transformers-0.5.5.0: Concrete functor and monad transformers

Control.Applicative.Lift

Description

Adding a new kind of pure computation to an applicative functor.

Synopsis

# Lifting an applicative

data Lift f a Source #

Applicative functor formed by adding pure computations to a given applicative functor.

Constructors

 Pure a Other (f a)
Instances
 Functor f => Functor (Lift f) Source # Instance detailsMethodsfmap :: (a -> b) -> Lift f a -> Lift f b #(<\$) :: a -> Lift f b -> Lift f a # Applicative f => Applicative (Lift f) Source # A combination is Pure only if both parts are. Instance detailsMethodspure :: a -> Lift f a #(<*>) :: Lift f (a -> b) -> Lift f a -> Lift f b #liftA2 :: (a -> b -> c) -> Lift f a -> Lift f b -> Lift f c #(*>) :: Lift f a -> Lift f b -> Lift f b #(<*) :: Lift f a -> Lift f b -> Lift f a # Foldable f => Foldable (Lift f) Source # Instance detailsMethodsfold :: Monoid m => Lift f m -> m #foldMap :: Monoid m => (a -> m) -> Lift f a -> m #foldr :: (a -> b -> b) -> b -> Lift f a -> b #foldr' :: (a -> b -> b) -> b -> Lift f a -> b #foldl :: (b -> a -> b) -> b -> Lift f a -> b #foldl' :: (b -> a -> b) -> b -> Lift f a -> b #foldr1 :: (a -> a -> a) -> Lift f a -> a #foldl1 :: (a -> a -> a) -> Lift f a -> a #toList :: Lift f a -> [a] #null :: Lift f a -> Bool #length :: Lift f a -> Int #elem :: Eq a => a -> Lift f a -> Bool #maximum :: Ord a => Lift f a -> a #minimum :: Ord a => Lift f a -> a #sum :: Num a => Lift f a -> a #product :: Num a => Lift f a -> a # Traversable f => Traversable (Lift f) Source # Instance detailsMethodstraverse :: Applicative f0 => (a -> f0 b) -> Lift f a -> f0 (Lift f b) #sequenceA :: Applicative f0 => Lift f (f0 a) -> f0 (Lift f a) #mapM :: Monad m => (a -> m b) -> Lift f a -> m (Lift f b) #sequence :: Monad m => Lift f (m a) -> m (Lift f a) # Eq1 f => Eq1 (Lift f) Source # Instance detailsMethodsliftEq :: (a -> b -> Bool) -> Lift f a -> Lift f b -> Bool # Ord1 f => Ord1 (Lift f) Source # Instance detailsMethodsliftCompare :: (a -> b -> Ordering) -> Lift f a -> Lift f b -> Ordering # Read1 f => Read1 (Lift f) Source # Instance detailsMethodsliftReadsPrec :: (Int -> ReadS a) -> ReadS [a] -> Int -> ReadS (Lift f a) #liftReadList :: (Int -> ReadS a) -> ReadS [a] -> ReadS [Lift f a] #liftReadPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec (Lift f a) #liftReadListPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec [Lift f a] # Show1 f => Show1 (Lift f) Source # Instance detailsMethodsliftShowsPrec :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> Int -> Lift f a -> ShowS #liftShowList :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> [Lift f a] -> ShowS # Alternative f => Alternative (Lift f) Source # A combination is Pure only either part is. Instance detailsMethodsempty :: Lift f a #(<|>) :: Lift f a -> Lift f a -> Lift f a #some :: Lift f a -> Lift f [a] #many :: Lift f a -> Lift f [a] # (Eq1 f, Eq a) => Eq (Lift f a) Source # Instance detailsMethods(==) :: Lift f a -> Lift f a -> Bool #(/=) :: Lift f a -> Lift f a -> Bool # (Ord1 f, Ord a) => Ord (Lift f a) Source # Instance detailsMethodscompare :: Lift f a -> Lift f a -> Ordering #(<) :: Lift f a -> Lift f a -> Bool #(<=) :: Lift f a -> Lift f a -> Bool #(>) :: Lift f a -> Lift f a -> Bool #(>=) :: Lift f a -> Lift f a -> Bool #max :: Lift f a -> Lift f a -> Lift f a #min :: Lift f a -> Lift f a -> Lift f a # (Read1 f, Read a) => Read (Lift f a) Source # Instance detailsMethodsreadsPrec :: Int -> ReadS (Lift f a) #readList :: ReadS [Lift f a] #readPrec :: ReadPrec (Lift f a) #readListPrec :: ReadPrec [Lift f a] # (Show1 f, Show a) => Show (Lift f a) Source # Instance detailsMethodsshowsPrec :: Int -> Lift f a -> ShowS #show :: Lift f a -> String #showList :: [Lift f a] -> ShowS #

unLift :: Applicative f => Lift f a -> f a Source #

Projection to the other functor.

mapLift :: (f a -> g a) -> Lift f a -> Lift g a Source #

Apply a transformation to the other computation.

elimLift :: (a -> r) -> (f a -> r) -> Lift f a -> r Source #

Eliminator for Lift.

• elimLift f g . pure = f
• elimLift f g . Other = g

# Collecting errors

type Errors e = Lift (Constant e) Source #

An applicative functor that collects a monoid (e.g. lists) of errors. A sequence of computations fails if any of its components do, but unlike monads made with ExceptT from Control.Monad.Trans.Except, these computations continue after an error, collecting all the errors.

• pure f <*> pure x = pure (f x)
• pure f <*> failure e = failure e
• failure e <*> pure x = failure e
• failure e1 <*> failure e2 = failure (e1 <> e2)

runErrors :: Errors e a -> Either e a Source #

Extractor for computations with accumulating errors.

• runErrors (pure x) = Right x
• runErrors (failure e) = Left e

failure :: e -> Errors e a Source #

Report an error.

eitherToErrors :: Either e a -> Errors e a Source #

Convert from Either to Errors (inverse of runErrors).