/in/calc.cpp:40:32: error: use of undeclared identifier 'to_string'
                T *fo3 = new T(to_string(stoi(*fo1) + stoi(*fo2)));
                               ^
/in/calc.cpp:182:9: note: in instantiation of function template specialization 'arithm<std::__cxx11::basic_string<char> >' requested here
        arithm(dlist, is);
        ^
/in/calc.cpp:232:13: note: in instantiation of function template specialization 'calc<std::__cxx11::basic_string<char> >' requested here
            calc(dlistp, is);
            ^
1 error generated.
/in/Compile/Makefile:44: recipe for target 'buildCalc' failed
make: *** [buildCalc] Error 1