Delay the value of a signal for a specified period of time

Debounce.elm

-- Maybe this should use a `foldp`?

import Graphics.Element exposing (..)
import Mouse
import Time


debounce : Time.Time -> a -> Signal a -> Signal a
debounce after initialValue signal =
  let
    isUpdating = Time.since after signal
    currentValue = Signal.map2 (,) signal isUpdating
    extract (value, updating) =
      case updating of
        True -> Nothing
        False -> Just value
  in
    Signal.filterMap extract initialValue currentValue


debouncePosition =
  debounce (150 * Time.millisecond) (0,0) Mouse.position


main =
  Signal.map show debouncePosition