anchor.diff:          let indexnext = 
             if ar1.[inext] < ar2.[jnext] then (true, inext, jlast)
             else (false, ilast, jnext)
  -        yield Some (indexnext)
  +        yield Some(indexnext)
           yield! index indexnext
         | false, true -> 
           let indexnext = (false, ilast, jnext)
  -        yield Some (indexnext)
  +        yield Some(indexnext)
           yield! index indexnext
         | true, false -> 
           let indexnext = (true, inext, jlast)
  -        yield Some (indexnext)
  +        yield Some(indexnext)
           yield! index indexnext
         | false, false -> yield None }
     let mergeindex = index (false, -1, -1)
  
positive.code:    |> shuffle
     |> List.toArray)
  
  let test4 = mergesort testval
negative.code: open System.Windows
  
  let shuffle (l : 'a array) = 
    let ileft = LinkedList<int>(seq { 0..(l.Length - 1) })
    let rec pick (ar : 'a array) r = 
      match ileft.Count with
      | 0 -> r
  