Compilare: main.cpp: In function 'std::ostream& operator<<(std::ostream&, per&)': main.cpp:16:1: warning: no return statement in function returning non-void [-Wreturn-type] } ^ main.cpp: In function 'int main()': main.cpp:32:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<v.size(); i++) { ~^~~~~~~~~