{-# LANGUAGE Trustworthy #-}{-# LANGUAGE DeriveGeneric #-}{-# LANGUAGE GeneralizedNewtypeDeriving #-}{-# LANGUAGE NoImplicitPrelude #-}------------------------------------------------------------------------------- |-- Module : Control.Applicative-- Copyright : Conor McBride and Ross Paterson 2005-- License : BSD-style (see the LICENSE file in the distribution)---- Maintainer : libraries@haskell.org-- Stability : experimental-- Portability : portable---- This module describes a structure intermediate between a functor and-- a monad (technically, a strong lax monoidal functor). Compared with-- monads, this interface lacks the full power of the binding operation-- '>>=', but---- * it has more instances.---- * it is sufficient for many uses, e.g. context-free parsing, or the-- 'Data.Traversable.Traversable' class.---- * instances can perform analysis of computations before they are-- executed, and thus produce shared optimizations.---- This interface was introduced for parsers by Niklas R&#xF6;jemo, because-- it admits more sharing than the monadic interface. The names here are-- mostly based on parsing work by Doaitse Swierstra.---- For more details, see-- <http://www.soi.city.ac.uk/~ross/papers/Applicative.html Applicative Programming with Effects>,-- by Conor McBride and Ross Paterson.moduleControl.Applicative(-- * Applicative functorsApplicative (..),-- * AlternativesAlternative (..),-- * InstancesConst (..),WrappedMonad (..),WrappedArrow (..),ZipList (..),-- * Utility functions(<$>) ,(<$) ,(<**>) ,liftA ,liftA3 ,optional ,)whereimportControl.Category hiding((.) ,id )importControl.Arrow importData.Maybe importData.Tuple importData.Eq importData.Ord importData.Foldable (Foldable (..))importData.Functor ((<$>) )importData.Functor.Const (Const (..))importGHC.Base importGHC.Generics importGHC.List (repeat ,zipWith ,drop )importGHC.Read (Read )importGHC.Show (Show )newtypeWrappedMonad m a =WrapMonad {WrappedMonad m a -> m a
unwrapMonad ::m a }deriving(Generic -- ^ @since 4.7.0.0,Generic1 -- ^ @since 4.7.0.0,Monad -- ^ @since 4.7.0.0)-- | @since 2.01instanceMonad m =>Functor (WrappedMonad m )wherefmap :: (a -> b) -> WrappedMonad m a -> WrappedMonad m b
fmap a -> b
f (WrapMonad m a
v )=m b -> WrappedMonad m b
forall (m :: * -> *) a. m a -> WrappedMonad m a
WrapMonad ((a -> b) -> m a -> m b
forall (m :: * -> *) a1 r. Monad m => (a1 -> r) -> m a1 -> m r
liftM a -> b
f m a
v )-- | @since 2.01instanceMonad m =>Applicative (WrappedMonad m )wherepure :: a -> WrappedMonad m a
pure =m a -> WrappedMonad m a
forall (m :: * -> *) a. m a -> WrappedMonad m a
WrapMonad (m a -> WrappedMonad m a) -> (a -> m a) -> a -> WrappedMonad m a
forall b c a. (b -> c) -> (a -> b) -> a -> c
. a -> m a
forall (f :: * -> *) a. Applicative f => a -> f a
pure WrapMonad m (a -> b)
f <*> :: WrappedMonad m (a -> b) -> WrappedMonad m a -> WrappedMonad m b
<*> WrapMonad m a
v =m b -> WrappedMonad m b
forall (m :: * -> *) a. m a -> WrappedMonad m a
WrapMonad (m (a -> b)
f m (a -> b) -> m a -> m b
forall (m :: * -> *) a b. Monad m => m (a -> b) -> m a -> m b
`ap` m a
v )liftA2 :: (a -> b -> c)
-> WrappedMonad m a -> WrappedMonad m b -> WrappedMonad m c
liftA2 a -> b -> c
f (WrapMonad m a
x )(WrapMonad m b
y )=m c -> WrappedMonad m c
forall (m :: * -> *) a. m a -> WrappedMonad m a
WrapMonad ((a -> b -> c) -> m a -> m b -> m c
forall (m :: * -> *) a1 a2 r.
