I want to take a boost::bind functor and get the type of its arguments. I can't find any sort of introspection api documented. I tried using mpl but what I came up with doesn't seem to work. Is there a way to do this? A distilled version of my failed attempt follows #include <boost/bind.hpp> #include <boost/mpl/find.hpp> #include <boost/type_traits/function_traits.hpp> template< typename Function, int N > struct arg_n; template< typename Function > struct arg_n< Function, 1 > { typedef typename boost::function_traits< Function >::arg1_type type; }; template< typename Callback, int ArgN > struct arg_type; template< typename Return, typename Signature, typename Args, int ArgN > struct arg_type< boost::_bi::bind_t<Return,Signature,Args>, ArgN > { typedef typename boost::mpl::find< Args, boost::arg<ArgN> >::type iter; // +1 for 0 based find vs 1 based arguments typedef typename arg_n<Signature,iter::pos::value + 1>::type type; }; void foo( int a ) {} template< typename Callback > void bar( Callback cb ) { // trivial usage typedef typename arg_type< Callback, 1 >::type ArgType; cb( ArgType() ); } int main() { bar( boost::bind(&foo,_1) ); } Thanks, -- Michael Marcin