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#light
#nowarn "57"

type 'a tree =
    Node of 'a * 'a tree list

let tree_elements max_depth tree =
    let rec aux depth (Node(value, children)) =
        if depth < max_depth then
            seq { yield value
                  for child in children ->>
                      aux (depth + 1) child }
        else
            Seq.empty

    aux 0 tree

do
    let tree = Node(1, [ Node(2, [Node(3, [])])
                       ; Node(4, [Node(5, [])])])
    
    for depth = 1 to 3 do
        Printf.printf "depth = %d\n" depth
        for elem in tree_elements depth tree do
            Printf.printf "%d " elem
        print_newline()
    read_line() |> ignore

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 #light

// tree type
type Tree<'a> =
| Node of Tree<'a> list
| Value of 'a

// creating the tree
let tree =
    Node( [ Node( [Value "one"; Value "two"] ) ;
        Node( [Value "three"; Value "four"] ) ] )


// walking the tree
let rec printTreeValues x =
    match x with
    | Node l -> List.iter printTreeValues l
    | Value x ->
        print_any x
        print_string ", "
        
// apply the tree function
printTreeValues tree