Some Publishers for use with Combine

Concatenate the outputs of a Stream of Publishers.

public struct ConcatenateMany<Publishers: Sequence>: Publisher
  where S.Element: Publisher
{
  public typealias Output =  Publishers.Element.Output
  public typealias Failure = Publishers.Element.Failure

  public init(publishers: Publishers)
}

ConcatenateMany terminates normally (with Completion.finished) only after all its inputs have terminated. The inputs proceed in order, with no interleaving. ConcatenateMany terminates with error on the first error encountered.

Re-subscribes to a Publisher whenever it ends normally (with Completion.finished)

public struct Repeat<Upstream: Publisher>: Publisher
{
  public typealias Output =  Upstream.Output
  public typealias Failure = Upstream.Failure

  public init(publisher: Upstream)
}

Repeat only terminates with an error or after its Subscriber cancels.

Waits for a time interval before requesting the next element from its upstream Publisher

public struct IntervalPublisher<Upstream: Publisher, Context: Scheduler>: Publisher
{
  public typealias Output =  Upstream.Output
  public typealias Failure = Upstream.Failure
  public typealias Interval = Context.SchedulerTimeType.Stride

  public init(publisher: Upstream, scheduler: Context, initialValue: Output? = nil,
              interval: @escaping (_ previous: Output?, _ current: Output) -> Interval,
              initialInterval: @escaping(_ initialValue: Output?) -> Interval = { _ in .seconds(0) })
              
  public init(publisher: Upstream, scheduler: Context, initialValue: Output? = nil, interval: Interval)
}

extension IntervalPublisher where Context == DispatchQueue
{
  public init(publisher: Upstream, qos: DispatchQoS = default, initialValue: Output? = nil,
              interval: @escaping (_ previous: Output?, _ current: Output) -> Interval,
              initialInterval: @escaping(_ initialValue: Output?) -> Interval = { _ in .seconds(0) })

  public init(publisher: Pustream, qos: DispatchQoS = default, initialValue: Output? = nil, interval: Interval)              
}

All requests to the upstream Subscription and deliveries to the downstream Subscriber occur on the same Scheduler.