[Boost-users] Problem with type traits

From: Robert Dailey (rcdailey_at_[hidden])
Date: 2008-07-20 23:22:50

Hi,

I'm trying to create my own struct that is compatible with boost::mpl::or_
as well as boost::enable_if.

I find that using boost::mpl::or_ requires that my structure have a 'type'
member, and enable_if looks for 'value'. Must I define both? What is the
proper way to handle this? Below is my structure:

template< typename t_type >
struct is_sink
{
    typedef typename boost::mpl::or_<
        vfx::io::is_device<t_type>,
        boost::is_same<t_type, vfx::io::Sink>
    > type;
};

The above structure works perfectly fine with boost::mpl::or_, but does not
work for boost::enable_if because it is looking for a 'value' member. I feel
what it should be looking for is is_sink::type::value. An example of how I
use the above structure is below:

template< typename t_source, typename t_data >
typename boost::enable_if<
    boost::mpl::and_<*is_source<t_source>*, boost::is_pod<t_data> >,
    t_source
>::type& operator>> ( t_source& source, t_data& data )
{
    source.Read( reinterpret_cast<boost::uint8_t*>( &data ), sizeof( t_data
) );
    return source;
}