Dear all, I have a piece of code in which contains: template void FuncStreamCtx::operator () (tag::shift_right, const L& l, const R& r) const { evaluate_helper(l, *this); const typename result_of::value<R>::type f = value(r); } When I compile this under GCC 4.5.1 (MinGW, WinXP, SP3), I get a large spew of warnings. My related piece of code which I guess would be helpful is: double plus1(double i) {return i + 1;} double plus2(double i) {return i + 2;} struct FuncStreamCtx: callable_context { FuncStreamCtx() {} typedef void result_type; void operator () (tag::terminal, double) const; template void operator () (tag::shift_right, const L&, const R&) const; const vector<double>& state() const {return data_;} private: void set_single_value(double) const; mutable vector<double> data_; }; template<typename Expr> const vector<double>& evaluate_helper(const Expr& e, const FuncStreamCtx& ctx) { boost::proto::eval(e, ctx); return ctx.state(); } template<typename Expr> void evaluate(const Expr& e, vector<double>& v) { const FuncStreamCtx ctx; v = evaluate_helper(e, ctx); } template void FuncStreamCtx::operator () (tag::shift_right, const L& l, const R& r) const { evaluate_helper(l, *this); const typename result_of::value<R>::type f = value(r); } int main() { vector<double> v; evaluate(lit(51.6) >> &plus2 >> &plus2 >> &plus1, v); cout << "Result = "; copy(v.begin(), v.end(), ostream_iterator<double>(cout, " ")); return 0; } I have also included the warnings in the P.S. Any idea what the compiler is saying? And, should I do anything about it? TIA, --Hossein P.S. -------------- Build: Debug in ProtoGame3 --------------- Compiling: main.cpp D:\My Documents\My Programmes\Tutorial\Proto\ProtoGame3\main.cpp: In member function 'void FuncStreamCtx::operator()(boost::proto::tag::shift_right, const L&, const R&) const [with L = boost::proto::exprns_::expr&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>, R = boost::proto::exprns_::expr, 0l>]': D:\Sources\Boost\boost_1_42_0/boost/proto/context/callable.hpp:313:21: instantiated from 'boost::proto::context::callable_eval::result_type boost::proto::context::callable_eval::operator()(Expr&, Context&) const [with Expr = const boost::proto::exprns_::expr&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>, Context = const FuncStreamCtx, boost::proto::context::callable_eval::result_type = void]' D:\Sources\Boost\boost_1_42_0/boost/proto/eval.hpp:100:62: instantiated from 'typename boost::proto::result_of::eval::type boost::proto::eval(Expr&, const Context&) [with Expr = const boost::proto::exprns_::expr&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>, Context = FuncStreamCtx, typename boost::proto::result_of::eval::type = void]' D:\My Documents\My Programmes\Tutorial\Proto\ProtoGame3\main.cpp:44:2: instantiated from 'const std::vector<double>& evaluate_helper(const Expr&, const FuncStreamCtx&) [with Expr = boost::proto::exprns_::expr&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>]' D:\My Documents\My Programmes\Tutorial\Proto\ProtoGame3\main.cpp:52:2: instantiated from 'void evaluate(const Expr&, std::vector<double>&) [with Expr = boost::proto::exprns_::expr&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>]' D:\My Documents\My Programmes\Tutorial\Proto\ProtoGame3\main.cpp:80:53: instantiated from here D:\My Documents\My Programmes\Tutorial\Proto\ProtoGame3\main.cpp:74:43: warning: unused variable 'f' D:\My Documents\My Programmes\Tutorial\Proto\ProtoGame3\main.cpp: In member function 'void FuncStreamCtx::operator()(boost::proto::tag::shift_right, const L&, const R&) const [with L = boost::proto::exprns_::expr&, boost::proto::exprns_::expr, 0l> >, 2l>, R = boost::proto::exprns_::expr, 0l>]': D:\Sources\Boost\boost_1_42_0/boost/proto/context/callable.hpp:313:21: instantiated from 'boost::proto::context::callable_eval::result_type boost::proto::context::callable_eval::operator()(Expr&, Context&) const [with Expr = const boost::proto::exprns_::expr&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>, Context = const FuncStreamCtx, boost::proto::context::callable_eval::result_type = void]' D:\Sources\Boost\boost_1_42_0/boost/proto/eval.hpp:100:62: instantiated from 'typename boost::proto::result_of::eval::type boost::proto::eval(Expr&, const Context&) [with Expr = const boost::proto::exprns_::expr&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>, Context = FuncStreamCtx, typename boost::proto::result_of::eval::type = void]' D:\My Documents\My Programmes\Tutorial\Proto\ProtoGame3\main.cpp:44:2: instantiated from 'const std::vector<double>& evaluate_helper(const Expr&, const FuncStreamCtx&) [with Expr = boost::proto::exprns_::expr&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>]' D:\My Documents\My Programmes\Tutorial\Proto\ProtoGame3\main.cpp:73:2: instantiated from 'void FuncStreamCtx::operator()(boost::proto::tag::shift_right, const L&, const R&) const [with L = boost::proto::exprns_::expr&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>, R = boost::proto::exprns_::expr, 0l>]' D:\Sources\Boost\boost_1_42_0/boost/proto/context/callable.hpp:313:21: instantiated from 'boost::proto::context::callable_eval::result_type boost::proto::context::callable_eval::operator()(Expr&, Context&) const [with Expr = const boost::proto::exprns_::expr&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>, Context = const FuncStreamCtx, boost::proto::context::callable_eval::result_type = void]' D:\Sources\Boost\boost_1_42_0/boost/proto/eval.hpp:100:62: instantiated from 'typename boost::proto::result_of::eval::type boost::proto::eval(Expr&, const Context&) [with Expr = const boost::proto::exprns_::expr&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>, Context = FuncStreamCtx, typename boost::proto::result_of::eval::type = void]' D:\My Documents\My Programmes\Tutorial\Proto\ProtoGame3\main.cpp:44:2: instantiated from 'const std::vector<double>& evaluate_helper(const Expr&, const FuncStreamCtx&) [with Expr = boost::proto::exprns_::expr&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>]' D:\My Documents\My Programmes\Tutorial\Proto\ProtoGame3\main.cpp:52:2: instantiated from 'void evaluate(const Expr&, std::vector<double>&) [with Expr = boost::proto::exprns_::expr&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>]' D:\My Documents\My Programmes\Tutorial\Proto\ProtoGame3\main.cpp:80:53: instantiated from here D:\My Documents\My Programmes\Tutorial\Proto\ProtoGame3\main.cpp:74:43: warning: unused variable 'f' D:\My Documents\My Programmes\Tutorial\Proto\ProtoGame3\main.cpp: In member function 'void FuncStreamCtx::operator()(boost::proto::tag::shift_right, const L&, const R&) const [with L = boost::proto::utility::literal, R = boost::proto::exprns_::expr, 0l>]': D:\Sources\Boost\boost_1_42_0/boost/proto/context/callable.hpp:313:21: instantiated from 'boost::proto::context::callable_eval::result_type boost::proto::context::callable_eval::operator()(Expr&, Context&) const [with Expr = const boost::proto::exprns_::expr&, boost::proto::exprns_::expr, 0l> >, 2l>, Context = const FuncStreamCtx, boost::proto::context::callable_eval::result_type = void]' D:\Sources\Boost\boost_1_42_0/boost/proto/eval.hpp:100:62: instantiated from 'typename boost::proto::result_of::eval::type boost::proto::eval(Expr&, const Context&) [with Expr = const boost::proto::exprns_::expr&, boost::proto::exprns_::expr, 0l> >, 2l>, Context = FuncStreamCtx, typename boost::proto::result_of::eval::type = void]' D:\My Documents\My Programmes\Tutorial\Proto\ProtoGame3\main.cpp:44:2: instantiated from 'const std::vector<double>& evaluate_helper(const Expr&, const FuncStreamCtx&) [with Expr = boost::proto::exprns_::expr&, boost::proto::exprns_::expr, 0l> >, 2l>]' D:\My Documents\My Programmes\Tutorial\Proto\ProtoGame3\main.cpp:73:2: instantiated from 'void FuncStreamCtx::operator()(boost::proto::tag::shift_right, const L&, const R&) const [with L = boost::proto::exprns_::expr&, boost::proto::exprns_::expr, 0l> >, 2l>, R = boost::proto::exprns_::expr, 0l>]' D:\Sources\Boost\boost_1_42_0/boost/proto/context/callable.hpp:313:21: instantiated from 'boost::proto::context::callable_eval::result_type boost::proto::context::callable_eval::operator()(Expr&, Context&) const [with Expr = const boost::proto::exprns_::expr&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>, Context = const FuncStreamCtx, boost::proto::context::callable_eval::result_type = void]' D:\Sources\Boost\boost_1_42_0/boost/proto/eval.hpp:100:62: [ skipping 2 instantiation contexts ] D:\My Documents\My Programmes\Tutorial\Proto\ProtoGame3\main.cpp:73:2: instantiated from 'void FuncStreamCtx::operator()(boost::proto::tag::shift_right, const L&, const R&) const [with L = boost::proto::exprns_::expr&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>, R = boost::proto::exprns_::expr, 0l>]' D:\Sources\Boost\boost_1_42_0/boost/proto/context/callable.hpp:313:21: instantiated from 'boost::proto::context::callable_eval::result_type boost::proto::context::callable_eval::operator()(Expr&, Context&) const [with Expr = const boost::proto::exprns_::expr&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>, Context = const FuncStreamCtx, boost::proto::context::callable_eval::result_type = void]' D:\Sources\Boost\boost_1_42_0/boost/proto/eval.hpp:100:62: instantiated from 'typename boost::proto::result_of::eval::type boost::proto::eval(Expr&, const Context&) [with Expr = const boost::proto::exprns_::expr&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>, Context = FuncStreamCtx, typename boost::proto::result_of::eval::type = void]' D:\My Documents\My Programmes\Tutorial\Proto\ProtoGame3\main.cpp:44:2: instantiated from 'const std::vector<double>& evaluate_helper(const Expr&, const FuncStreamCtx&) [with Expr = boost::proto::exprns_::expr&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>]' D:\My Documents\My Programmes\Tutorial\Proto\ProtoGame3\main.cpp:52:2: instantiated from 'void evaluate(const Expr&, std::vector<double>&) [with Expr = boost::proto::exprns_::expr&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>&, boost::proto::exprns_::expr, 0l> >, 2l>]' D:\My Documents\My Programmes\Tutorial\Proto\ProtoGame3\main.cpp:80:53: instantiated from here D:\My Documents\My Programmes\Tutorial\Proto\ProtoGame3\main.cpp:74:43: warning: unused variable 'f' Linking console executable: bin\Debug\ProtoGame3.exe Output size is 1.08 MB Process terminated with status 0 (0 minutes, 4 seconds) 1 errors, 3 warnings