Search Using Continuations

Here's my first pass at a search using continuations. This is my first non-trivial implementation of continuations! It may not be the simplest way to do this, and it still returns a list in the opposite order from that which I want, but it's a start. I even made it generic. (Note: this version is only for acyclic graphs; this will be fixed in the next version.)

As always, presented without warranty or implied fitness. That and there may still be a bug or two.

p.s. The name "SeqTryPick" is an anachronism from experiments involving Seq; it will be changed in the next version.

open System
open System.Collections.Generic


[<System.Diagnostics.DebuggerDisplayAttribute("{S}")>]
type Bob (s:string) =
  
  let h = new HashSet<Bob>()
  
  member this.Add b =
    h.Add(b) |> ignore
    this
  
  member this.H = h
  member this.S = s 
  

let rec internal SeqTryPick0<'a,'b> (fe:'a->IEnumerator<'a>)
                                    (ft:'a->bool)
                                    (e:IEnumerator<'a>)
                                    (ff:unit->'a list) 
                                    (fs:'a list->'a list) =
  match e.MoveNext() with
  | false -> ff()
  | _ -> 
      let c = e.Current
      match ft c with
      | true -> c::fs([])
      | false -> 
          (SeqTryPick0 
            fe
            ft
            e 
            (fun ()->
               SeqTryPick0 
                 fe
                 ft
                 (fe c) 
                 ff 
                 (fun s->c::fs(s)))
             fs)
             
and SeqTryPick<'a,'b> (fe:'a->IEnumerator<'a>)
                      (ft:'a->bool)
                      (a:'a) =
  match ft a with 
  | true -> [a]
  | false ->
      SeqTryPick0 
        fe
        ft
        (fe a) 
        (fun ()->[]) 
        (fun a0->a::a0)  

let b =
  (Bob "b").Add(
    (Bob "b0").Add(
      (Bob "b00").Add((Bob "b000")).Add((Bob "b001"))).Add(
      (Bob "b01").Add((Bob "b010")).Add((Bob "b011")))).Add(
    (Bob "b1").Add(
      (Bob "b10").Add((Bob "b100")).Add((Bob "b101").Add((Bob "b1010")).Add((Bob "b1011")))).Add(
      (Bob "b11").Add((Bob "b110")).Add((Bob "b111")))) 
    
let x = 
  SeqTryPick 
    (fun (b:Bob)->(b.H.GetEnumerator():>IEnumerator<Bob>)) 
    (fun (b:Bob)->b.S="b1011")
    b

Console.ReadLine() |> ignore