Safe Haskell  SafeInferred 

Language  Haskell2010 
This is the central module on which to build upon when constructing Preludes for Polysemy libraries. It reexports most core effects.
Synopsis
 module Incipit.Exception
 module IncipitBase
 embedToFinal :: forall (m :: Type > Type) (r :: [(Type > Type) > Type > Type]) a. (Member (Final m) r, Functor m) => Sem (Embed m ': r) a > Sem r a
 runFinal :: Monad m => Sem '[Final m] a > m a
 embedFinal :: forall m (r :: [(Type > Type) > Type > Type]) a. (Member (Final m) r, Functor m) => m a > Sem r a
 data Final (m :: Type > Type) (z :: Type > Type) a
 transform :: forall e1 e2 (r :: [Effect]) a. Member e2 r => (forall (rInitial :: EffectRow) x. e1 (Sem rInitial) x > e2 (Sem rInitial) x) > Sem (e1 ': r) a > Sem r a
 rewrite :: forall e1 e2 (r :: [Effect]) a. (forall (rInitial :: EffectRow) x. e1 (Sem rInitial) x > e2 (Sem rInitial) x) > Sem (e1 ': r) a > Sem (e2 ': r) a
 interceptH :: forall e (r :: [Effect]) a. Member e r => (forall x (rInitial :: EffectRow). e (Sem rInitial) x > Tactical e (Sem rInitial) r x) > Sem r a > Sem r a
 intercept :: forall e (r :: [Effect]) a. (Member e r, FirstOrder e "intercept") => (forall x (rInitial :: EffectRow). e (Sem rInitial) x > Sem r x) > Sem r a > Sem r a
 reinterpret3 :: forall e1 (e2 :: Effect) (e3 :: Effect) (e4 :: Effect) (r :: [Effect]) a. FirstOrder e1 "reinterpret3" => (forall (rInitial :: EffectRow) x. e1 (Sem rInitial) x > Sem (e2 ': (e3 ': (e4 ': r))) x) > Sem (e1 ': r) a > Sem (e2 ': (e3 ': (e4 ': r))) a
 reinterpret3H :: forall e1 (e2 :: Effect) (e3 :: Effect) (e4 :: Effect) (r :: [Effect]) a. (forall (rInitial :: EffectRow) x. e1 (Sem rInitial) x > Tactical e1 (Sem rInitial) (e2 ': (e3 ': (e4 ': r))) x) > Sem (e1 ': r) a > Sem (e2 ': (e3 ': (e4 ': r))) a
 reinterpret2 :: forall e1 (e2 :: Effect) (e3 :: Effect) (r :: [Effect]) a. FirstOrder e1 "reinterpret2" => (forall (rInitial :: EffectRow) x. e1 (Sem rInitial) x > Sem (e2 ': (e3 ': r)) x) > Sem (e1 ': r) a > Sem (e2 ': (e3 ': r)) a
 reinterpret2H :: forall e1 (e2 :: Effect) (e3 :: Effect) (r :: [Effect]) a. (forall (rInitial :: EffectRow) x. e1 (Sem rInitial) x > Tactical e1 (Sem rInitial) (e2 ': (e3 ': r)) x) > Sem (e1 ': r) a > Sem (e2 ': (e3 ': r)) a
 reinterpret :: forall e1 (e2 :: Effect) (r :: [Effect]) a. FirstOrder e1 "reinterpret" => (forall (rInitial :: EffectRow) x. e1 (Sem rInitial) x > Sem (e2 ': r) x) > Sem (e1 ': r) a > Sem (e2 ': r) a
 reinterpretH :: forall e1 (e2 :: Effect) (r :: [Effect]) a. (forall (rInitial :: EffectRow) x. e1 (Sem rInitial) x > Tactical e1 (Sem rInitial) (e2 ': r) x) > Sem (e1 ': r) a > Sem (e2 ': r) a
 interpretH :: forall e (r :: [Effect]) a. (forall (rInitial :: EffectRow) x. e (Sem rInitial) x > Tactical e (Sem rInitial) r x) > Sem (e ': r) a > Sem r a
 interpret :: forall e (r :: [Effect]) a. FirstOrder e "interpret" => (forall (rInitial :: EffectRow) x. e (Sem rInitial) x > Sem r x) > Sem (e ': r) a > Sem r a
 withLowerToIO :: forall (r :: [(Type > Type) > Type > Type]) a. Member (Embed IO) r => ((forall x. Sem r x > IO x) > IO () > IO a) > Sem r a
 makeSem_ :: Name > Q [Dec]
 makeSem :: Name > Q [Dec]
 bindTSimple :: forall m f (r :: [Effect]) (e :: Effect) a b. (a > m b) > f a > Sem (WithTactics e f m r) (f b)
 bindT :: forall a m b (e :: Effect) f (r :: [Effect]). (a > m b) > Sem (WithTactics e f m r) (f a > Sem (e ': r) (f b))
 runTSimple :: forall m a (e :: Effect) (r :: [Effect]). m a > Tactical e m r a
 runT :: forall m a (e :: Effect) f (r :: [Effect]). m a > Sem (WithTactics e f m r) (Sem (e ': r) (f a))
 pureT :: forall f a (e :: Effect) (m :: Type > Type) (r :: [Effect]). Functor f => a > Sem (WithTactics e f m r) (f a)
 getInspectorT :: forall (e :: Effect) (f :: Type > Type) (m :: Type > Type) (r :: [Effect]). Sem (WithTactics e f m r) (Inspector f)
 getInitialStateT :: forall f (m :: Type > Type) (r :: [Effect]) (e :: Effect). Sem (WithTactics e f m r) (f ())
 type Tactical (e :: Effect) (m :: Type > Type) (r :: [Effect]) x = forall (f :: Type > Type). Functor f => Sem (WithTactics e f m r) (f x)
 type WithTactics (e :: Effect) (f :: Type > Type) (m :: Type > Type) (r :: [Effect]) = (Tactics f m (e ': r) :: (Type > Type) > Type > Type) ': r
 newtype Inspector (f :: Type > Type) = Inspector {}
 (.@@) :: forall m (r :: [Effect]) (e :: Effect) f z. Monad m => (forall x. Sem r x > m x) > (forall y. (forall x. Sem r x > m x) > Sem (e ': r) y > Sem r (f y)) > Sem (e ': r) z > m (f z)
 (.@) :: forall m (r :: [Effect]) (e :: Effect) z. Monad m => (forall x. Sem r x > m x) > (forall y. (forall x. Sem r x > m x) > Sem (e ': r) y > Sem r y) > Sem (e ': r) z > m z
 runM :: Monad m => Sem '[Embed m] a > m a
 embed :: forall m (r :: [(Type > Type) > Type > Type]) a. Member (Embed m) r => m a > Sem r a
 insertAt :: forall (index :: Nat) (inserted :: [Effect]) (head :: [Effect]) (oldTail :: [Effect]) (tail :: [Effect]) (old :: [Effect]) (full :: [Effect]) a. (ListOfLength index head, WhenStuck index (InsertAtUnprovidedIndex :: Constraint), old ~ Append head oldTail, tail ~ Append inserted oldTail, full ~ Append head tail, InsertAtIndex index head tail oldTail full inserted) => Sem old a > Sem full a
 subsume :: forall (e :: Effect) (r :: [Effect]) a. Member e r => Sem (e ': r) a > Sem r a
 subsume_ :: forall (r :: EffectRow) (r' :: EffectRow) a. Subsume r r' => Sem r a > Sem r' a
 raise3Under :: forall (e4 :: Effect) (e1 :: Effect) (e2 :: Effect) (e3 :: Effect) (r :: [Effect]) a. Sem (e1 ': (e2 ': (e3 ': r))) a > Sem (e1 ': (e2 ': (e3 ': (e4 ': r)))) a
 raise2Under :: forall (e3 :: Effect) (e1 :: Effect) (e2 :: Effect) (r :: [Effect]) a. Sem (e1 ': (e2 ': r)) a > Sem (e1 ': (e2 ': (e3 ': r))) a
 raiseUnder3 :: forall (e2 :: Effect) (e3 :: Effect) (e4 :: Effect) (e1 :: Effect) (r :: [Effect]) a. Sem (e1 ': r) a > Sem (e1 ': (e2 ': (e3 ': (e4 ': r)))) a
 raiseUnder2 :: forall (e2 :: Effect) (e3 :: Effect) (e1 :: Effect) (r :: [Effect]) a. Sem (e1 ': r) a > Sem (e1 ': (e2 ': (e3 ': r))) a
 raiseUnder :: forall (e2 :: Effect) (e1 :: Effect) (r :: [Effect]) a. Sem (e1 ': r) a > Sem (e1 ': (e2 ': r)) a
 raise :: forall (e :: Effect) (r :: EffectRow) a. Sem r a > Sem (e ': r) a
 raise_ :: forall (r :: EffectRow) (r' :: EffectRow) a. Raise r r' => Sem r a > Sem r' a
 type family Members (es :: [k]) (r :: [k]) where ...
