anchor.diff:              false
         else false
   
  -    // manual state machine instead of a task computation expression, this is visibly faster
  -    // But this is complex, TODO review, run benchmarks 
  +    // Manual state machine instead of a task computation expression, this is visibly faster
       let doMoveNextDiscreteTask(ct:CancellationToken) : Task<bool> =
  -      #if PRERELEASE
  -      Trace.Assert(this.HasValidState)
  -      #endif
         let mutable tcs = Runtime.CompilerServices.AsyncTaskMethodBuilder<bool>.Create() //new TaskCompletionSource<_>() //
         let returnTask = tcs.Task // NB! must access this property first
         let mutable firstStep = ref true
  
positive.code:     along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *)
  
  #nowarn "0086" // operators overloads are intential, Series are as primitive as scalars, all arithmetic operations are defined on them as maps
  namespace Spreads
  
  open System
  
negative.code:           while c.MoveNext() do
              yield c.CurrentValue
          }
  
      override x.Finalize() =
        for v in c.Values do
          v.Dispose()
        c.Dispose()
  
      interface IEnumerable<KeyValuePair<'K, 'V>> with
        member this.GetEnumerator() = this.GetCursor() :> IEnumerator<KeyValuePair<'K, 'V>>
  