[kerneis]

> It can be shorter still, if all you want is insert and read

Despite the name, I'm afraid this is a simple binary tree implementation, not a BTree:

type 'a tree = Empty | Node of('a * 'a tree * 'a tree);;

Obviously the author didn't know what he was doing (the intended scope was very large, AVL, BTrees, etc. but he stopped after committing this single file).