 type InterpreterFor (e :: Effect) (r :: [Effect]) = forall a. Sem (e ': r) a > Sem r a
 type InterpretersFor (es :: [Effect]) (r :: [Effect]) = forall a. Sem (Append es r) a > Sem r a
 type Member (e :: k) (r :: [k]) = MemberNoError e r
 type MemberWithError (e :: Effect) (r :: [Effect]) = (MemberNoError e r, WhenStuck (LocateEffect e r) (AmbiguousSend e r :: Constraint))
 data Sem (r :: EffectRow) a
 type Effect = (Type > Type) > Type > Type
 type EffectRow = [Effect]
 newtype Embed (m :: Type > Type) (z :: Type > Type) a where
 lowerAsync :: forall (r :: [(Type > Type) > Type > Type]) a. Member (Embed IO) r => (forall x. Sem r x > IO x) > Sem (Async ': r) a > Sem r a
 asyncToIOFinal :: forall (r :: [(Type > Type) > Type > Type]) a. Member (Final IO) r => Sem (Async ': r) a > Sem r a
 asyncToIO :: forall (r :: [(Type > Type) > Type > Type]) a. Member (Embed IO) r => Sem (Async ': r) a > Sem r a
 sequenceConcurrently :: forall t (r :: [(Type > Type) > Type > Type]) a. (Traversable t, Member Async r) => t (Sem r a) > Sem r (t (Maybe a))
 cancel :: forall (r :: [Effect]) a. MemberWithError Async r => Async a > Sem r ()
 await :: forall (r :: [Effect]) a. MemberWithError Async r => Async a > Sem r a
 async :: forall (r :: [Effect]) a. MemberWithError Async r => Sem r a > Sem r (Async (Maybe a))
 data Async (m :: Type > Type) a
 atomicStateToState :: forall s (r :: [(Type > Type) > Type > Type]) a. Member (State s :: (Type > Type) > Type > Type) r => Sem ((AtomicState s :: (Type > Type) > Type > Type) ': r) a > Sem r a
 atomicStateToIO :: forall s (r :: [(Type > Type) > Type > Type]) a. Member (Embed IO) r => s > Sem ((AtomicState s :: (Type > Type) > Type > Type) ': r) a > Sem r (s, a)
 runAtomicStateTVar :: forall (r :: [(Type > Type) > Type > Type]) s a. Member (Embed IO) r => TVar s > Sem ((AtomicState s :: (Type > Type) > Type > Type) ': r) a > Sem r a
 runAtomicStateIORef :: forall s (r :: [(Type > Type) > Type > Type]) a. Member (Embed IO) r => IORef s > Sem ((AtomicState s :: (Type > Type) > Type > Type) ': r) a > Sem r a
 atomicModify' :: forall s (r :: [(Type > Type) > Type > Type]). Member (AtomicState s :: (Type > Type) > Type > Type) r => (s > s) > Sem r ()
 atomicModify :: forall s (r :: [(Type > Type) > Type > Type]). Member (AtomicState s :: (Type > Type) > Type > Type) r => (s > s) > Sem r ()
 atomicPut :: forall s (r :: [(Type > Type) > Type > Type]). Member (AtomicState s :: (Type > Type) > Type > Type) r => s > Sem r ()
 atomicState' :: forall s a (r :: [(Type > Type) > Type > Type]). Member (AtomicState s :: (Type > Type) > Type > Type) r => (s > (s, a)) > Sem r a
 atomicGets :: forall s s' (r :: [(Type > Type) > Type > Type]). Member (AtomicState s :: (Type > Type) > Type > Type) r => (s > s') > Sem r s'
 atomicGet :: forall s (r :: [(Type > Type) > Type > Type]). Member (AtomicState s :: (Type > Type) > Type > Type) r => Sem r s
 atomicState :: forall s a (r :: [(Type > Type) > Type > Type]). Member (AtomicState s :: (Type > Type) > Type > Type) r => (s > (s, a)) > Sem r a
 data AtomicState s (m :: k) a
 lowerError :: forall e (r :: [(Type > Type) > Type > Type]) a. (Typeable e, Member (Embed IO) r) => (forall x. Sem r x > IO x) > Sem ((Error e :: (Type > Type) > Type > Type) ': r) a > Sem r (Either e a)
 errorToIOFinal :: forall e (r :: [(Type > Type) > Type > Type]) a. (Typeable e, Member (Final IO) r) => Sem ((Error e :: (Type > Type) > Type > Type) ': r) a > Sem r (Either e a)
 mapError :: forall e1 e2 (r :: [(Type > Type) > Type > Type]) a. Member (Error e2 :: (Type > Type) > Type > Type) r => (e1 > e2) > Sem ((Error e1 :: (Type > Type) > Type > Type) ': r) a > Sem r a
 runError :: forall e (r :: [(Type > Type) > Type > Type]) a. Sem ((Error e :: (Type > Type) > Type > Type) ': r) a > Sem r (Either e a)
 catchJust :: forall e (r :: [(Type > Type) > Type > Type]) b a. Member (Error e :: (Type > Type) > Type > Type) r => (e > Maybe b) > Sem r a > (b > Sem r a) > Sem r a
 tryJust :: forall e (r :: [(Type > Type) > Type > Type]) b a. Member (Error e :: (Type > Type) > Type > Type) r => (e > Maybe b) > Sem r a > Sem r (Either b a)
 try :: forall e (r :: [(Type > Type) > Type > Type]) a. Member (Error e :: (Type > Type) > Type > Type) r => Sem r a > Sem r (Either e a)
 note :: forall e (r :: [(Type > Type) > Type > Type]) a. Member (Error e :: (Type > Type) > Type > Type) r => e > Maybe a > Sem r a
 fromExceptionSemVia :: forall exc err (r :: [(Type > Type) > Type > Type]) a. (Exception exc, Member (Error err :: (Type > Type) > Type > Type) r, Member (Final IO) r) => (exc > err) > Sem r a > Sem r a
 fromExceptionSem :: forall e (r :: [(Type > Type) > Type > Type]) a. (Exception e, Member (Error e :: (Type > Type) > Type > Type) r, Member (Final IO) r) => Sem r a > Sem r a
 fromExceptionVia :: forall exc err (r :: [(Type > Type) > Type > Type]) a. (Exception exc, Member (Error err :: (Type > Type) > Type > Type) r, Member (Embed IO) r) => (exc > err) > IO a > Sem r a
 fromException :: forall e (r :: [(Type > Type) > Type > Type]) a. (Exception e, Member (Error e :: (Type > Type) > Type > Type) r, Member (Embed IO) r) => IO a > Sem r a
 fromEitherM :: forall e m (r :: [(Type > Type) > Type > Type]) a. (Member (Error e :: (Type > Type) > Type > Type) r, Member (Embed m) r) => m (Either e a) > Sem r a
 fromEither :: forall e (r :: [(Type > Type) > Type > Type]) a. Member (Error e :: (Type > Type) > Type > Type) r => Either e a > Sem r a
 catch :: forall e (r :: [Effect]) a. MemberWithError (Error e :: (Type > Type) > Type > Type) r => Sem r a > (e > Sem r a) > Sem r a
 throw :: forall e (r :: [Effect]) a. MemberWithError (Error e :: (Type > Type) > Type > Type) r => e > Sem r a
 data Error e (m :: k > Type) (a :: k)
 failToEmbed :: forall (m :: Type > Type) (r :: [(Type > Type) > Type > Type]) a. (Member (Embed m) r, MonadFail m) => Sem ((Fail :: (Type > Type) > Type > Type) ': r) a > Sem r a
 failToNonDet :: forall (r :: [(Type > Type) > Type > Type]) a. Member NonDet r => Sem ((Fail :: (Type > Type) > Type > Type) ': r) a > Sem r a
 failToError :: forall e (r :: [(Type > Type) > Type > Type]) a. Member (Error e :: (Type > Type) > Type > Type) r => (String > e) > Sem ((Fail :: (Type > Type) > Type > Type) ': r) a > Sem r a
 runFail :: forall (r :: [(Type > Type) > Type > Type]) a. Sem ((Fail :: (Type > Type) > Type > Type) ': r) a > Sem r (Either String a)
 data Fail (m :: k) (a :: k1)
 runInputSem :: forall i (r :: EffectRow) a. Sem r i > Sem ((Input i :: (Type > Type) > Type > Type) ': r) a > Sem r a
 runInputList :: forall i (r :: [(Type > Type) > Type > Type]) a. [i] > Sem ((Input (Maybe i) :: (Type > Type) > Type > Type) ': r) a > Sem r a
 runInputConst :: forall i (r :: [(Type > Type) > Type > Type]) a. i > Sem ((Input i :: (Type > Type) > Type > Type) ': r) a > Sem r a
 inputs :: forall i j (r :: [(Type > Type) > Type > Type]). Member (Input i :: (Type > Type) > Type > Type) r => (i > j) > Sem r j
 input :: forall i (r :: [Effect]). MemberWithError (Input i :: (Type > Type) > Type > Type) r => Sem r i
 data Input (i :: k) (m :: k1) (a :: k)
 runOutputSem :: forall o (r :: EffectRow) a. (o > Sem r ()) > Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r a
 runOutputBatched :: forall o (r :: [(Type > Type) > Type > Type]) a. Member (Output [o] :: (Type > Type) > Type > Type) r => Int > Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r a
 ignoreOutput :: forall o (r :: [(Type > Type) > Type > Type]) a. Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r a
 outputToIOMonoidAssocR :: forall o m (r :: [(Type > Type) > Type > Type]) a. (Monoid m, Member (Embed IO) r) => (o > m) > Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r (m, a)
 outputToIOMonoid :: forall o m (r :: [(Type > Type) > Type > Type]) a. (Monoid m, Member (Embed IO) r) => (o > m) > Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r (m, a)
 runOutputMonoidTVar :: forall o m (r :: [(Type > Type) > Type > Type]) a. (Monoid m, Member (Embed IO) r) => TVar m > (o > m) > Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r a
 runOutputMonoidIORef :: forall o m (r :: [(Type > Type) > Type > Type]) a. (Monoid m, Member (Embed IO) r) => IORef m > (o > m) > Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r a
 runLazyOutputMonoidAssocR :: forall o m (r :: [(Type > Type) > Type > Type]) a. Monoid m => (o > m) > Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r (m, a)
 runOutputMonoidAssocR :: forall o m (r :: [(Type > Type) > Type > Type]) a. Monoid m => (o > m) > Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r (m, a)
 runLazyOutputMonoid :: forall o m (r :: [(Type > Type) > Type > Type]) a. Monoid m => (o > m) > Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r (m, a)
 runOutputMonoid :: forall o m (r :: [(Type > Type) > Type > Type]) a. Monoid m => (o > m) > Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r (m, a)
 runLazyOutputList :: forall o (r :: [(Type > Type) > Type > Type]) a. Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r ([o], a)
 runOutputList :: forall o (r :: [(Type > Type) > Type > Type]) a. Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r ([o], a)
