Compilare: main.cpp: In function 'std::vector<std::vector<int> > prod(std::vector<std::vector<int> >, std::vector<std::vector<int> >)': main.cpp:14:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<a.size();i++) { ~^~~~~~~~~ main.cpp:16:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<b[0].size();j++) { ~^~~~~~~~~~~~ main.cpp:18:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int k=0;k<b.size();k++) rasp[i][j] = s(rasp[i][j], p(a[i][k], b[k][j])); ~^~~~~~~~~