from the BLL/bind documentaion on the cvs: struct A { // the return type equals the third argument type: template T3 operator()(const T1& t1, const T2& t2, const T3& t3); template <class Args> class sig { // get the third argument type (4th element) typedef typename boost::tuples::element<3, Args>::type T3; public: typedef typename boost::remove_cv<T3>::type type; } }; To begin with this piece of code has 2 syntax errors. template // should have class before all parameters struct sig { ... } // missing semicolon If a first time user copy/pastes the example, fixes the syntax errors, defines operator() and tries to call the function with: int i = 7; bind( A(), 1, 2, _1) (i); she gets a hard to parse error because operator() wasn't declared const. I see two possible solutions: 1) Add const to the declaration 2) mention the non constness and show how to call the function object using var(func), with a short note on why that is needed.