ) select( int );
template< typename T, typename A > decltype( static_cast< T >( declval< A >() ), std::true_type() ) select( int );
template< typename T, typename A1, typename A2 > decltype( T( declval< A1 >(), declval< A2 >() ), std::true_type() ) select( int );
template< typename T, typename A1, typename A2, typename A3 > decltype( T( declval< A1 >(), declval< A2 >(), declval< A3 >() ), std::true_type() ) select( int );
template< typename T, typename A1, typename A2, typename A3, typename A4 > decltype( T( declval< A1 >(), declval< A2 >(), declval< A3 >(), declval< A4 >() ), std::true_type() ) select( int );
// A variadic version of the above is not possible, // GCC 4.4 crashes with an internal compiler error. // GCC 4.5 will likely provide is_constructible itself
template< typename, typename... > std::false_type select( ... ); }
template< typename T, typename... As > struct is_constructible : std::is_same< decltype( is_constructible_impl::select< T, As... >( 0 ) ), std::true_type > { }; }
HTH.
Regards, Daniel
Hi, glad to hear that a partial solution exists. Can this be emulated with Boost.Typeof on C++98 compilers? Best, Vicente -- View this message in context: http://old.nabble.com/detecting-a-constructor-with-a-specific-signature-tp27... Sent from the Boost - Dev mailing list archive at Nabble.com.