 output :: forall o (r :: [Effect]). MemberWithError (Output o :: (Type > Type) > Type > Type) r => o > Sem r ()
 data Output o (m :: k) a
 inputToReader :: forall i (r :: [(Type > Type) > Type > Type]) a. Member (Reader i) r => Sem ((Input i :: (Type > Type) > Type > Type) ': r) a > Sem r a
 runReader :: forall i (r :: [(Type > Type) > Type > Type]) a. i > Sem (Reader i ': r) a > Sem r a
 asks :: forall i j (r :: [(Type > Type) > Type > Type]). Member (Reader i) r => (i > j) > Sem r j
 local :: forall i (r :: [Effect]) a. MemberWithError (Reader i) r => (i > i) > Sem r a > Sem r a
 ask :: forall i (r :: [Effect]). MemberWithError (Reader i) r => Sem r i
 data Reader i (m :: Type > Type) a
 resourceToIO :: forall (r :: [(Type > Type) > Type > Type]) a. Member (Embed IO) r => Sem (Resource ': r) a > Sem r a
 runResource :: forall (r :: [(Type > Type) > Type > Type]) a. Sem (Resource ': r) a > Sem r a
 lowerResource :: forall (r :: [(Type > Type) > Type > Type]) a. Member (Embed IO) r => (forall x. Sem r x > IO x) > Sem (Resource ': r) a > Sem r a
 resourceToIOFinal :: forall (r :: [(Type > Type) > Type > Type]) a. Member (Final IO) r => Sem (Resource ': r) a > Sem r a
 onException :: forall (r :: [(Type > Type) > Type > Type]) a b. Member Resource r => Sem r a > Sem r b > Sem r a
 finally :: forall (r :: [(Type > Type) > Type > Type]) a b. Member Resource r => Sem r a > Sem r b > Sem r a
 bracket_ :: forall (r :: [(Type > Type) > Type > Type]) a b c. Member Resource r => Sem r a > Sem r b > Sem r c > Sem r c
 bracketOnError :: forall (r :: [Effect]) a c b. MemberWithError Resource r => Sem r a > (a > Sem r c) > (a > Sem r b) > Sem r b
 bracket :: forall (r :: [Effect]) a c b. MemberWithError Resource r => Sem r a > (a > Sem r c) > (a > Sem r b) > Sem r b
 data Resource (m :: Type > Type) a
 hoistStateIntoStateT :: forall s (r :: [(Type > Type) > Type > Type]) a. Sem ((State s :: (Type > Type) > Type > Type) ': r) a > StateT s (Sem r) a
 stateToST :: forall s st (r :: [(Type > Type) > Type > Type]) a. Member (Embed (ST st)) r => s > Sem ((State s :: (Type > Type) > Type > Type) ': r) a > Sem r (s, a)
 runStateSTRef :: forall s st (r :: [(Type > Type) > Type > Type]) a. Member (Embed (ST st)) r => STRef st s > Sem ((State s :: (Type > Type) > Type > Type) ': r) a > Sem r a
 stateToIO :: forall s (r :: [(Type > Type) > Type > Type]) a. Member (Embed IO) r => s > Sem ((State s :: (Type > Type) > Type > Type) ': r) a > Sem r (s, a)
 runStateIORef :: forall s (r :: [(Type > Type) > Type > Type]) a. Member (Embed IO) r => IORef s > Sem ((State s :: (Type > Type) > Type > Type) ': r) a > Sem r a
 execLazyState :: forall s (r :: [(Type > Type) > Type > Type]) a. s > Sem ((State s :: (Type > Type) > Type > Type) ': r) a > Sem r s
 evalLazyState :: forall s (r :: [(Type > Type) > Type > Type]) a. s > Sem ((State s :: (Type > Type) > Type > Type) ': r) a > Sem r a
 runLazyState :: forall s (r :: [(Type > Type) > Type > Type]) a. s > Sem ((State s :: (Type > Type) > Type > Type) ': r) a > Sem r (s, a)
 execState :: forall s (r :: [(Type > Type) > Type > Type]) a. s > Sem ((State s :: (Type > Type) > Type > Type) ': r) a > Sem r s
 evalState :: forall s (r :: [(Type > Type) > Type > Type]) a. s > Sem ((State s :: (Type > Type) > Type > Type) ': r) a > Sem r a
 runState :: forall s (r :: [(Type > Type) > Type > Type]) a. s > Sem ((State s :: (Type > Type) > Type > Type) ': r) a > Sem r (s, a)
 modify' :: forall s (r :: [(Type > Type) > Type > Type]). Member (State s :: (Type > Type) > Type > Type) r => (s > s) > Sem r ()
 modify :: forall s (r :: [(Type > Type) > Type > Type]). Member (State s :: (Type > Type) > Type > Type) r => (s > s) > Sem r ()
 gets :: forall s a (r :: [(Type > Type) > Type > Type]). Member (State s :: (Type > Type) > Type > Type) r => (s > a) > Sem r a
 put :: forall s (r :: [Effect]). MemberWithError (State s :: (Type > Type) > Type > Type) r => s > Sem r ()
 get :: forall s (r :: [Effect]). MemberWithError (State s :: (Type > Type) > Type > Type) r => Sem r s
 data State s (m :: k) a
 retag :: forall {k1} {k2} (k3 :: k1) (k4 :: k2) (e :: (Type > Type) > Type > Type) (r :: [(Type > Type) > Type > Type]) a. Member (Tagged k4 e) r => Sem (Tagged k3 e ': r) a > Sem r a
 untag :: forall {k1} (k2 :: k1) (e :: (Type > Type) > Type > Type) (r :: [(Type > Type) > Type > Type]) a. Sem (Tagged k2 e ': r) a > Sem (e ': r) a
 tagged :: forall {k1} (k2 :: k1) (e :: Effect) (r :: [Effect]) a. Sem (e ': r) a > Sem (Tagged k2 e ': r) a
 tag :: forall {k1} (k2 :: k1) (e :: (Type > Type) > Type > Type) (r :: [(Type > Type) > Type > Type]) a. Member (Tagged k2 e) r => Sem (e ': r) a > Sem r a
 data Tagged (k3 :: k) (e :: k1 > k2 > Type) (m :: k1) (a :: k2)
 writerToIOAssocRFinal :: forall o (r :: [(Type > Type) > Type > Type]) a. (Monoid o, Member (Final IO) r) => Sem (Writer o ': r) a > Sem r (o, a)
 writerToIOFinal :: forall o (r :: [(Type > Type) > Type > Type]) a. (Monoid o, Member (Final IO) r) => Sem (Writer o ': r) a > Sem r (o, a)
 runWriterTVar :: forall o (r :: [(Type > Type) > Type > Type]) a. (Monoid o, Member (Final IO) r) => TVar o > Sem (Writer o ': r) a > Sem r a
 runLazyWriterAssocR :: forall o (r :: [(Type > Type) > Type > Type]) a. Monoid o => Sem (Writer o ': r) a > Sem r (o, a)
 runWriterAssocR :: forall o (r :: [(Type > Type) > Type > Type]) a. Monoid o => Sem (Writer o ': r) a > Sem r (o, a)
 runLazyWriter :: forall o (r :: [(Type > Type) > Type > Type]) a. Monoid o => Sem (Writer o ': r) a > Sem r (o, a)
 runWriter :: forall o (r :: [(Type > Type) > Type > Type]) a. Monoid o => Sem (Writer o ': r) a > Sem r (o, a)
 outputToWriter :: forall o (r :: [(Type > Type) > Type > Type]) a. Member (Writer o) r => Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r a
 censor :: forall o (r :: [(Type > Type) > Type > Type]) a. Member (Writer o) r => (o > o) > Sem r a > Sem r a
 writerToEndoWriter :: forall o (r :: [(Type > Type) > Type > Type]) a. (Monoid o, Member (Writer (Endo o)) r) => Sem (Writer o ': r) a > Sem r a
 pass :: forall o (r :: [Effect]) a. MemberWithError (Writer o) r => Sem r (o > o, a) > Sem r a
 listen :: forall o (r :: [Effect]) a. MemberWithError (Writer o) r => Sem r a > Sem r (o, a)
 tell :: forall o (r :: [Effect]). MemberWithError (Writer o) r => o > Sem r ()
 data Writer o (m :: Type > Type) a
 type (++) a b = Append a b
 unitT :: Functor f => Sem (WithTactics e f m r) (f ())
 send :: forall e (r :: [(Type > Type) > Type > Type]) a. Member e r => e (Sem r) a > Sem r a
Documentation
module Incipit.Exception
module IncipitBase
embedToFinal :: forall (m :: Type > Type) (r :: [(Type > Type) > Type > Type]) a. (Member (Final m) r, Functor m) => Sem (Embed m ': r) a > Sem r a #
runFinal :: Monad m => Sem '[Final m] a > m a #
Lower a Sem
containing only a single lifted, final Monad
into that
monad.
If you also need to process an
effect, use this together with
Embed
membedToFinal
.
Since: polysemy1.2.0.0
embedFinal :: forall m (r :: [(Type > Type) > Type > Type]) a. (Member (Final m) r, Functor m) => m a > Sem r a #
withWeavingToFinal
admits an implementation of embed
.
Just like embed
, you are discouraged from using this in application code.
Since: polysemy1.2.0.0
data Final (m :: Type > Type) (z :: Type > Type) a #
An effect for embedding higherorder actions in the final target monad of the effect stack.
This is very useful for writing interpreters that interpret higherorder effects in terms of the final monad.
Final
is more powerful than Embed
, but is also less flexible
to interpret (compare runEmbedded
with finalToFinal
).
If you only need the power of embed
, then you should use Embed
instead.
Beware: Final
actions are interpreted as actions of the final monad,
and the effectful state visible to
withWeavingToFinal
/ withStrategicToFinal
/ interpretFinal
is that of all interpreters run in order to produce the final monad.
This means that any interpreter built using Final
will not
respect local/global state semantics based on the order of
interpreters run. You should signal interpreters that make use of
Final
by adding a 
suffix to the names of these.Final
State semantics of effects that are not interpreted in terms of the final monad will always appear local to effects that are interpreted in terms of the final monad.
State semantics between effects that are interpreted in terms of the final monad depend on the final monad. For example, if the final monad is a monad transformer stack, then state semantics will depend on the order monad transformers are stacked.
Since: polysemy1.2.0.0
Instances
type DefiningModule Final  
Defined in Polysemy.Final 
transform :: forall e1 e2 (r :: [Effect]) a. Member e2 r => (forall (rInitial :: EffectRow) x. e1 (Sem rInitial) x > e2 (Sem rInitial) x) > Sem (e1 ': r) a > Sem r a #
Transform an effect e1
into an effect e2
that is already somewhere
inside of the stack.
Since: polysemy1.2.3.0
rewrite :: forall e1 e2 (r :: [Effect]) a. (forall (rInitial :: EffectRow) x. e1 (Sem rInitial) x > e2 (Sem rInitial) x) > Sem (e1 ': r) a > Sem (e2 ': r) a #
Rewrite an effect e1
directly into e2
, and put it on the top of the
effect stack.
