Compilare: user.cpp: In function ‘bool find(std::string, char)’: user.cpp:11:26: 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:24:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<line.size();++i)if(isalpha(line[i]))++car; ^ user.cpp:25:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<line.size();++i) ^