Compilare: main.cpp: In function 'std::__cxx11::string read(std::__cxx11::string&, int&)': main.cpp:32:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (p < s.size() && isdigit(s[p])) { ~~^~~~~~~~~~ main.cpp: In function 'std::vector<std::__cxx11::basic_string<char> > infix_to_postfix(std::__cxx11::string)': main.cpp:53:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (; p < s.size(); ) { ~~^~~~~~~~~~ main.cpp: In function 'int evaluate_postfix(std::vector<std::__cxx11::basic_string<char> >)': main.cpp:86:9: warning: unused variable 'ans' [-Wunused-variable] int ans = 0, a, b; ^~~