Compilare: user.cpp: In member function ‘char fast_string_concater::operator[](int) const’: user.cpp:11:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] return x < a.size() ? a[x] : x == a.size() ? '#' : b[x - a.size() - 1]; } ^ user.cpp:11:44: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] return x < a.size() ? a[x] : x == a.size() ? '#' : b[x - a.size() - 1]; } ^ user.cpp: In function ‘void find_occurences(const string&, const string&, std::vector<bool>&)’: user.cpp:24:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] occ[j] = (pi[i] == small.size()); } } } ^