Since: polysemy1.2.3.0
:: forall e (r :: [Effect]) a. (Member e r, FirstOrder e "intercept")  
=> (forall x (rInitial :: EffectRow). e (Sem rInitial) x > Sem r x)  A natural transformation from the handled effect to other effects
already in 
> Sem r a  
> Sem r a 
Like interpret
, but instead of handling the effect, allows responding to
the effect while leaving it unhandled. This allows you, for example, to
intercept other effects and insert logic around them.
:: forall e1 (e2 :: Effect) (e3 :: Effect) (e4 :: Effect) (r :: [Effect]) a. FirstOrder e1 "reinterpret3"  
=> (forall (rInitial :: EffectRow) x. e1 (Sem rInitial) x > Sem (e2 ': (e3 ': (e4 ': r))) x)  A natural transformation from the handled effect to the new effects. 
> Sem (e1 ': r) a  
> Sem (e2 ': (e3 ': (e4 ': r))) a 
Like reinterpret
, but introduces three intermediary effects.
:: forall e1 (e2 :: Effect) (e3 :: Effect) (e4 :: Effect) (r :: [Effect]) a. (forall (rInitial :: EffectRow) x. e1 (Sem rInitial) x > Tactical e1 (Sem rInitial) (e2 ': (e3 ': (e4 ': r))) x)  A natural transformation from the handled effect to the new effects. 
> Sem (e1 ': r) a  
> Sem (e2 ': (e3 ': (e4 ': r))) a 
Like reinterpret3
, but for higherorder effects.
See the notes on Tactical
for how to use this function.
:: forall e1 (e2 :: Effect) (e3 :: Effect) (r :: [Effect]) a. FirstOrder e1 "reinterpret2"  
=> (forall (rInitial :: EffectRow) x. e1 (Sem rInitial) x > Sem (e2 ': (e3 ': r)) x)  A natural transformation from the handled effect to the new effects. 
> Sem (e1 ': r) a  
> Sem (e2 ': (e3 ': r)) a 
Like reinterpret
, but introduces two intermediary effects.
:: forall e1 (e2 :: Effect) (e3 :: Effect) (r :: [Effect]) a. (forall (rInitial :: EffectRow) x. e1 (Sem rInitial) x > Tactical e1 (Sem rInitial) (e2 ': (e3 ': r)) x)  A natural transformation from the handled effect to the new effects. 
> Sem (e1 ': r) a  
> Sem (e2 ': (e3 ': r)) a 
Like reinterpret2
, but for higherorder effects.
See the notes on Tactical
for how to use this function.
:: forall e1 (e2 :: Effect) (r :: [Effect]) a. FirstOrder e1 "reinterpret"  
=> (forall (rInitial :: EffectRow) x. e1 (Sem rInitial) x > Sem (e2 ': r) x)  A natural transformation from the handled effect to the new effect. 
> Sem (e1 ': r) a  
> Sem (e2 ': r) a 
Like interpret
, but instead of removing the effect e
, reencodes it in
some new effect f
. This function will fuse when followed by
runState
, meaning it's free to reinterpret
in terms of
the State
effect and immediately run it.
:: forall e1 (e2 :: Effect) (r :: [Effect]) a. (forall (rInitial :: EffectRow) x. e1 (Sem rInitial) x > Tactical e1 (Sem rInitial) (e2 ': r) x)  A natural transformation from the handled effect to the new effect. 
> Sem (e1 ': r) a  
> Sem (e2 ': r) a 
Like reinterpret
, but for higherorder effects.
See the notes on Tactical
for how to use this function.
:: forall e (r :: [Effect]) a. FirstOrder e "interpret"  
=> (forall (rInitial :: EffectRow) x. e (Sem rInitial) x > Sem r x)  A natural transformation from the handled effect to other effects
already in 
> Sem (e ': r) a  
> Sem r a 
The simplest way to produce an effect handler. Interprets an effect e
by
transforming it into other effects inside of r
.
:: forall (r :: [(Type > Type) > Type > Type]) a. Member (Embed IO) r  
=> ((forall x. Sem r x > IO x) > IO () > IO a)  A lambda that takes the lowering function, and a finalizing 
> Sem r a 
Run an effect stack all the way down to IO
by running it in a new
thread, and temporarily turning the current thread into an event poll.
This function creates a thread, and so should be compiled with threaded
.
Since: polysemy0.5.0.0
Like makeSem
, but does not provide type signatures and fixities. This
can be used to attach Haddock comments to individual arguments for each
generated function.
data Output o m a where Output :: o > Output o m () makeSem_ ''Output   Output the value @o@. output :: forall o r . Member (Output o) r => o  ^ Value to output. > Sem r ()  ^ No result.
Because of limitations in Template Haskell, signatures have to follow some rules to work properly:
makeSem_
must be used before the explicit type signatures signatures have to specify argument of
Sem
representing union of effects asr
(e.g.
)Sem
r ()  all arguments in effect's type constructor have to follow naming scheme from data constructor's declaration:
data Foo e m a where FooC1 :: Foo x m () FooC2 :: Foo (Maybe x) m ()
should have x
in type signature of fooC1
:
fooC1 :: forall x r. Member (Foo x) r => Sem r ()
and Maybe x
in signature of fooC2
:
fooC2 :: forall x r. Member (Foo (Maybe x)) r => Sem r ()
 all effect's type variables and
r
have to be explicitly quantified usingforall
(order is not important)
These restrictions may be removed in the future, depending on changes to the compiler.
Change in (TODO(Sandy): version): in case of GADTs, signatures now only use names from data constructor's type and not from type constructor declaration.
Since: polysemy0.1.2.0
If T
is a GADT representing an effect algebra, as described in the
module documentation for Polysemy, $(
automatically
generates a smart constructor for every data constructor of makeSem
''T)T
. This also
works for data family instances. Names of smart constructors are created by
changing first letter to lowercase or removing prefix :
in case of
operators. Fixity declaration is preserved for both normal names and
operators.
Since: polysemy0.1.2.0
:: forall m f (r :: [Effect]) (e :: Effect) a b. (a > m b)  The monadic continuation to lift. This is usually a parameter in your effect. Continuations executed via 
> f a  
> Sem (WithTactics e f m r) (f b) 
Lift a kleisli action into the stateful environment.
You can use bindTSimple
to execute an effect parameter of the form
a > m b
by providing the result of a runTSimple
or another
bindTSimple
.
This is a less flexible but significantly simpler variant of bindT
.
Instead of returning a Sem
kleisli action corresponding to the
provided kleisli action, bindTSimple
runs the kleisli action immediately.
Since: polysemy1.5.0.0
:: forall m a (e :: Effect) (r :: [Effect]). m a  The monadic action to lift. This is usually a parameter in your effect. 
> Tactical e m r a 
Run a monadic action in a Tactical
environment. The stateful environment
used will be the same one that the effect is initally run in.
Use bindTSimple
if you'd prefer to explicitly manage your stateful
environment.
This is a less flexible but significantly simpler variant of runT
.
Instead of returning a Sem
action corresponding to the provided action,
runTSimple
runs the action immediately.
Since: polysemy1.5.0.0
:: forall m a (e :: Effect) f (r :: [Effect]). m a  The monadic action to lift. This is usually a parameter in your effect. 
> Sem (WithTactics e f m r) (Sem (e ': r) (f a)) 
pureT :: forall f a (e :: Effect) (m :: Type > Type) (r :: [Effect]). Functor f => a > Sem (WithTactics e f m r) (f a) #
Lift a value into Tactical
.
getInspectorT :: forall (e :: Effect) (f :: Type > Type) (m :: Type > Type) (r :: [Effect]). Sem (WithTactics e f m r) (Inspector f) #
Get a natural transformation capable of potentially inspecting values
inside of f
. Binding the result of getInspectorT
produces a function that
can sometimes peek inside values returned by bindT
.
This is often useful for running callback functions that are not managed by polysemy code.
Example
We can use the result of getInspectorT
to "undo" pureT
(or any of the other
Tactical
functions):
ins <getInspectorT
fa <pureT
"hello" fb <pureT
True let a =inspect
ins fa  Just "hello" b =inspect
ins fb  Just True
getInitialStateT :: forall f (m :: Type > Type) (r :: [Effect]) (e :: Effect). Sem (WithTactics e f m r) (f ()) #
type Tactical (e :: Effect) (m :: Type > Type) (r :: [Effect]) x = forall (f :: Type > Type). Functor f => Sem (WithTactics e f m r) (f x) #
Tactical
is an environment in which you're capable of explicitly
threading higherorder effect states. This is provided by the (internal)
effect Tactics
, which is capable of rewriting monadic actions so they run
in the correct stateful environment.
Inside a Tactical
, you're capable of running pureT
, runT
and bindT
which are the main tools for rewriting monadic stateful environments.
For example, consider trying to write an interpreter for
Resource
, whose effect is defined as:
dataResource
m a whereBracket
:: m a > (a > m ()) > (a > m b) >Resource
m b
Here we have an m a
which clearly needs to be run first, and then
subsequently call the a > m ()
and a > m b
arguments. In a Tactical
environment, we can write the threading code thusly:
Bracket
alloc dealloc use > do alloc' <runT
alloc dealloc' <bindT
dealloc use' <bindT
use
where
alloc' ::Sem
(Resource
': r) (f a1) dealloc' :: f a1 >Sem
(Resource
': r) (f ()) use' :: f a1 >Sem
(Resource
': r) (f x)
The f
type here is existential and corresponds to "whatever
state the other effects want to keep track of." f
is always
a Functor
.
alloc'
, dealloc'
and use'
are now in a form that can be
easily consumed by your interpreter. At this point, simply bind
them in the desired order and continue on your merry way.
We can see from the types of dealloc'
and use'
that since they both
consume a f a1
, they must run in the same stateful environment. This
means, for illustration, any put
s run inside the use
block will not be visible inside of the dealloc
block.
Power users may explicitly use getInitialStateT
and bindT
to construct
whatever data flow they'd like; although this is usually unnecessary.
type WithTactics (e :: Effect) (f :: Type > Type) (m :: Type > Type) (r :: [Effect]) = (Tactics f m (e ': r) :: (Type > Type) > Type > Type) ': r #
newtype Inspector (f :: Type > Type) #
A container for inspect
. See the documentation for getInspectorT
.
