anchor.diff:                  | None -> empty
           )
   
  -
  +    let takeWhile (guard : IMod<bool>) (body : evt<'a>) =
  +        evt (fun scope -> new EventReaders.WhileReader<_>(guard, body.GetReader()))
  + 
   module Test =
       
   
  
positive.code:         { values = List.map (fun (t,v) -> t, f v) h.values; finished = h.finished }      
  
  
  
  type IEventReader<'a> =
      inherit IAdaptiveObject
      inherit IDisposable
  
negative.code: 
      let maxValue : Time = DateTime.MaxValue
      let minValue : Time = DateTime.MinValue
  
  type History<'a> = { values : list<Time * 'a>; finished : bool }
  
  