units.ps

data Zero = Zero

data Succ a = Succ a

pred = \s -> case s of Succ a -> a

meters = \n v -> v { value = n * v.value, meters = Succ (v.meters) }

seconds = \n v -> v { value = n * v.value, seconds = Succ (v.seconds) }

perSecond = \n v -> v { value = n * v.value, seconds = pred (v.seconds)  }

(*.) :: forall r s t. ({ value :: Number | r } -> { value :: Number | s }) -> ({ value :: Number | s } -> { value :: Number | t }) -> { value :: Number | r } -> { value :: Number | t }
(*.) = \n m x -> m (n x)

(+.) :: forall i o. (i -> { value :: Number | o }) -> (i -> { value :: Number | o }) -> i -> { value :: Number | o }
(+.) = \f g x -> do
  var v1 = f x
  var v2 = g x
  return v2 { value = v1.value + v2.value }

test = seconds 1 *. seconds 1

-- fail = seconds 1 +. perSecond 1