|Portability||non-portable (GHC Extensions)|
This module provides the implementation of the
STT type for those
occasions where it's needed in order to implement new liftings through
operations in other monads.
Warning! This monad transformer should not be used with monads that can contain multiple answers, like the list monad. The reason is that the will be duplicated across the different answers and this cause Bad Things to happen (such as loss of referential transparency). Safe monads include the monads State, Reader, Writer, Maybe and combinations of their corresponding monad transformers.
STT is the monad transformer providing polymorphic updateable references
|MonadError e m => MonadError e (STT s m)|
|MonadReader r m => MonadReader r (STT s m)|
|MonadState s m => MonadState s (STT s' m)|
|MonadWriter w m => MonadWriter w (STT s m)|
|MonadTrans (STT s)|
|Monad m => Monad (STT s m)|
|Functor m => Functor (STT s m)|
|MonadFix m => MonadFix (STT s m)|
|(Monad m, Functor m) => Applicative (STT s m)|