Compilare: main.cpp: In function 'int evaluate(std::string&)': main.cpp:38:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 38 | for (int i = 0; i < s.size(); i++) { | ~~^~~~~~~~~~ main.cpp:59:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 59 | while (i < s.size() && s[i] >= '0' && s[i] <= '9') | ~~^~~~~~~~~~