https://bit.ly/2BTnjF9

tree_ops.re

type tree = Leaf | Node(int, tree, tree);

let rec sum = (item) => {
  switch (item) {
  | Leaf => 0
  | Node(value, left, right) => value + sum(left) + sum(right);
  }
};

let rec height = (root) => {
  switch (root) {
  | Leaf => 0
  | Node(_, left, right) => 1 + (height(left) > height(right) ? height(left) : height(right));
  }
}

let myTree =
  Node(
    1,
    Node(2, Node(4, Leaf, Leaf), Node(6, Leaf, Leaf)),
    Node(3, Node(5, Leaf, Leaf), Node(7, Leaf, Leaf))
  );

let customTree =
  Node(
    8,
    Node(3, Node(1, Leaf, Leaf), Node(6, Node(4, Leaf, Leaf), Node(7, Leaf, Leaf))),
    Node(10, Leaf, Node(14, Node(13, Leaf, Leaf), Leaf))
  );

Js.log(sum(myTree));
Js.log(height(myTree));

Js.log(sum(customTree));
Js.log(height(customTree));