Monad m =>
(a1 -> a2 -> r) -> m a1 -> m a2 -> m r
liftM2 a -> b -> c
f m a
x m b
y )-- | @since 2.01instanceMonadPlus m =>Alternative (WrappedMonad m )whereempty :: WrappedMonad m a
empty =m a -> WrappedMonad m a
forall (m :: * -> *) a. m a -> WrappedMonad m a
WrapMonad m a
forall (m :: * -> *) a. MonadPlus m => m a
mzero WrapMonad m a
u <|> :: WrappedMonad m a -> WrappedMonad m a -> WrappedMonad m a
<|> WrapMonad m a
v =m a -> WrappedMonad m a
forall (m :: * -> *) a. m a -> WrappedMonad m a
WrapMonad (m a
u m a -> m a -> m a
forall (m :: * -> *) a. MonadPlus m => m a -> m a -> m a
`mplus` m a
v )newtypeWrappedArrow a b c =WrapArrow {WrappedArrow a b c -> a b c
unwrapArrow ::a b c }deriving(Generic -- ^ @since 4.7.0.0,Generic1 -- ^ @since 4.7.0.0)-- | @since 2.01instanceArrow a =>Functor (WrappedArrow a b )wherefmap :: (a -> b) -> WrappedArrow a b a -> WrappedArrow a b b
fmap a -> b
f (WrapArrow a b a
a )=a b b -> WrappedArrow a b b
forall (a :: * -> * -> *) b c. a b c -> WrappedArrow a b c
WrapArrow (a b a
a a b a -> a a b -> a b b
forall k (cat :: k -> k -> *) (a :: k) (b :: k) (c :: k).
Category cat =>
cat a b -> cat b c -> cat a c
>>> (a -> b) -> a a b
forall (a :: * -> * -> *) b c. Arrow a => (b -> c) -> a b c
arr a -> b
f )-- | @since 2.01instanceArrow a =>Applicative (WrappedArrow a b )wherepure :: a -> WrappedArrow a b a
pure a
x =a b a -> WrappedArrow a b a
forall (a :: * -> * -> *) b c. a b c -> WrappedArrow a b c
WrapArrow ((b -> a) -> a b a
forall (a :: * -> * -> *) b c. Arrow a => (b -> c) -> a b c
arr (a -> b -> a
forall a b. a -> b -> a
const a
x ))liftA2 :: (a -> b -> c)
-> WrappedArrow a b a -> WrappedArrow a b b -> WrappedArrow a b c
liftA2 a -> b -> c
f (WrapArrow a b a
u )(WrapArrow a b b
v )=a b c -> WrappedArrow a b c
forall (a :: * -> * -> *) b c. a b c -> WrappedArrow a b c
WrapArrow (a b a
u a b a -> a b b -> a b (a, b)
forall (a :: * -> * -> *) b c c'.
Arrow a =>
a b c -> a b c' -> a b (c, c')
&&& a b b
v a b (a, b) -> a (a, b) c -> a b c
forall k (cat :: k -> k -> *) (a :: k) (b :: k) (c :: k).