Inspector  

:: forall m (r :: [Effect]) (e :: Effect) f z. Monad m  
=> (forall x. Sem r x > m x)  The lowering function, likely 
> (forall y. (forall x. Sem r x > m x) > Sem (e ': r) y > Sem r (f y))  
> Sem (e ': r) z  
> m (f z) 
Like .@
, but for interpreters which change the resulting type  eg.
lowerError
.
:: forall m (r :: [Effect]) (e :: Effect) z. Monad m  
=> (forall x. Sem r x > m x)  The lowering function, likely 
> (forall y. (forall x. Sem r x > m x) > Sem (e ': r) y > Sem r y)  
> Sem (e ': r) z  
> m z 
Some interpreters need to be able to lower down to the base monad (often
IO
) in order to function properly  some good examples of this are
lowerError
and lowerResource
.
However, these interpreters don't compose particularly nicely; for example,
to run lowerResource
, you must write:
runM . lowerError runM
Notice that runM
is duplicated in two places here. The situation gets
exponentially worse the more intepreters you have that need to run in this
pattern.
Instead, .@
performs the composition we'd like. The above can be written as
(runM .@ lowerError)
The parentheses here are important; without them you'll run into operator precedence errors.
Warning: This combinator will duplicate work that is intended to be
just for initialization. This can result in rather surprising behavior. For
a version of .@
that won't duplicate work, see the .@!
operator in
polysemyzoo.
Interpreters using Final
may be composed normally, and
avoid the work duplication issue. For that reason, you're encouraged to use

interpreters instead of Final
lower
interpreters whenever
possible.
embed :: forall m (r :: [(Type > Type) > Type > Type]) a. Member (Embed m) r => m a > Sem r a #
Embed a monadic action m
in Sem
.
Since: polysemy1.0.0.0
insertAt :: forall (index :: Nat) (inserted :: [Effect]) (head :: [Effect]) (oldTail :: [Effect]) (tail :: [Effect]) (old :: [Effect]) (full :: [Effect]) a. (ListOfLength index head, WhenStuck index (InsertAtUnprovidedIndex :: Constraint), old ~ Append head oldTail, tail ~ Append inserted oldTail, full ~ Append head tail, InsertAtIndex index head tail oldTail full inserted) => Sem old a > Sem full a #
Introduce a set of effects into Sem
at the index i
, before the effect
that previously occupied that position. This is intended to be used with a
type application:
let sem1 :: Sem [e1, e2, e3, e4, e5] a sem1 = insertAt @2 (sem0 :: Sem [e1, e2, e5] a)
Since: polysemy1.6.0.0
subsume :: forall (e :: Effect) (r :: [Effect]) a. Member e r => Sem (e ': r) a > Sem r a #
Interprets an effect in terms of another identical effect.
This is useful for defining interpreters that use reinterpretH
without immediately consuming the newly introduced effect.
Using such an interpreter recursively may result in duplicate effects,
which may then be eliminated using subsume
.
For a version that can introduce an arbitrary number of new effects and
reorder existing ones, see subsume_
.
Since: polysemy1.2.0.0
subsume_ :: forall (r :: EffectRow) (r' :: EffectRow) a. Subsume r r' => Sem r a > Sem r' a #
Allows reordering and adding known effects on top of the effect stack, as
long as the polymorphic "tail" of new stack is a raise
d version of the
original one. This function is highly polymorphic, so it may be a good idea
to use its more concrete version (subsume
), fitting functions from the
raise
family or type annotations to avoid vague errors in ambiguous
contexts.
Since: polysemy1.4.0.0
raise3Under :: forall (e4 :: Effect) (e1 :: Effect) (e2 :: Effect) (e3 :: Effect) (r :: [Effect]) a. Sem (e1 ': (e2 ': (e3 ': r))) a > Sem (e1 ': (e2 ': (e3 ': (e4 ': r)))) a #
Like raise
, but introduces an effect three levels underneath the head
of the list.
Since: polysemy1.4.0.0
raise2Under :: forall (e3 :: Effect) (e1 :: Effect) (e2 :: Effect) (r :: [Effect]) a. Sem (e1 ': (e2 ': r)) a > Sem (e1 ': (e2 ': (e3 ': r))) a #
Like raise
, but introduces an effect two levels underneath the head of
the list.
Since: polysemy1.4.0.0
raiseUnder3 :: forall (e2 :: Effect) (e3 :: Effect) (e4 :: Effect) (e1 :: Effect) (r :: [Effect]) a. Sem (e1 ': r) a > Sem (e1 ': (e2 ': (e3 ': (e4 ': r)))) a #
Like raise
, but introduces three new effects underneath the head of the
list.
Since: polysemy1.2.0.0
raiseUnder2 :: forall (e2 :: Effect) (e3 :: Effect) (e1 :: Effect) (r :: [Effect]) a. Sem (e1 ': r) a > Sem (e1 ': (e2 ': (e3 ': r))) a #
Like raise
, but introduces two new effects underneath the head of the
list.
Since: polysemy1.2.0.0
raiseUnder :: forall (e2 :: Effect) (e1 :: Effect) (r :: [Effect]) a. Sem (e1 ': r) a > Sem (e1 ': (e2 ': r)) a #
Like raise
, but introduces a new effect underneath the head of the
list. See raiseUnder2
or raiseUnder3
for introducing more effects. If
you need to introduce even more of them, check out subsume_
.
raiseUnder
can be used in order to turn transformative interpreters
into reinterpreters. This is especially useful if you're writing an
interpreter which introduces an intermediary effect, and then want to use
an existing interpreter on that effect.
For example, given:
fooToBar ::Member
Bar r =>Sem
(Foo ': r) a >Sem
r a runBar ::Sem
(Bar ': r) a >Sem
r a
You can write:
runFoo ::Sem
(Foo ': r) a >Sem
r a runFoo = runBar  Consume Bar . fooToBar  Interpret Foo in terms of the new Bar .raiseUnder
 Introduces Bar under Foo
Since: polysemy1.2.0.0
raise_ :: forall (r :: EffectRow) (r' :: EffectRow) a. Raise r r' => Sem r a > Sem r' a #
Introduce an arbitrary number of effects on top of the effect stack. This
function is highly polymorphic, so it may be good idea to use its more
concrete versions (like raise
) or type annotations to avoid vague errors
in ambiguous contexts.
Since: polysemy1.4.0.0
type family Members (es :: [k]) (r :: [k]) where ... #
Makes constraints of functions that use multiple effects shorter by
translating single list of effects into multiple Member
constraints:
foo ::Members
'[Output
Int ,Output
Bool ,State
String ] r =>Sem
r ()
translates into:
foo :: (Member
(Output
Int) r ,Member
(Output
Bool) r ,Member
(State
String) r ) =>Sem
r ()
Since: polysemy0.1.2.0
type InterpreterFor (e :: Effect) (r :: [Effect]) = forall a. Sem (e ': r) a > Sem r a #
Type synonym for interpreters that consume an effect without changing the return value. Offered for user convenience.
r
Is kept polymorphic so it's possible to place constraints upon it:
teletypeToIO ::Member
(Embed IO) r =>InterpreterFor
Teletype r
type InterpretersFor (es :: [Effect]) (r :: [Effect]) = forall a. Sem (Append es r) a > Sem r a #
Variant of InterpreterFor
that takes a list of effects.
@since 1.5.0.0
type Member (e :: k) (r :: [k]) = MemberNoError e r #
A proof that the effect e
is available somewhere inside of the effect
stack r
.
type MemberWithError (e :: Effect) (r :: [Effect]) = (MemberNoError e r, WhenStuck (LocateEffect e r) (AmbiguousSend e r :: Constraint)) #
Like Member
, but will produce an error message if the types are
ambiguous. This is the constraint used for actions generated by
makeSem
.
Be careful with this. Due to quirks of TypeError
,
the custom error messages emitted by this can potentially override other,
more helpful error messages.
See the discussion in
Issue #227.
Since: polysemy1.2.3.0
The Sem
monad handles computations of arbitrary extensible effects.
A value of type Sem r
describes a program with the capabilities of
r
. For best results, r
should always be kept polymorphic, but you can
add capabilities via the Member
constraint.
The value of the Sem
monad is that it allows you to write programs
against a set of effects without a predefined meaning, and provide that
meaning later. For example, unlike with mtl, you can decide to interpret an
Error
effect traditionally as an Either
, or instead
as (a significantly faster) IO
Exception
. These
interpretations (and others that you might add) may be used interchangeably
without needing to write any newtypes or Monad
instances. The only
change needed to swap interpretations is to change a call from
runError
to errorToIOFinal
.
The effect stack r
can contain arbitrary other monads inside of it. These
monads are lifted into effects via the Embed
effect. Monadic values can be
lifted into a Sem
via embed
.
Higherorder actions of another monad can be lifted into higherorder actions
of Sem
via the Final
effect, which is more powerful
than Embed
, but also less flexible to interpret.
A Sem
can be interpreted as a pure value (via run
) or as any
traditional Monad
(via runM
or runFinal
).
Each effect E
comes equipped with some interpreters of the form:
runE ::Sem
(E ': r) a >Sem
r a
which is responsible for removing the effect E
from the effect stack. It
is the order in which you call the interpreters that determines the
monomorphic representation of the r
parameter.
Order of interpreters can be important  it determines behaviour of effects that manipulate state or change control flow. For example, when interpreting this action:
>>>
:{
example :: Members '[State String, Error String] r => Sem r String example = do put "start" let throwing, catching :: Members '[State String, Error String] r => Sem r String throwing = do modify (++"throw") throw "error" get catching = do modify (++"catch") get catch @String throwing (\ _ > catching) :}
when handling Error
first, state is preserved after error
occurs:
>>>
:{
example & runError & fmap (either id id) & evalState "" & runM & (print =<<) :} "startthrowcatch"
while handling State
first discards state in such cases:
>>>
:{
example & evalState "" & runError & fmap (either id id) & runM & (print =<<) :} "startcatch"
A good rule of thumb is to handle effects which should have "global" behaviour over other effects later in the chain.
After all of your effects are handled, you'll be left with either
a
, a Sem
'[] a
, or a Sem
'[ Embed
m ] a
value, which can be consumed respectively by Sem
'[ Final
m ] arun
, runM
, and
runFinal
.
Examples
As an example of keeping r
polymorphic, we can consider the type
Member
(State
String) r =>Sem
r ()
to be a program with access to
get
::Sem
r Stringput
:: String >Sem
r ()
methods.
