// Learn more about F# at http://fsharp.ne
type 'a Tree =
| Empty
| Branch of 'a * 'a Tree * 'a Tree

let breadth_traverse (tree : Tree<'a>) = // обход дерева в ширину (вывод в строку)
 let rec loop (trees : seq<Tree<'a>>) = seq {
    let values =
      trees
      |> Seq.choose (function
        | Empty -> None
        | Branch (value, _, _) -> Some value)

    yield! values

    let subtrees =
      trees
      |> Seq.collect (function
        | Empty -> Seq.empty
        | Branch (value, left, right) -> seq { yield left; yield right })
      |> Seq.toArray

    if subtrees.Length > 0 then
      yield! loop subtrees
  }
 ()
 loop <| seq { yield tree }