::type

Hi, I am going through proto user guide. I am getting compiling error for the following piece code (it's pretty much copy and pasted from the guide). I used 1.40 and gcc. #include <iostream> #include #include #include #include #include <cmath> #include <vector> namespace proto = boost::proto; template<int I> struct placeholder {}; // Define some placeholders proto::terminal< placeholder< 1 > >::type const _1 = {{}}; proto::terminal< placeholder< 2 > >::type const _2 = {{}}; struct calculator_context : proto::callable_context< calculator_context const > { // Values to replace the placeholders std::vector<double> args; // Define the result type of the calculator. // (This makes the calculator_context "callable".) typedef double result_type; // Handle the placeholders: template<int I> double operator()(proto::tag::terminal, placeholder) const { return this->args[I]; } }; // Define a pow_fun function object template<int Exp> struct pow_fun { typedef double result_type; double operator()(double d) const { return std::pow(d, Exp); } }; // Define a lazy pow() function for the calculator DSEL. // Can be used as: pow< 2 >(_1) template typename proto::function< typename proto::terminal::type , Arg const & pow1(Arg const &arg) { typedef typename proto::function< typename proto::terminal::type , Arg const & >::type result_type; result_type result = {{{}}, arg}; return result; } int main() { calculator_context ctx; ctx.args.push_back(3); std::cout << boost::proto::eval( pow1<2>( _1 ), ctx ); return 0; } The error says: calc2.cpp: In function 'int main()': calc2.cpp:116: error: no matching function for call to 'eval(boost::proto::exprns_::expr >, 0l>, const boost::proto::exprns_::expr >, 0l>&>, 2l>, calculator_context&)' /auto/cigprod/spg/lx86_64/opt/boost_1_40_0/boost/proto/eval.hpp:91: note: candidates are: typename boost::proto::result_of::eval::type boost::proto::eval(Expr&, Context&) [with Expr = boost::proto::exprns_::expr >, 0l>, const boost::proto::exprns_::expr >, 0l>&>, 2l>, Context = calculator_context] /auto/cigprod/spg/lx86_64/opt/boost_1_40_0/boost/proto/eval.hpp:100: note: typename boost::proto::result_of::eval::type boost::proto::eval(Expr&, const Context&) [with Expr = boost::proto::exprns_::expr >, 0l>, const boost::proto::exprns_::expr >, 0l>&>, 2l>, Context = calculator_context] Thanks. -- View this message in context: http://www.nabble.com/boost%3A%3Aproto-user-guide---compile-error-creating-a... Sent from the Boost - Users mailing list archive at Nabble.com.