Compilare: main.cpp: In function 'std::vector<int> prod(std::vector<int>, std::vector<int>)': main.cpp:40:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < x.size(); ++i) ~~^~~~~~~~~~ main.cpp:41:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j = 0; j < y.size(); ++j) ~~^~~~~~~~~~ main.cpp:43:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < p.size(); ++i) ~~^~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:80:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < prime.size() && prime[i] <= nr; ++i) ~~^~~~~~~~~~~~~~