Index lens.

a ::: x ::: c ::: VNil >>> view (L._Pull % ix (FS FZ)) (a L.::: b L.::: c L.::: L.VNil) b

>>> set (L._Pull % ix (FS FZ)) 'x' ('a' L.::: 'b' L.::: 'c' L.::: L.VNil)
'a' ::: 'x' ::: 'c' ::: VNil

Match on non-empty Vec.

Note: lens _Cons is a Prism. In fact, Vec n a cannot have an instance of Cons as types don't match.

Head lens. Note: lens _head is a Traversal'.

>>> view (L._Pull % _head) ('a' L.::: 'b' L.::: 'c' L.::: L.VNil)
'a'

>>> set (L._Pull % _head) 'x' ('a' L.::: 'b' L.::: 'c' L.::: L.VNil)
'x' ::: 'b' ::: 'c' ::: VNil

Tail lens.

Prism from list.