Binary-tree-traversal.fs

// Dummy definition of the binary tree:
type Deque<'a> =
 | Empty
 | Node of Deque<'a> * 'a * Deque<'a>

// Traverse from "front" (L) to "back" (R):
let rec items D =
 match D with
 | Empty       -> Seq.empty
 | Node(L,x,R) -> seq {
                    yield! items(L)
                    yield  x
                    yield! items(R)
                  }

// Test tree; this reflects the insertion of elements 1, 2, 3 (in this order) at the front:
let T = Node( Node(Empty, 3, Empty),
              2,
              Node(Empty, 1, Empty) )
               
// The following would output something like, "val it : seq<int> = seq [3; 2; 1]"
let ts = items T