makeTransducer.idr

makeTransducer :
    s'
    -> (Step s acc b -> Step s (s', acc) a)
    -> (Step s acc b -> s' -> acc -> State s acc)
    -> Transducer acc s (s', s) a b
makeTransducer initialState stepTf onComplete next =
  MkReducer (initialState, state next) stepImpl completeImpl
  where
    completeImpl (s', s) acc =
      let acc = evalState (onComplete (runStep next) s' acc) s
      in complete next s acc
    stepImpl acc x = do
      (s1', s1) <- get
      let (result, s2) = runState (stepTf (runStep next) (s1', acc) x) s1
      case result of
        Done (s2', acc) => do
          put (s2', s2)
          pure (Done acc)
        Continue (s2', acc) => do
          put (s2', s2)
          pure (Continue acc)