Control.Monad.Stream

This Haskell library provides an implementation of the MonadPlus type class that enumerates results of a non-deterministic computation by interleaving subcomputations in a way that has usually much better memory performance than other strategies with the same termination properties.

By using supensions in strategic positions, the user can ensure that the search does not diverge if there are remaining non-deterministic results.

More information is available on the author's website: http://okmij.org/ftp/Computation/monads.html#fair-bt-stream

Warning: Stream is only a monad when the results of observeAll are interpreted as a multiset, i.e., a valid transformation according to the monad laws may change the order of the results.

Documentation

data StreamT m a

Results of non-deterministic computations of type StreamT m a can be enumerated efficiently.

Instances

MonadTrans StreamT

Defined in Control.Monad.Stream

Methods

lift :: Monad m => m a -> StreamT m a

MonadState s m => MonadState s (StreamT m)

Defined in Control.Monad.Stream

Methods

get :: StreamT m s

put :: s -> StreamT m ()

state :: (s -> (a, s)) -> StreamT m a

MonadReader r m => MonadReader r (StreamT m)

Defined in Control.Monad.Stream

Methods

ask :: StreamT m r

local :: (r -> r) -> StreamT m a -> StreamT m a

reader :: (r -> a) -> StreamT m a

Monad m => Monad (StreamT m)

Defined in Control.Monad.Stream

Methods

(>>=) :: StreamT m a -> (a -> StreamT m b) -> StreamT m b

(>>) :: StreamT m a -> StreamT m b -> StreamT m b

return :: a -> StreamT m a

Monad m => Functor (StreamT m)

Defined in Control.Monad.Stream

Methods

fmap :: (a -> b) -> StreamT m a -> StreamT m b

(<$) :: a -> StreamT m b -> StreamT m a

Monad m => MonadFail (StreamT m)

Defined in Control.Monad.Stream

Methods

fail :: String -> StreamT m a

Monad m => Applicative (StreamT m)

Defined in Control.Monad.Stream

Methods

pure :: a -> StreamT m a

(<*>) :: StreamT m (a -> b) -> StreamT m a -> StreamT m b

liftA2 :: (a -> b -> c) -> StreamT m a -> StreamT m b -> StreamT m c

(*>) :: StreamT m a -> StreamT m b -> StreamT m b

(<*) :: StreamT m a -> StreamT m b -> StreamT m a

(Monad m, Foldable m) => Foldable (StreamT m)

Defined in Control.Monad.Stream

Methods

fold :: Monoid m0 => StreamT m m0 -> m0

foldMap :: Monoid m0 => (a -> m0) -> StreamT m a -> m0

foldMap' :: Monoid m0 => (a -> m0) -> StreamT m a -> m0

foldr :: (a -> b -> b) -> b -> StreamT m a -> b

foldr' :: (a -> b -> b) -> b -> StreamT m a -> b

foldl :: (b -> a -> b) -> b -> StreamT m a -> b

foldl' :: (b -> a -> b) -> b -> StreamT m a -> b

foldr1 :: (a -> a -> a) -> StreamT m a -> a

foldl1 :: (a -> a -> a) -> StreamT m a -> a

toList :: StreamT m a -> [a]

null :: StreamT m a -> Bool

length :: StreamT m a -> Int

elem :: Eq a => a -> StreamT m a -> Bool

maximum :: Ord a => StreamT m a -> a

minimum :: Ord a => StreamT m a -> a

sum :: Num a => StreamT m a -> a

product :: Num a => StreamT m a -> a

(Monad m, Traversable m) => Traversable (StreamT m)

Defined in Control.Monad.Stream

Methods

traverse :: Applicative f => (a -> f b) -> StreamT m a -> f (StreamT m b)

sequenceA :: Applicative f => StreamT m (f a) -> f (StreamT m a)

mapM :: Monad m0 => (a -> m0 b) -> StreamT m a -> m0 (StreamT m b)

sequence :: Monad m0 => StreamT m (m0 a) -> m0 (StreamT m a)

MonadIO m => MonadIO (StreamT m)

Defined in Control.Monad.Stream

Methods

liftIO :: IO a -> StreamT m a

Monad m => Alternative (StreamT m)

Defined in Control.Monad.Stream

Methods

empty :: StreamT m a

(<|>) :: StreamT m a -> StreamT m a -> StreamT m a

some :: StreamT m a -> StreamT m [a]

many :: StreamT m a -> StreamT m [a]

Monad m => MonadPlus (StreamT m)

Defined in Control.Monad.Stream

Methods

mzero :: StreamT m a

mplus :: StreamT m a -> StreamT m a -> StreamT m a

Monad m => MonadLogic (StreamT m)

Defined in Control.Monad.Stream

Methods

msplit :: StreamT m a -> StreamT m (Maybe (a, StreamT m a))

interleave :: StreamT m a -> StreamT m a -> StreamT m a

(>>-) :: StreamT m a -> (a -> StreamT m b) -> StreamT m b

ifte :: StreamT m a -> (a -> StreamT m b) -> StreamT m b -> StreamT m b

once :: StreamT m a -> StreamT m a

lnot :: StreamT m a -> StreamT m ()

Monad m => Semigroup (StreamT m a)

Defined in Control.Monad.Stream

Methods

(<>) :: StreamT m a -> StreamT m a -> StreamT m a

sconcat :: NonEmpty (StreamT m a) -> StreamT m a

stimes :: Integral b => b -> StreamT m a -> StreamT m a

Monad m => Monoid (StreamT m a)

Defined in Control.Monad.Stream

Methods

mempty :: StreamT m a

mappend :: StreamT m a -> StreamT m a -> StreamT m a

mconcat :: [StreamT m a] -> StreamT m a

type Stream = StreamT Identity

suspended :: Monad m => StreamT m a -> StreamT m a

Suspensions can be used to ensure fairness.

runStream :: Stream a -> [a]

Deprecated: use observeAll

The function runStream enumerates the results of a non-deterministic computation.

observe :: Stream a -> a

observeT :: MonadFail m => StreamT m a -> m a

observeAll :: Stream a -> [a]

observeAllT :: Monad m => StreamT m a -> m [a]

observeMany :: Int -> Stream a -> [a]

observeManyT :: Monad m => Int -> StreamT m a -> m [a]

module Control.Monad.Logic.Class