ocaml binary tree
# type 'a tree =
| Leaf
| Node of 'a tree * 'a * 'a tree;;
type 'a tree = Leaf | Node of 'a tree * 'a * 'a tree
# let t =
Node (Node (Leaf, 1, Leaf), 2, Node (Node (Leaf, 3, Leaf), 4, Leaf));;
val t : int tree =
Node (Node (Leaf, 1, Leaf), 2, Node (Node (Leaf, 3, Leaf), 4, Leaf))