On Mon, Aug 31, 2009 at 7:47 PM, Ryan McConnehey wrote:

I have a mpl::map as follows, with a template parameter of a passed in type and a template parameter of "supported_type" that is a class.

using boost::mpl; enum { value = 1 + supported_type::value }; typedef typename insert >::type type_map;

I'm trying to create a function that searches the map for a given type and returns a numeric value if it's found or -1 if it's not found.

template <typename S> int typeValue(void) { return at< type_map, S, int_<-1> >::type::value; }

The documentation says I can specify a default value for "at" that is returned if the given key isn't found. The compiler, though, says that I've provided too many arguments. Have I called "at" incorrectly? Is the documentation incorrect? Is the fault with the compiler (VS 2005)?

Ryan

I've created a work around using the boost::enable_if and boost::disable_if that provides the functionality I need. I would prefer to use the mpl::at with the default argument if I can. If someone could help me I'd appreciate it. template <typename S> typename boost::enable_if< boost::mpl::has_key< type_map, S >, int >::type typeValue(void) { return boost::mpl::at< type_map, S >::type::value; } template <typename S> typename boost::disable_if< boost::mpl::has_key< type_map, S >, int >::type typeValue(void) { return -1; } Ryan