Compilare: main.cpp: In function 'int eval(std::string)': main.cpp:44:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 44 | for (int i = 0; i<s.size(); i++) { | ~^~~~~~~~~ main.cpp:49:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 49 | while (i < s.size() && s[i] >= '0' && s[i] <= '9') { | ~~^~~~~~~~~~