effect State s where
  get : {State s} s
  set : s -> {State s} ()

effect Console where
  read : {Console} (Optional Text)
  write : Text -> {Console} ()

fst x = case x of Pair.Pair a _ -> a

snd x = case x of Pair.Pair _ (Pair.Pair b _) -> b

namespace Console where

  simulate : Effect Console a -> {State ([Text], [Text])} a
  simulate c = case c of
    {Console.read -> k} ->
      io = State.get
      ins = fst io
      outs = snd io
      State.set (drop 1 ins, outs)
      k (at 0 ins) -- this is missing recursive call to handle
    {Console.write t -> k} ->
      io = State.get
      ins = fst io
      outs = snd io
      k (State.set (ins, cons t outs)) -- this is missing recursive call

()