(* Prints a binary tree sideways *)

type 'a tree =
    | Node of 'a tree * 'a * 'a tree
    | Nil

let rec print t =
    let rec loop n = function
        | Nil -> ()
        | Node(l, x, r) ->
            let spaces = new System.String(' ', n * 4)
            loop (n + 1) r
            printfn "%s%A" spaces x
            loop (n + 1) l
    loop 0 t