anchor.diff:      /// Tries to get the next element of an asynchronous sequence
       /// and returns either the value or an exception.
       // TODO : Simplify this to use the built-in Async.Catch method.
  -    let private tryNext (input : AsyncSeq<_>) =
  +    let private tryNext (source : AsyncSeq<_>) =
           async {
           try
  -            let! v = input
  +            let! v = source
               return Choice1Of2 v
           with ex ->
               return Choice2Of2 ex
  
positive.code:     let singleton (value : 'T) : AsyncSeq<'T> =
          asyncSeq.Yield value
  
      /// Yields all elements of the first asynchronous sequence and then 
      /// all elements of the second asynchronous sequence.
      [<CompiledName("Append")>]
      let rec append (aseq1 : AsyncSeq<'T>) (aseq2 : AsyncSeq<'T>) : AsyncSeq<'T> =
          // Preconditions
          checkNonNull "aseq1" aseq1
          checkNonNull "aseq2" aseq2
  
          asyncSeq.Combine (aseq1, aseq2)
  
      /// Creates an asynchronous sequence that iterates over the given input sequence.
      /// For every input element, it calls the the specified function and iterates
      /// over all elements generated by that asynchronous sequence.
      /// This is the 'bind' operation of the computation expression (exposed using
      /// the 'for' keyword in asyncSeq computation).
      [<CompiledName("Collect")>]
      let rec collect mapping (aseq : AsyncSeq<'T>) : AsyncSeq<'U> =
          // Preconditions
          checkNonNull "aseq" aseq
  
          asyncSeq.For (aseq, mapping)
  
      // --------------------------------------------------------------------------
      // Additional combinators (implemented as async/asyncSeq computations)
  
negative.code:             while true do
                  // Receive next message (when observable ends, caller will
                  // cancel the agent, so we need timeout to allow cancleation)
                  let! msg = mbox.TryReceive 200
                  match msg with
                  | None -> ()
                  | Some (Put value) ->
  