1template <int n> class vec {
2    double x[n];
3
4    public:
5    vec() {
6 for (int i=0; i<n-1; ++i) x[i]=0;
7    }
8
9    vec(const vec<n>& v) {
10 for (int i=0; i<n; ++i) x[i]=v(i);
11    }
12
13    vec(const vec<n-1>& v, const double& y) {
14 for (int i=0; i<n-1; ++i) x[i]=v(i);
15 x[n-1]=y;
16    }
17
18    inline double operator()(const int i) const {
19 return x[i];
20    }
21};
22
23
24template <int n> vec<n + 1>& operator,(const vec<n>& v, const double& y) {
25    return *(new vec<n + 1>(v, y));
26}
27
28
29int main() {
30    vec<4> v;
31    vec<5> w;
32    w=(v,3.);
33}
34