Under fusion namespace we can write vector<int, double, string> v(1, 2.4, "hello"); print_type( at_c<2>(v) ); // prints string print_value( at_c<2>(v) ); // prints "hello" But number 2 in our example must be a compile time constant, we cannot write int idx = 2; at_c<idx>(v); // compile error here Sometime accessing an element in a fusion sequence indexed by a runtime variable could be useful, something like the following: vector<int, double, string> v(1, 2.4, "hello"); int idx; cout << "Give me an index" << endl; cin >> idx; apply_at(v, idx, print_type); // prints string if idx == 2, or int if idx == 0 apply_at(v, idx, print_value); // prints "hello" if idx == 2, or 1 if idx == 0 Because I didn't find something similar in fusion and I needed that for code I'm writing I cooked up my solution, it's very easy and if someone is interested I can post it. Marco P.S: If someone could point me to an already available solution it would be appreciated ;-) I just missed it.