Category cat =>
cat a b -> cat b c -> cat a c
>>> ((a, b) -> c) -> a (a, b) c
forall (a :: * -> * -> *) b c. Arrow a => (b -> c) -> a b c
arr ((a -> b -> c) -> (a, b) -> c
forall a b c. (a -> b -> c) -> (a, b) -> c
uncurry a -> b -> c
f ))-- | @since 2.01instance(ArrowZero a ,ArrowPlus a )=>Alternative (WrappedArrow a b )whereempty :: WrappedArrow a b a
empty =a b a -> WrappedArrow a b a
forall (a :: * -> * -> *) b c. a b c -> WrappedArrow a b c
WrapArrow a b a
forall (a :: * -> * -> *) b c. ArrowZero a => a b c
zeroArrow WrapArrow a b a
u <|> :: WrappedArrow a b a -> WrappedArrow a b a -> WrappedArrow a b a
<|> WrapArrow a b a
v =a b a -> WrappedArrow a b a
forall (a :: * -> * -> *) b c. a b c -> WrappedArrow a b c
WrapArrow (a b a
u a b a -> a b a -> a b a
forall (a :: * -> * -> *) b c.
ArrowPlus a =>
a b c -> a b c -> a b c
<+> a b a
v )-- | Lists, but with an 'Applicative' functor based on zipping.newtypeZipList a =ZipList {ZipList a -> [a]
getZipList ::[a ]}deriving(Show -- ^ @since 4.7.0.0,Eq-- ^ @since 4.7.0.0,Ord-- ^ @since 4.7.0.0,Read -- ^ @since 4.7.0.0,Functor -- ^ @since 2.01,Foldable -- ^ @since 4.9.0.0,Generic -- ^ @since 4.7.0.0,Generic1 -- ^ @since 4.7.0.0)-- See Data.Traversable for Traversable instance due to import loops-- |-- > f <$> ZipList xs1 <*> ... <*> ZipList xsN-- > = ZipList (zipWithN f xs1 ... xsN)---- where @zipWithN@ refers to the @zipWith@ function of the appropriate arity-- (@zipWith@, @zipWith3@, @zipWith4@, ...). For example:---- > (\a b c -> stimes c [a, b]) <$> ZipList "abcd" <*> ZipList "567" <*> ZipList [1..]-- > = ZipList (zipWith3 (\a b c -> stimes c [a, b]) "abcd" "567" [1..])-- > = ZipList {getZipList = ["a5","b6b6","c7c7c7"]}---- @since 2.01instanceApplicative ZipList wherepure :: a -> ZipList a
pure a
x =[a] -> ZipList a
forall a. [a] -> ZipList a
ZipList (a -> [a]
forall a. a -> [a]
repeat a
x )liftA2 :: (a -> b -> c) -> ZipList a -> ZipList b -> ZipList c
liftA2 a -> b -> c
f (ZipList [a]
xs )(ZipList [b]
ys )=[c] -> ZipList c
forall a. [a] -> ZipList a
ZipList ((a -> b -> c) -> [a] -> [b] -> [c]
forall a b c. (a -> b -> c) -> [a] -> [b] -> [c]
zipWith a -> b -> c
f [a]
xs [b]
ys )-- | @since 4.11.0.0instanceAlternative ZipList whereempty :: ZipList a
empty =[a] -> ZipList a
forall a. [a] -> ZipList a
ZipList []ZipList [a]
xs <|> :: ZipList a -> ZipList a -> ZipList a
<|> ZipList [a]
ys =[a] -> ZipList a
forall a. [a] -> ZipList a
ZipList ([a]
xs [a] -> [a] -> [a]
forall a. [a] -> [a] -> [a]
++ Int -> [a] -> [a]
forall a. Int -> [a] -> [a]
drop ([a] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [a]
xs )[a]
ys )-- extra functions-- | One or none.optional ::Alternative f =>f a ->f (Maybe a )optional :: f a -> f (Maybe a)
optional f a
v =a -> Maybe a
forall a. a -> Maybe a
Just (a -> Maybe a) -> f a -> f (Maybe a)
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> f a
v f (Maybe a) -> f (Maybe a) -> f (Maybe a)
forall (f :: * -> *) a. Alternative f => f a -> f a -> f a
<|> Maybe a -> f (Maybe a)
forall (f :: * -> *) a. Applicative f => a -> f a
pure Maybe a
forall a. Maybe a
Nothing