[Boost-users] [Bind] How to create a functor which returns one of its arguments?

Hello, All! Is there a simple way to create a functor that returns one of its arguments _1, _2, ...? Does standard unary functor exist, which simply returns its argument unchanged? I.e.: template<typename T> struct arg: public std::unary_function { T operator()(const T &x) const { return x; } }; Then I could write: boost::bind(arg<int>(), _2) to create a functor which returns the value of its second argument, or boost::bind(arg<bool>(), true) to create a functor which always returns true. -- Best regards, Vadim Guchenko [yhw at relost dot net].