By also adding a
Member
(Error
Bool) r
constraint on r
, we gain access to the
throw
:: Bool >Sem
r acatch
::Sem
r a > (Bool >Sem
r a) >Sem
r a
functions as well.
In this sense, a
constraint is
analogous to mtl's Member
(State
s) r
and should
be thought of as such. However, unlike mtl, a MonadState
s mSem
monad may have
an arbitrary number of the same effect.
For example, we can write a Sem
program which can output either
Int
s or Bool
s:
foo :: (Member
(Output
Int) r ,Member
(Output
Bool) r ) =>Sem
r () foo = dooutput
@Int 5output
True
Notice that we must use XTypeApplications
to specify that we'd like to
use the (Output
Int
) effect.
Since: polysemy0.1.2.0
Instances
Member (Fail :: (Type > Type) > Type > Type) r => MonadFail (Sem r)  Since: polysemy1.1.0.0 
Defined in Polysemy.Internal  
Member Fixpoint r => MonadFix (Sem r)  
Defined in Polysemy.Internal  
Member (Embed IO) r => MonadIO (Sem r)  This instance will only lift 
Defined in Polysemy.Internal  
Member NonDet r => Alternative (Sem r)  
Applicative (Sem f)  
Functor (Sem f)  
Monad (Sem f)  
Member NonDet r => MonadPlus (Sem r)  Since: polysemy0.2.1.0 
Monoid a => Monoid (Sem f a)  Since: polysemy1.6.0.0 
Semigroup a => Semigroup (Sem f a)  Since: polysemy1.6.0.0 
newtype Embed (m :: Type > Type) (z :: Type > Type) a where #
An effect which allows a regular Monad
m
into the Sem
ecosystem. Monadic actions in m
can be lifted into Sem
via
embed
.
For example, you can use this effect to lift IO
actions directly into
Sem
:
embed
(putStrLn "hello") ::Member
(Embed
IO) r =>Sem
r ()
That being said, you lose out on a significant amount of the benefits of
Sem
by using embed
directly in application code; doing
so will tie your application code directly to the underlying monad, and
prevent you from interpreting it differently. For best results, only use
Embed
in your effect interpreters.
Consider using trace
and traceToIO
as
a substitute for using putStrLn
directly.
Since: polysemy1.0.0.0
asyncToIOFinal :: forall (r :: [(Type > Type) > Type > Type]) a. Member (Final IO) r => Sem (Async ': r) a > Sem r a #
Run an Async
effect in terms of async
through final IO
.
Beware: Effects that aren't interpreted in terms of IO
will have local state semantics in regards to Async
effects
interpreted this way. See Final
.
Notably, unlike asyncToIO
, this is not consistent with
State
unless runStateIORef
is used.
State that seems like it should be threaded globally throughout Async
will not be.
Use asyncToIO
instead if you need to run
pure, stateful interpreters after the interpreter for Async
.
(Pure interpreters are interpreters that aren't expressed in terms of
another effect or monad; for example, runState
.)
Since: polysemy1.2.0.0
asyncToIO :: forall (r :: [(Type > Type) > Type > Type]) a. Member (Embed IO) r => Sem (Async ': r) a > Sem r a #
A more flexible  though less performant 
version of asyncToIOFinal
.
This function is capable of running Async
effects anywhere within an
effect stack, without relying on Final
to lower it into IO
.
Notably, this means that State
effects will be consistent
in the presence of Async
.
asyncToIO
is unsafe if you're using await
inside higherorder actions
of other effects interpreted after Async
.
See Issue #205.
Prefer asyncToIOFinal
unless you need to run pure, stateful interpreters
after the interpreter for Async
.
(Pure interpreters are interpreters that aren't expressed in terms of
another effect or monad; for example, runState
.)
Since: polysemy1.0.0.0
sequenceConcurrently :: forall t (r :: [(Type > Type) > Type > Type]) a. (Traversable t, Member Async r) => t (Sem r a) > Sem r (t (Maybe a)) #
Perform a sequence of effectful actions concurrently.
Since: polysemy1.2.2.0
data Async (m :: Type > Type) a #
An effect for spawning asynchronous computations.
The Maybe
returned by async
is due to the fact that we can't be sure an
Error
effect didn't fail locally.
Since: polysemy0.5.0.0
Instances
type DefiningModule Async  
Defined in Polysemy.Async 
atomicStateToState :: forall s (r :: [(Type > Type) > Type > Type]) a. Member (State s :: (Type > Type) > Type > Type) r => Sem ((AtomicState s :: (Type > Type) > Type > Type) ': r) a > Sem r a #
Transform an AtomicState
effect to a State
effect, discarding
the notion of atomicity.
atomicStateToIO :: forall s (r :: [(Type > Type) > Type > Type]) a. Member (Embed IO) r => s > Sem ((AtomicState s :: (Type > Type) > Type > Type) ': r) a > Sem r (s, a) #
Run an AtomicState
effect in terms of atomic operations
in IO
.
Internally, this simply creates a new IORef
, passes it to
runAtomicStateIORef
, and then returns the result and the final value
of the IORef
.
Beware: As this uses an IORef
internally,
all other effects will have local
state semantics in regards to AtomicState
effects
interpreted this way.
For example, throw
and catch
will
never revert atomicModify
s, even if runError
is used
after atomicStateToIO
.
Since: polysemy1.2.0.0
runAtomicStateTVar :: forall (r :: [(Type > Type) > Type > Type]) s a. Member (Embed IO) r => TVar s > Sem ((AtomicState s :: (Type > Type) > Type > Type) ': r) a > Sem r a #
Run an AtomicState
effect by transforming it into atomic operations
over a TVar
.
runAtomicStateIORef :: forall s (r :: [(Type > Type) > Type > Type]) a. Member (Embed IO) r => IORef s > Sem ((AtomicState s :: (Type > Type) > Type > Type) ': r) a > Sem r a #
Run an AtomicState
effect by transforming it into atomic operations
over an IORef
.
atomicModify' :: forall s (r :: [(Type > Type) > Type > Type]). Member (AtomicState s :: (Type > Type) > Type > Type) r => (s > s) > Sem r () #
A variant of atomicModify
in which the computation is strict in the
new state.
atomicModify :: forall s (r :: [(Type > Type) > Type > Type]). Member (AtomicState s :: (Type > Type) > Type > Type) r => (s > s) > Sem r () #
atomicPut :: forall s (r :: [(Type > Type) > Type > Type]). Member (AtomicState s :: (Type > Type) > Type > Type) r => s > Sem r () #
atomicState' :: forall s a (r :: [(Type > Type) > Type > Type]). Member (AtomicState s :: (Type > Type) > Type > Type) r => (s > (s, a)) > Sem r a #
A variant of atomicState
in which the computation is strict in the new
state and return value.
atomicGets :: forall s s' (r :: [(Type > Type) > Type > Type]). Member (AtomicState s :: (Type > Type) > Type > Type) r => (s > s') > Sem r s' #
Since: polysemy1.2.2.0
atomicGet :: forall s (r :: [(Type > Type) > Type > Type]). Member (AtomicState s :: (Type > Type) > Type > Type) r => Sem r s #
atomicState :: forall s a (r :: [(Type > Type) > Type > Type]). Member (AtomicState s :: (Type > Type) > Type > Type) r => (s > (s, a)) > Sem r a #
Atomically reads and modifies the state.
data AtomicState s (m :: k) a #
A variant of State
that supports atomic operations.
Since: polysemy1.1.0.0
Instances
type DefiningModule (AtomicState :: Type > k > Type > Type)  
Defined in Polysemy.AtomicState 
:: forall e (r :: [(Type > Type) > Type > Type]) a. (Typeable e, Member (Embed IO) r)  
=> (forall x. Sem r x > IO x)  Strategy for lowering a 
> Sem ((Error e :: (Type > Type) > Type > Type) ': r) a  
> Sem r (Either e a) 
errorToIOFinal :: forall e (r :: [(Type > Type) > Type > Type]) a. (Typeable e, Member (Final IO) r) => Sem ((Error e :: (Type > Type) > Type > Type) ': r) a > Sem r (Either e a) #
mapError :: forall e1 e2 (r :: [(Type > Type) > Type > Type]) a. Member (Error e2 :: (Type > Type) > Type > Type) r => (e1 > e2) > Sem ((Error e1 :: (Type > Type) > Type > Type) ': r) a > Sem r a #
Transform one Error
into another. This function can be used to aggregate
multiple errors into a single type.
Since: polysemy1.0.0.0
runError :: forall e (r :: [(Type > Type) > Type > Type]) a. Sem ((Error e :: (Type > Type) > Type > Type) ': r) a > Sem r (Either e a) #
tryJust :: forall e (r :: [(Type > Type) > Type > Type]) b a. Member (Error e :: (Type > Type) > Type > Type) r => (e > Maybe b) > Sem r a > Sem r (Either b a) #
try :: forall e (r :: [(Type > Type) > Type > Type]) a. Member (Error e :: (Type > Type) > Type > Type) r => Sem r a > Sem r (Either e a) #
note :: forall e (r :: [(Type > Type) > Type > Type]) a. Member (Error e :: (Type > Type) > Type > Type) r => e > Maybe a > Sem r a #
fromExceptionSemVia :: forall exc err (r :: [(Type > Type) > Type > Type]) a. (Exception exc, Member (Error err :: (Type > Type) > Type > Type) r, Member (Final IO) r) => (exc > err) > Sem r a > Sem r a #
Like fromExceptionSem
, but with the ability to transform the exception
before turning it into an Error
.
fromExceptionSem :: forall e (r :: [(Type > Type) > Type > Type]) a. (Exception e, Member (Error e :: (Type > Type) > Type > Type) r, Member (Final IO) r) => Sem r a > Sem r a #
fromExceptionVia :: forall exc err (r :: [(Type > Type) > Type > Type]) a. (Exception exc, Member (Error err :: (Type > Type) > Type > Type) r, Member (Embed IO) r) => (exc > err) > IO a > Sem r a #
Like fromException
, but with the ability to transform the exception
before turning it into an Error
.
fromException :: forall e (r :: [(Type > Type) > Type > Type]) a. (Exception e, Member (Error e :: (Type > Type) > Type > Type) r, Member (Embed IO) r) => IO a > Sem r a #
fromEitherM :: forall e m (r :: [(Type > Type) > Type > Type]) a. (Member (Error e :: (Type > Type) > Type > Type) r, Member (Embed m) r) => m (Either e a) > Sem r a #
A combinator doing embed
and fromEither
at the same time. Useful for
interoperating with IO
.
