Compilare: main.cpp: In function 'int eval(std::__cxx11::string)': main.cpp:28:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.size(); i++) ~~^~~~~~~~~~ main.cpp:36:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (i < s.size() && isdigit(s[i])) { ~~^~~~~~~~~~ main.cpp: In function 'int Operatie(int, int, char)': main.cpp:22:1: warning: control reaches end of non-void function [-Wreturn-type] } ^