Idris2/tests/idris2/interactive009/Door.idr

data Usage = Once | Many

data Use : Usage -> (Type -> Type) -> Type -> Type where
     Pure : (1 x : a) -> Use t m a
     BindOnce : (1 act : Use Once m a) -> (1 k : (1 x : a) -> Use t m b) -> Use t m b
     BindMany : (1 act : Use Many m a) -> (1 k : (x : a) -> Use t m b) -> Use t m b

contType : (Type -> Type) -> Usage -> Usage -> Type -> Type -> Type
contType m Once q a b = ((1 x : a) -> Use q m b)
contType m Many q a b = ((x : a) -> Use q m b)

(>>=) : {p : _} -> (1 f : Use p m a) -> (1 k : contType m p q a b) -> Use q m b
(>>=) {p = Once} = BindOnce
(>>=) {p = Many} = BindMany

pure : (1 x : a) -> Use t m a
pure = Pure

One : (Type -> Type) -> Type -> Type
One = Use Once

Any : (Type -> Type) -> Type -> Type
Any = Use Many

infix 2 @@

data Res : (a : Type) -> (a -> Type) -> Type where
     (@@) : (x : a) -> (1 res : r x) -> Res a r

data DoorState = Closed | Open

data Door : DoorState -> Type where
     MkDoor : (isOpen : Bool) -> Door (if isOpen then Open else Closed)

newDoor : One m (Door Closed)
newDoor = pure (MkDoor False)

knock : (1 d : Door Closed) -> One m (Door Closed)
openDoor : (1 d : Door Closed) ->
           One m (Res Bool (\r => Door (if r then Open else Closed)))

closeDoor : (1 d : Door Open) -> One m (Door Closed)

deleteDoor : (1 d : Door Closed) -> Any m ()

doorProg : Any m ()
doorProg
    = do d <- newDoor
         r <- openDoor d
         let x = 42
         case r of
              what => ?now

doorProg2 : Any m ()
doorProg2
    = do d <- newDoor
         r <- openDoor d
         let x = 42
         case r of
              (res @@ d) => ?now_1

doorProg3 : Any m ()
doorProg3
    = do d <- newDoor
         r <- openDoor d
         let x = 42
         case r of
              (True @@ d) => ?now_2
              (False @@ d) => ?now_3