Since: polysemy0.5.1.0
fromEither :: forall e (r :: [(Type > Type) > Type > Type]) a. Member (Error e :: (Type > Type) > Type > Type) r => Either e a > Sem r a #
catch :: forall e (r :: [Effect]) a. MemberWithError (Error e :: (Type > Type) > Type > Type) r => Sem r a > (e > Sem r a) > Sem r a #
throw :: forall e (r :: [Effect]) a. MemberWithError (Error e :: (Type > Type) > Type > Type) r => e > Sem r a #
data Error e (m :: k > Type) (a :: k) #
Instances
type DefiningModule (Error :: Type > (k > Type) > k > Type)  
Defined in Polysemy.Error 
failToEmbed :: forall (m :: Type > Type) (r :: [(Type > Type) > Type > Type]) a. (Member (Embed m) r, MonadFail m) => Sem ((Fail :: (Type > Type) > Type > Type) ': r) a > Sem r a #
failToNonDet :: forall (r :: [(Type > Type) > Type > Type]) a. Member NonDet r => Sem ((Fail :: (Type > Type) > Type > Type) ': r) a > Sem r a #
failToError :: forall e (r :: [(Type > Type) > Type > Type]) a. Member (Error e :: (Type > Type) > Type > Type) r => (String > e) > Sem ((Fail :: (Type > Type) > Type > Type) ': r) a > Sem r a #
runFail :: forall (r :: [(Type > Type) > Type > Type]) a. Sem ((Fail :: (Type > Type) > Type > Type) ': r) a > Sem r (Either String a) #
Run a Fail
effect purely.
runInputSem :: forall i (r :: EffectRow) a. Sem r i > Sem ((Input i :: (Type > Type) > Type > Type) ': r) a > Sem r a #
Runs an Input
effect by evaluating a monadic action for each request.
runInputList :: forall i (r :: [(Type > Type) > Type > Type]) a. [i] > Sem ((Input (Maybe i) :: (Type > Type) > Type > Type) ': r) a > Sem r a #
runInputConst :: forall i (r :: [(Type > Type) > Type > Type]) a. i > Sem ((Input i :: (Type > Type) > Type > Type) ': r) a > Sem r a #
Run an Input
effect by always giving back the same value.
inputs :: forall i j (r :: [(Type > Type) > Type > Type]). Member (Input i :: (Type > Type) > Type > Type) r => (i > j) > Sem r j #
Apply a function to an input, cf. asks
input :: forall i (r :: [Effect]). MemberWithError (Input i :: (Type > Type) > Type > Type) r => Sem r i #
data Input (i :: k) (m :: k1) (a :: k) #
An effect which can provide input to an application. Useful for dealing with streaming input.
Instances
type DefiningModule (Input :: k1 > k2 > k1 > Type)  
Defined in Polysemy.Input 
runOutputSem :: forall o (r :: EffectRow) a. (o > Sem r ()) > Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r a #
Runs an Output
effect by running a monadic action for each of its
values.
runOutputBatched :: forall o (r :: [(Type > Type) > Type > Type]) a. Member (Output [o] :: (Type > Type) > Type > Type) r => Int > Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r a #
ignoreOutput :: forall o (r :: [(Type > Type) > Type > Type]) a. Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r a #
Run an Output
effect by ignoring it.
Since: polysemy1.0.0.0
outputToIOMonoidAssocR :: forall o m (r :: [(Type > Type) > Type > Type]) a. (Monoid m, Member (Embed IO) r) => (o > m) > Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r (m, a) #
Like outputToIOMonoid
, but rightassociates uses of <>
.
This asymptotically improves performance if the time complexity of <>
for
the Monoid
depends only on the size of the first argument.
You should always use this instead of outputToIOMonoid
if the monoid
is a list, such as String
.
Beware: As this uses an IORef
internally,
all other effects will have local
state semantics in regards to Output
effects
interpreted this way.
For example, throw
and catch
will
never revert output
s, even if runError
is used
after outputToIOMonoidAssocR
.
Since: polysemy1.2.0.0
outputToIOMonoid :: forall o m (r :: [(Type > Type) > Type > Type]) a. (Monoid m, Member (Embed IO) r) => (o > m) > Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r (m, a) #
Run an Output
effect in terms of atomic operations
in IO
.
Internally, this simply creates a new IORef
, passes it to
runOutputMonoidIORef
, and then returns the result and the final value
of the IORef
.
Beware: As this uses an IORef
internally,
all other effects will have local
state semantics in regards to Output
effects
interpreted this way.
For example, throw
and catch
will
never revert output
s, even if runError
is used
after outputToIOMonoid
.
Since: polysemy1.2.0.0
runOutputMonoidTVar :: forall o m (r :: [(Type > Type) > Type > Type]) a. (Monoid m, Member (Embed IO) r) => TVar m > (o > m) > Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r a #
runOutputMonoidIORef :: forall o m (r :: [(Type > Type) > Type > Type]) a. (Monoid m, Member (Embed IO) r) => IORef m > (o > m) > Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r a #
runLazyOutputMonoidAssocR :: forall o m (r :: [(Type > Type) > Type > Type]) a. Monoid m => (o > m) > Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r (m, a) #
Like runLazyOutputMonoid
, but rightassociates uses of <>
.
This asymptotically improves performance if the time complexity of <>
for
the Monoid
depends only on the size of the first argument.
You should always use this instead of runLazyOutputMonoid
if the monoid
is a list, such as String
.
Warning: This inherits the nasty space leak issue of
WriterT
! Don't use this if you don't have to.
Since: polysemy1.3.0.0
runOutputMonoidAssocR :: forall o m (r :: [(Type > Type) > Type > Type]) a. Monoid m => (o > m) > Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r (m, a) #
Like runOutputMonoid
, but rightassociates uses of <>
.
This asymptotically improves performance if the time complexity of <>
for
the Monoid
depends only on the size of the first argument.
You should always use this instead of runOutputMonoid
if the monoid
is a list, such as String
.
Since: polysemy1.1.0.0
runLazyOutputMonoid :: forall o m (r :: [(Type > Type) > Type > Type]) a. Monoid m => (o > m) > Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r (m, a) #
runOutputMonoid :: forall o m (r :: [(Type > Type) > Type > Type]) a. Monoid m => (o > m) > Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r (m, a) #
Run an Output
effect by transforming it into a monoid.
Since: polysemy1.0.0.0
runLazyOutputList :: forall o (r :: [(Type > Type) > Type > Type]) a. Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r ([o], a) #
runOutputList :: forall o (r :: [(Type > Type) > Type > Type]) a. Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r ([o], a) #
Run an Output
effect by transforming it into a list of its values.
Since: polysemy1.0.0.0
output :: forall o (r :: [Effect]). MemberWithError (Output o :: (Type > Type) > Type > Type) r => o > Sem r () #
An effect capable of sending messages. Useful for streaming output and for logging.
Instances
type DefiningModule (Output :: Type > k > Type > Type)  
Defined in Polysemy.Output 
inputToReader :: forall i (r :: [(Type > Type) > Type > Type]) a. Member (Reader i) r => Sem ((Input i :: (Type > Type) > Type > Type) ': r) a > Sem r a #
runReader :: forall i (r :: [(Type > Type) > Type > Type]) a. i > Sem (Reader i ': r) a > Sem r a #
Run a Reader
effect with a constant value.
asks :: forall i j (r :: [(Type > Type) > Type > Type]). Member (Reader i) r => (i > j) > Sem r j #
local :: forall i (r :: [Effect]) a. MemberWithError (Reader i) r => (i > i) > Sem r a > Sem r a #
data Reader i (m :: Type > Type) a #
An effect corresponding to ReaderT
.
Instances
type DefiningModule Reader  
Defined in Polysemy.Reader 
resourceToIO :: forall (r :: [(Type > Type) > Type > Type]) a. Member (Embed IO) r => Sem (Resource ': r) a > Sem r a #
A more flexible  though less safe  version of resourceToIOFinal
This function is capable of running Resource
effects anywhere within an
effect stack, without relying on an explicit function to lower it into IO
.
Notably, this means that State
effects will be consistent
in the presence of Resource
.
ResourceToIO' is safe whenever you're concerned about exceptions thrown
by effects _already handled_ in your effect stack, or in IO
code run
directly inside of bracket
. It is not safe against exceptions thrown
explicitly at the main thread. If this is not safe enough for your usecase,
use resourceToIOFinal
instead.
This function creates a thread, and so should be compiled with threaded
.
Since: polysemy1.0.0.0
runResource :: forall (r :: [(Type > Type) > Type > Type]) a. Sem (Resource ': r) a > Sem r a #
Run a Resource
effect purely.
Since: polysemy1.0.0.0
resourceToIOFinal :: forall (r :: [(Type > Type) > Type > Type]) a. Member (Final IO) r => Sem (Resource ': r) a > Sem r a #
Run a Resource
effect in terms of bracket
through final IO
Beware: Effects that aren't interpreted in terms of IO
will have local state semantics in regards to Resource
effects
interpreted this way. See Final
.
Notably, unlike resourceToIO
, this is not consistent with
State
unless runStateInIORef
is used.
State that seems like it should be threaded globally throughout bracket
s
will not be.
Use resourceToIO
instead if you need to run
pure, stateful interpreters after the interpreter for Resource
.
(Pure interpreters are interpreters that aren't expressed in terms of
another effect or monad; for example, runState
.)
Since: polysemy1.2.0.0
:: forall (r :: [(Type > Type) > Type > Type]) a b. Member Resource r  
=> Sem r a  computation to run first 
> Sem r b  computation to run afterward if an exception was raised 
> Sem r a 
Like bracketOnError
, but for the simple case of one computation to run
afterward.
Since: polysemy0.4.0.0
:: forall (r :: [(Type > Type) > Type > Type]) a b. Member Resource r  
=> Sem r a  computation to run first 
> Sem r b  computation to run afterward (even if an exception was raised) 
> Sem r a 
Like bracket
, but for the simple case of one computation to run
afterward.
