Compilare: user.cpp: In function ‘void fft(std::vector<Complex>&, int)’: user.cpp:42:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < pol.size(); ++i) ^ user.cpp:51:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < pol.size() / 2; ++i) { ^ user.cpp:61:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < pol.size(); ++i) ^ user.cpp: In function ‘void test()’: user.cpp:81:44: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (ps = 1; ps <= fa.size() + fb.size(); ps<<= 1); ^ user.cpp:86:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < fa.size(); ++i) pol_a[i] = fa[i]; ^ user.cpp:87:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < fb.size(); ++i) pol_b[i] = fb[i]; ^ user.cpp:92:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < pol_a.size(); ++i) ^