Compilare: user.cpp: In function ‘bool find(std::string, char)’: user.cpp:10:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<=s.size();i++) ^ user.cpp: In function ‘int main()’: user.cpp:23:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<= line.size();i++) ^