anchor.diff:      
   /////////////////////////////////////////////////////////////////////////
   
  -module Async =
  +module AsyncMb =
     type Stream<'a> = MailboxProcessor<AsyncReplyChannel<'a>>
     let inline take (s: Stream<'a>) = s.PostAndAsyncReply (fun x -> x)
   
  
positive.code:    for n in ns do
       HopacCh.run n |> cleanup
     for n in ns do
       HopacPromise.run n |> cleanup
     for n in ns do
       Async.run n |> cleanup
  
negative.code:       next
  
    let sieve : Job<Stream<_>> =
      let rec sieve nats =
        let prime = nats.Value
        {Value = prime;
         Next =
          Promise.Now.delay (nats.Next >>= filter (fun x -> x % prime <> 0) |>> sieve)}
      iterate (fun x -> x+1) 2 |>> sieve
  
    let primes n = Job.delay <| fun () ->
      let before = GC.GetTotalMemory true
  