template <int n> class vec { double x[n]; public: vec() { for (int i=0; i<n-1; ++i) x[i]=0; } vec(const vec<n>& v) { for (int i=0; i<n; ++i) x[i]=v(i); } vec(const vec<n-1>& v, const double& y) { for (int i=0; i<n-1; ++i) x[i]=v(i); x[n-1]=y; } inline double operator()(const int i) const { return x[i]; } }; template <int n> vec<n + 1>& operator,(const vec<n>& v, const double& y) { return *(new vec<n + 1>(v, y)); } int main() { vec<4> v; vec<5> w; w=(v,3.); }