Compilare: user.cpp: In function ‘bool este(char, std::string)’: user.cpp:13:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.size();i++) ^ user.cpp: In function ‘int main()’: user.cpp:27:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < line.size(); i++) ^