Compilare: main.cpp: In function 'int evaluate(std::string)': main.cpp:36:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 36 | for (int i=0; i<tokens.length(); i++) | ~^~~~~~~~~~~~~~~~ main.cpp:46:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 46 | while (i<tokens.length() && isdigit(tokens[i])) | ~^~~~~~~~~~~~~~~~