Since: polysemy0.4.0.0
bracketOnError :: forall (r :: [Effect]) a c b. MemberWithError Resource r => Sem r a > (a > Sem r c) > (a > Sem r b) > Sem r b #
bracket :: forall (r :: [Effect]) a c b. MemberWithError Resource r => Sem r a > (a > Sem r c) > (a > Sem r b) > Sem r b #
data Resource (m :: Type > Type) a #
An effect capable of providing bracket
semantics. Interpreters for this
will successfully run the deallocation action even in the presence of other
shortcircuiting effects.
Instances
type DefiningModule Resource  
Defined in Polysemy.Resource 
hoistStateIntoStateT :: forall s (r :: [(Type > Type) > Type > Type]) a. Sem ((State s :: (Type > Type) > Type > Type) ': r) a > StateT s (Sem r) a #
stateToST :: forall s st (r :: [(Type > Type) > Type > Type]) a. Member (Embed (ST st)) r => s > Sem ((State s :: (Type > Type) > Type > Type) ': r) a > Sem r (s, a) #
Run an State
effect in terms of operations
in ST
.
Internally, this simply creates a new STRef
, passes it to
runStateSTRef
, and then returns the result and the final value
of the STRef
.
Beware: As this uses an STRef
internally,
all other effects will have local
state semantics in regards to State
effects
interpreted this way.
For example, throw
and catch
will
never revert put
s, even if runError
is used
after stateToST
.
When not using the plugin, one must introduce the existential st
type to
stateToST
, so that the resulting type after runM
can be resolved into
forall st. ST st (s, a)
for use with runST
. Doing so requires
XScopedTypeVariables
.
stResult :: forall s a. (s, a) stResult = runST ( (runM $ stateToST @_ @st undefined $ pure undefined) :: forall st. ST st (s, a) )
Since: polysemy1.3.0.0
runStateSTRef :: forall s st (r :: [(Type > Type) > Type > Type]) a. Member (Embed (ST st)) r => STRef st s > Sem ((State s :: (Type > Type) > Type > Type) ': r) a > Sem r a #
stateToIO :: forall s (r :: [(Type > Type) > Type > Type]) a. Member (Embed IO) r => s > Sem ((State s :: (Type > Type) > Type > Type) ': r) a > Sem r (s, a) #
Run an State
effect in terms of operations
in IO
.
Internally, this simply creates a new IORef
, passes it to
runStateIORef
, and then returns the result and the final value
of the IORef
.
Note: This is not safe in a concurrent setting, as modify
isn't atomic.
If you need operations over the state to be atomic,
use atomicStateToIO
instead.
Beware: As this uses an IORef
internally,
all other effects will have local
state semantics in regards to State
effects
interpreted this way.
For example, throw
and catch
will
never revert put
s, even if runError
is used
after stateToIO
.
Since: polysemy1.2.0.0
runStateIORef :: forall s (r :: [(Type > Type) > Type > Type]) a. Member (Embed IO) r => IORef s > Sem ((State s :: (Type > Type) > Type > Type) ': r) a > Sem r a #
Run a State
effect by transforming it into operations over an IORef
.
Note: This is not safe in a concurrent setting, as modify
isn't atomic.
If you need operations over the state to be atomic,
use runAtomicStateIORef
or
runAtomicStateTVar
instead.
Since: polysemy1.0.0.0
execLazyState :: forall s (r :: [(Type > Type) > Type > Type]) a. s > Sem ((State s :: (Type > Type) > Type > Type) ': r) a > Sem r s #
Run a State
effect with local state, lazily.
Since: polysemy1.2.3.1
evalLazyState :: forall s (r :: [(Type > Type) > Type > Type]) a. s > Sem ((State s :: (Type > Type) > Type > Type) ': r) a > Sem r a #
Run a State
effect with local state, lazily.
Since: polysemy1.0.0.0
runLazyState :: forall s (r :: [(Type > Type) > Type > Type]) a. s > Sem ((State s :: (Type > Type) > Type > Type) ': r) a > Sem r (s, a) #
Run a State
effect with local state, lazily.
execState :: forall s (r :: [(Type > Type) > Type > Type]) a. s > Sem ((State s :: (Type > Type) > Type > Type) ': r) a > Sem r s #
Run a State
effect with local state.
Since: polysemy1.2.3.1
evalState :: forall s (r :: [(Type > Type) > Type > Type]) a. s > Sem ((State s :: (Type > Type) > Type > Type) ': r) a > Sem r a #
Run a State
effect with local state.
Since: polysemy1.0.0.0
runState :: forall s (r :: [(Type > Type) > Type > Type]) a. s > Sem ((State s :: (Type > Type) > Type > Type) ': r) a > Sem r (s, a) #
Run a State
effect with local state.
modify' :: forall s (r :: [(Type > Type) > Type > Type]). Member (State s :: (Type > Type) > Type > Type) r => (s > s) > Sem r () #
A variant of modify
in which the computation is strict in the
new state.
modify :: forall s (r :: [(Type > Type) > Type > Type]). Member (State s :: (Type > Type) > Type > Type) r => (s > s) > Sem r () #
gets :: forall s a (r :: [(Type > Type) > Type > Type]). Member (State s :: (Type > Type) > Type > Type) r => (s > a) > Sem r a #
put :: forall s (r :: [Effect]). MemberWithError (State s :: (Type > Type) > Type > Type) r => s > Sem r () #
get :: forall s (r :: [Effect]). MemberWithError (State s :: (Type > Type) > Type > Type) r => Sem r s #
An effect for providing statefulness. Note that unlike mtl's
StateT
, there is no restriction that the State
effect corresponds necessarily to local state. It could could just as well
be interrpeted in terms of HTTP requests or database access.
Interpreters which require statefulness can reinterpret
themselves in terms of State
, and subsequently call runState
.
Instances
type DefiningModule (State :: Type > k > Type > Type)  
Defined in Polysemy.State 
retag :: forall {k1} {k2} (k3 :: k1) (k4 :: k2) (e :: (Type > Type) > Type > Type) (r :: [(Type > Type) > Type > Type]) a. Member (Tagged k4 e) r => Sem (Tagged k3 e ': r) a > Sem r a #
untag :: forall {k1} (k2 :: k1) (e :: (Type > Type) > Type > Type) (r :: [(Type > Type) > Type > Type]) a. Sem (Tagged k2 e ': r) a > Sem (e ': r) a #
Run a
effect through reinterpreting it to Tagged
k ee
tagged :: forall {k1} (k2 :: k1) (e :: Effect) (r :: [Effect]) a. Sem (e ': r) a > Sem (Tagged k2 e ': r) a #
A reinterpreting version of tag
.
tag :: forall {k1} (k2 :: k1) (e :: (Type > Type) > Type > Type) (r :: [(Type > Type) > Type > Type]) a. Member (Tagged k2 e) r => Sem (e ': r) a > Sem r a #
Tag uses of an effect, effectively gaining access to the tagged effect locally.
This may be used to create tagged
variants of regular actions.
For example:
taggedLocal :: forall k i r a .Member
(Tagged
k (Reader
i)) r => (i > i) >Sem
r a >Sem
r a taggedLocal f m =tag
k
(Reader
i) $local
@i f (raise
m)
data Tagged (k3 :: k) (e :: k1 > k2 > Type) (m :: k1) (a :: k2) #
An effect for annotating effects and disambiguating identical effects.
writerToIOAssocRFinal :: forall o (r :: [(Type > Type) > Type > Type]) a. (Monoid o, Member (Final IO) r) => Sem (Writer o ': r) a > Sem r (o, a) #
Like writerToIOFinal
. but rightassociates uses of <>
.
This asymptotically improves performance if the time complexity of <>
for the Monoid
depends only on the size of the first argument.
You should always use this instead of writerToIOFinal
if the monoid
is a list, such as String
.
Beware: Effects that aren't interpreted in terms of IO
will have local state semantics in regards to Writer
effects
interpreted this way. See Final
.
Since: polysemy1.2.0.0
writerToIOFinal :: forall o (r :: [(Type > Type) > Type > Type]) a. (Monoid o, Member (Final IO) r) => Sem (Writer o ': r) a > Sem r (o, a) #
Run a Writer
effect by transforming it into atomic operations
through final IO
.
Internally, this simply creates a new TVar
, passes it to
runWriterTVar
, and then returns the result and the final value
of the TVar
.
Beware: Effects that aren't interpreted in terms of IO
will have local state semantics in regards to Writer
effects
interpreted this way. See Final
.
Since: polysemy1.2.0.0
runWriterTVar :: forall o (r :: [(Type > Type) > Type > Type]) a. (Monoid o, Member (Final IO) r) => TVar o > Sem (Writer o ': r) a > Sem r a #
runLazyWriterAssocR :: forall o (r :: [(Type > Type) > Type > Type]) a. Monoid o => Sem (Writer o ': r) a > Sem r (o, a) #
Like runLazyWriter
, but rightassociates uses of <>
.
This asymptotically improves performance if the time complexity of <>
for the Monoid
depends only on the size of the first argument.
You should always use this instead of runLazyWriter
if the monoid
is a list, such as String
.
Warning: This inherits the nasty space leak issue of
WriterT
! Don't use this if you don't have to.
Since: polysemy1.3.0.0
runWriterAssocR :: forall o (r :: [(Type > Type) > Type > Type]) a. Monoid o => Sem (Writer o ': r) a > Sem r (o, a) #
runLazyWriter :: forall o (r :: [(Type > Type) > Type > Type]) a. Monoid o => Sem (Writer o ': r) a > Sem r (o, a) #
runWriter :: forall o (r :: [(Type > Type) > Type > Type]) a. Monoid o => Sem (Writer o ': r) a > Sem r (o, a) #
outputToWriter :: forall o (r :: [(Type > Type) > Type > Type]) a. Member (Writer o) r => Sem ((Output o :: (Type > Type) > Type > Type) ': r) a > Sem r a #
censor :: forall o (r :: [(Type > Type) > Type > Type]) a. Member (Writer o) r => (o > o) > Sem r a > Sem r a #
Since: polysemy0.7.0.0
writerToEndoWriter :: forall o (r :: [(Type > Type) > Type > Type]) a. (Monoid o, Member (Writer (Endo o)) r) => Sem (Writer o ': r) a > Sem r a #
data Writer o (m :: Type > Type) a #
An effect capable of emitting and intercepting messages.
Instances
type DefiningModule Writer  
Defined in Polysemy.Internal.Writer 