Compilare: main.cpp: In function 'std::pair<int, int> calc()': main.cpp:22:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(idx < s.size()){ ~~~~^~~~~~~~~~ main.cpp:30:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(idx + 1 == s.size() || s[idx + 1] == '=' || s[idx + 1] == '+' || s[idx + 1] == '-') ~~~~~~~~^~~~~~~~~~~