/in/calc.cpp:134:13: error: unknown type name 'string'; did you mean 'std::string'?
void insert(string input, Dlist<int> *stack){
            ^~~~~~
            std::string
/usr/bin/../lib/gcc/x86_64-linux-gnu/7.5.0/../../../../include/c++/7.5.0/bits/stringfwd.h:74:33: note: 'std::string' declared here
  typedef basic_string<char>    string;   
                                ^
1 error generated.
/in/Compile/Makefile:44: recipe for target 'buildCalc' failed
make: *** [buildCalc] Error 1