Mini.Transformers.ReaderT

Extension of a monad with a read-only environment

Type

data ReaderT r m a

A monad with read-only type r, inner monad m, and return type a

Instances

MonadTrans (ReaderT r)

Defined in Mini.Transformers.ReaderT

Methods

lift :: Monad m => m a -> ReaderT r m a

(Monad m, Alternative m) => Alternative (ReaderT r m)

Defined in Mini.Transformers.ReaderT

Methods

empty :: ReaderT r m a

(<|>) :: ReaderT r m a -> ReaderT r m a -> ReaderT r m a

some :: ReaderT r m a -> ReaderT r m [a]

many :: ReaderT r m a -> ReaderT r m [a]

Monad m => Applicative (ReaderT r m)

Defined in Mini.Transformers.ReaderT

Methods

pure :: a -> ReaderT r m a

(<*>) :: ReaderT r m (a -> b) -> ReaderT r m a -> ReaderT r m b

liftA2 :: (a -> b -> c) -> ReaderT r m a -> ReaderT r m b -> ReaderT r m c

(*>) :: ReaderT r m a -> ReaderT r m b -> ReaderT r m b

(<*) :: ReaderT r m a -> ReaderT r m b -> ReaderT r m a

Monad m => Functor (ReaderT r m)

Defined in Mini.Transformers.ReaderT

Methods

fmap :: (a -> b) -> ReaderT r m a -> ReaderT r m b

(<$) :: a -> ReaderT r m b -> ReaderT r m a

Monad m => Monad (ReaderT r m)

Defined in Mini.Transformers.ReaderT

Methods

(>>=) :: ReaderT r m a -> (a -> ReaderT r m b) -> ReaderT r m b

(>>) :: ReaderT r m a -> ReaderT r m b -> ReaderT r m b

return :: a -> ReaderT r m a

Reading

ask :: Monad m => ReaderT r m r

Fetch the read-only value

foo = do
  r <- ask
  bar r

Runners

runReaderT :: ReaderT r m a -> r -> m a

Unwrap a ReaderT given a read-only value