Async Enumerables and Observables

AsyncSequences.fs

// An Async Enumerator is a getter of Async values. An Async Observer is an Async setter of values
type AsyncEnumerator<'a> = unit -> Async<'a>
type AsyncObserver<'a> = 'a -> Async<unit>

// An Async sequence is a getter of Async Enumerators. An Async Observable is an Async setter of Async Observers
type AsyncSequence<'a> = unit -> AsyncEnumerator<'a>
type AsyncObservable<'a> = AsyncObserver<'a> -> Async<unit>

type AsyncSequence'<'a> = unit -> (unit -> Async<'a>)
type AsyncObservable'<'a> = ('a -> Async<unit>) -> Async<unit>