


Description 
Utilities related to Monad and Applicative classes
Mostly for backwards compatability.


Synopsis 

class Functor f => Applicative f where  pure :: a > f a  (<*>) :: f (a > b) > f a > f b  (*>) :: f a > f b > f b  (<*) :: f a > f b > f a 
  (<$>) :: Functor f => (a > b) > f a > f b   class Monad m => MonadFix m where  mfix :: (a > m a) > m a 
  class Monad m => MonadIO m where    liftIO1 :: MonadIO m => (a > IO b) > a > m b   liftIO2 :: MonadIO m => (a > b > IO c) > a > b > m c   liftIO3 :: MonadIO m => (a > b > c > IO d) > a > b > c > m d   liftIO4 :: MonadIO m => (a > b > c > d > IO e) > a > b > c > d > m e   zipWith3M :: Monad m => (a > b > c > m d) > [a] > [b] > [c] > m [d]   mapAndUnzipM :: Monad m => (a > m (b, c)) > [a] > m ([b], [c])   mapAndUnzip3M :: Monad m => (a > m (b, c, d)) > [a] > m ([b], [c], [d])   mapAndUnzip4M :: Monad m => (a > m (b, c, d, e)) > [a] > m ([b], [c], [d], [e])   mapAccumLM :: Monad m => (acc > x > m (acc, y)) > acc > [x] > m (acc, [y])   mapSndM :: Monad m => (b > m c) > [(a, b)] > m [(a, c)]   concatMapM :: Monad m => (a > m [b]) > [a] > m [b]   mapMaybeM :: Monad m => (a > m (Maybe b)) > [a] > m [b]   anyM :: Monad m => (a > m Bool) > [a] > m Bool   allM :: Monad m => (a > m Bool) > [a] > m Bool   foldlM :: Monad m => (a > b > m a) > a > [b] > m a   foldlM_ :: Monad m => (a > b > m a) > a > [b] > m ()   foldrM :: Monad m => (b > a > m a) > a > [b] > m a   maybeMapM :: Monad m => (a > m b) > Maybe a > m (Maybe b) 


Documentation 


A functor with application.
Instances should satisfy the following laws:
 identity

pure id <*> v = v
 composition

pure (.) <*> u <*> v <*> w = u <*> (v <*> w)
 homomorphism

pure f <*> pure x = pure (f x)
 interchange

u <*> pure y = pure ($ y) <*> u
 ignore left value

u *> v = pure (const id) <*> u <*> v
 ignore right value

u <* v = pure const <*> u <*> v
The Functor instance should satisfy
fmap f x = pure f <*> x
If f is also a Monad, define pure = return and (<*>) = ap.
Minimal complete definition: pure and <*>.
  Methods   Lift a value.
  (<*>) :: f (a > b) > f a > f b  Source 
 Sequential application.
  (*>) :: f a > f b > f b  Source 
 Sequence actions, discarding the value of the first argument.
  (<*) :: f a > f b > f a  Source 
 Sequence actions, discarding the value of the second argument.

  Instances  



An infix synonym for fmap.



Monads having fixed points with a 'knottying' semantics.
Instances of MonadFix should satisfy the following laws:
 purity

mfix (return . h) = return (fix h)
 left shrinking (or tightening)

mfix (\x > a >>= \y > f x y) = a >>= \y > mfix (\x > f x y)
 sliding

mfix (Control.Monad.liftM h . f) = Control.Monad.liftM h (mfix (f . h)),
for strict h.
 nesting

mfix (\x > mfix (\y > f x y)) = mfix (\x > f x x)
This class is used in the translation of the recursive do notation
supported by GHC and Hugs.
  Methods  mfix :: (a > m a) > m a  Source 
 The fixed point of a monadic computation.
mfix f executes the action f only once, with the eventual
output fed back as the input. Hence f should not be strict,
for then mfix f would diverge.

  Instances  



 Methods    Instances  



Lift an IO operation with 1 argument into another monad



Lift an IO operation with 2 arguments into another monad



Lift an IO operation with 3 arguments into another monad


liftIO4 :: MonadIO m => (a > b > c > d > IO e) > a > b > c > d > m e  Source 

Lift an IO operation with 4 arguments into another monad


zipWith3M :: Monad m => (a > b > c > m d) > [a] > [b] > [c] > m [d]  Source 


mapAndUnzipM :: Monad m => (a > m (b, c)) > [a] > m ([b], [c])  Source 

The mapAndUnzipM function maps its first argument over a list, returning
the result as a pair of lists. This function is mainly used with complicated
data structures or a statetransforming monad.


mapAndUnzip3M :: Monad m => (a > m (b, c, d)) > [a] > m ([b], [c], [d])  Source 

mapAndUnzipM for triples


mapAndUnzip4M :: Monad m => (a > m (b, c, d, e)) > [a] > m ([b], [c], [d], [e])  Source 



:: Monad m   => acc > x > m (acc, y)  initial state
 > acc  inputs
 > [x]  final state, outputs
 > m (acc, [y])   Monadic version of mapAccumL



mapSndM :: Monad m => (b > m c) > [(a, b)] > m [(a, c)]  Source 

Monadic version of mapSnd


concatMapM :: Monad m => (a > m [b]) > [a] > m [b]  Source 

Monadic version of concatMap



Monadic version of mapMaybe



Monadic version of any, aborts the computation at the first True value



Monad version of all, aborts the computation at the first False value


foldlM :: Monad m => (a > b > m a) > a > [b] > m a  Source 

Monadic version of foldl



Monadic version of foldl that discards its result


foldrM :: Monad m => (b > a > m a) > a > [b] > m a  Source 

Monadic version of foldr



Monadic version of fmap specialised for Maybe


Produced by Haddock version 2.6.0 