//why do i have to cast this to call members that impliment the PriorityQueue interface
type IteratorHeap(inputSeries:List<MergeIterator>) =
interface PriorityQueue with
member self.HasNext = inputSeries.Count > 0 && inputSeries.Item(0).HasNext;
member self.Peek() = new InstrumentDataSeriesObject(instrument, trade)
member self.Dequeue() = new InstrumentDataSeriesObject(instrument, trade)

let empty_list = new List<MergeIterator>()
let iteratorHeap = new IteratorHeap(empty_list)
let queue = iteratorHeap :> PriorityQueue

[<Fact>]
let empty_iterator_has_no_next() = queue.HasNext |> Is false

//but for object espressions, i do not have to cast this to call members that impliment the PriorityQueue interface
let iteratorHeap2 = {new PriorityQueue with
member self.HasNext = false
member self.Peek() = new InstrumentDataSeriesObject(instrument, trade)
member self.Dequeue() = new InstrumentDataSeriesObject(instrument, trade)}

[<Fact>]
let empty_iterator2_has_no_next() = iteratorHeap2.HasNext |> Is false