Some material for abstracting the tree zipper and an example

gistfile1.fs

//Get the root tree from a zipper
let rec root (Loc (t, p) as l) = 
        match p with 
        | Top(_) -> t
        | _ -> root (go_up l) 

//creates zipper from a tree
let getZipper t = 
    match t with
        | Empty -> Loc(Empty, Top(""))
        | TreeNode(value,_ )-> Loc(t, Top(value))

//this is the function to use, the zippers are abstracted.
let appendToTree t (branch:list<string>) =
    appendToTreeZipper <| getZipper t <| branch
        |> root     


let branch1 = ["a";"b";"c"]
let tree1 = appendToTree Tree.Empty branch1
let branch2 = ["a";"b";"d"]
let tree2 =  appendToTree tree1 branch2
let branch3 = ["a";"f"]
let final = appendToTree tree2 branch3 
//final corresponds to the following tree
//           a
//          /  \
//        b     f
//      /   \
//    c       d