Compilare: user.cpp: In function ‘std::__cxx11::string reversepolishnotation(std::__cxx11::string)’: user.cpp:29:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0;i< exp.size();i++) ~^~~~~~~~~~~~ user.cpp: In function ‘int value(std::__cxx11::string)’: user.cpp:89:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<exp.size();i++) ~^~~~~~~~~~~ user.cpp:86:9: warning: unused variable ‘answer’ [-Wunused-variable] int answer=0; ^~~~~~ user.cpp: In function ‘int val(int, int, char)’: user.cpp:83:1: warning: control reaches end of non-void function [-Wreturn-type] } ^