SampleAuto.hs

-- | Sample an auto's output when a blip stream outputs something.
--
-- Takes two autos, one which outputs a some value, and another which outputs a
-- blip stream. Produces an auto which outputs a blip with the contents of the
-- first auto whenever the blip stream outputs.
sample :: forall m a b c. (Monad m) =>
            Auto m a c
         -> Auto m a (Blip b)
         -> Auto m a (Blip (b, c))
sample valueAuto blipAuto = onJusts <<< arr extractMaybe <<< ((asMaybes <<< blipAuto) &&& valueAuto)
  where
    extractMaybe :: (Maybe b, c) -> Maybe (b, c)
    extractMaybe (Just b, c) = Just (b, c)
    extractMaybe _ = Nothing

sample = liftA2 $ \x -> fmap (,x)

Functor instance for Blip is usually handy :)