Compilare: user.cpp: In member function ‘char fast_string_concater::operator[](int) const’: user.cpp:12:21: 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:12:44: 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:25:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] occ[j] = (pi[i] == small.size()); } } } ^ user.cpp: In function ‘void do_test(std::ifstream&, std::ofstream&)’: user.cpp:37:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 1; i < str.size(); ++i){ ^ user.cpp:41:88: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int fin_dr = max(st.size(), dr.size())-1, fin_st = st.size()-1; fin_dr < str.size(); ++fin_st, ++fin_dr){ ^