anchor.diff:              delay (fun () ->
                   use r = set.GetReader()
                   r.Update(null)
  -                r.Content |> Seq.map f
  +                r.Content |> Seq.map f |> Seq.toList
               )
           else
               let scope = Ag.getContext()
  
positive.code:     /// elements in the given sequence
      /// </summary>
      let ofSeq (s : seq<'a>) =
          ConstantSet(s) :> aset<_>
      
      /// <summary>
      /// creates a set containing all distinct 
  
negative.code:             member x.Copy = x :> aset<_>
  
              member x.GetReader () =
                  let r = new OneShotReader<'a>(content.Value |> Seq.map Add |> Seq.toList)
                  r :> IReader<_>
  
          new(content : Lazy<list<'a>>) = ConstantSet<'a>(lazy (HashSet content.Value))
          new(content : Lazy<seq<'a>>) = ConstantSet<'a>(lazy (HashSet content.Value))
          new(l : list<'a>) = ConstantSet<'a> (lazy (HashSet l))
          new(l : array<'a>) = ConstantSet<'a> (lazy (HashSet l))
          new(l : seq<'a>) = ConstantSet<'a> (lazy (HashSet l))
  
      type private EmptySetImpl<'a> private() =
          static let emptySet = ConstantSet (lazy ([])) :> aset<'a>
          static member Instance = emptySet
  
      let private scoped (f : 'a -> 'b) =
  