Compilare: user.cpp: In function ‘void write()’: user.cpp:15:45: warning: capture of variable ‘os’ with non-automatic storage duration [enabled by default] std::for_each(a.begin(), a.end(), [&os](const int& nr) { os << nr + 1 << " ";}); ^ user.cpp:6:10: note: ‘std::ofstream os’ declared here ofstream os("damesah.out"); ^ user.cpp: In function ‘int main()’: user.cpp:87:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (unsigned int i = 0; i <= n; ++i) ^