incipit-base-0.5.1.0: A Prelude for Polysemy – Base Reexports
Safe HaskellSafe-Inferred
LanguageHaskell2010

Incipit.Base

Description

Reexports from base.

Synopsis

Documentation

class Functor f => Applicative (f :: Type -> Type) where Source #

A functor with application, providing operations to

  • embed pure expressions (pure), and
  • sequence computations and combine their results (<*> and liftA2).

A minimal complete definition must include implementations of pure and of either <*> or liftA2. If it defines both, then they must behave the same as their default definitions:

(<*>) = liftA2 id
liftA2 f x y = f <$> x <*> y

Further, any definition must satisfy the following:

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

The other methods have the following default definitions, which may be overridden with equivalent specialized implementations:

As a consequence of these laws, the Functor instance for f will satisfy

It may be useful to note that supposing

forall x y. p (q x y) = f x . g y

it follows from the above that

liftA2 p (liftA2 q u v) = liftA2 f u . liftA2 g v

If f is also a Monad, it should satisfy

(which implies that pure and <*> satisfy the applicative functor laws).

Minimal complete definition

pure, ((<*>) | liftA2)

Methods

pure :: a -> f a Source #

Lift a value.

(<*>) :: f (a -> b) -> f a -> f b infixl 4 Source #

Sequential application.

A few functors support an implementation of <*> that is more efficient than the default one.

Example

Expand

Used in combination with (<$>), (<*>) can be used to build a record.

>>> data MyState = MyState {arg1 :: Foo, arg2 :: Bar, arg3 :: Baz}
>>> produceFoo :: Applicative f => f Foo
>>> produceBar :: Applicative f => f Bar
>>> produceBaz :: Applicative f => f Baz
>>> mkState :: Applicative f => f MyState
>>> mkState = MyState <$> produceFoo <*> produceBar <*> produceBaz

liftA2 :: (a -> b -> c) -> f a -> f b -> f c Source #

Lift a binary function to actions.

Some functors support an implementation of liftA2 that is more efficient than the default one. In particular, if fmap is an expensive operation, it is likely better to use liftA2 than to fmap over the structure and then use <*>.

This became a typeclass method in 4.10.0.0. Prior to that, it was a function defined in terms of <*> and fmap.

Example

Expand
>>> liftA2 (,) (Just 3) (Just 5)
Just (3,5)

(*>) :: f a -> f b -> f b infixl 4 Source #

Sequence actions, discarding the value of the first argument.

Examples

Expand

If used in conjunction with the Applicative instance for Maybe, you can chain Maybe computations, with a possible "early return" in case of Nothing.

>>> Just 2 *> Just 3
Just 3
>>> Nothing *> Just 3
Nothing

Of course a more interesting use case would be to have effectful computations instead of just returning pure values.

>>> import Data.Char
>>> import Text.ParserCombinators.ReadP
>>> let p = string "my name is " *> munch1 isAlpha <* eof
>>> readP_to_S p "my name is Simon"
[("Simon","")]

(<*) :: f a -> f b -> f a infixl 4 Source #

Sequence actions, discarding the value of the second argument.

Instances

Instances details
Applicative ZipList
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: base-2.1

Instance details

Defined in Control.Applicative

Methods

pure :: a -> ZipList a Source #

(<*>) :: ZipList (a -> b) -> ZipList a -> ZipList b Source #

liftA2 :: (a -> b -> c) -> ZipList a -> ZipList b -> ZipList c Source #

(*>) :: ZipList a -> ZipList b -> ZipList b Source #

(<*) :: ZipList a -> ZipList b -> ZipList a Source #

Applicative Complex

Since: base-4.9.0.0

Instance details

Defined in Data.Complex

Methods

pure :: a -> Complex a Source #

(<*>) :: Complex (a -> b) -> Complex a -> Complex b Source #

liftA2 :: (a -> b -> c) -> Complex a -> Complex b -> Complex c Source #

(*>) :: Complex a -> Complex b -> Complex b Source #

(<*) :: Complex a -> Complex b -> Complex a Source #

Applicative Identity

Since: base-4.8.0.0

Instance details

Defined in Data.Functor.Identity

Methods

pure :: a -> Identity a Source #

(<*>) :: Identity (a -> b) -> Identity a -> Identity b Source #

liftA2 :: (a -> b -> c) -> Identity a -> Identity b -> Identity c Source #

(*>) :: Identity a -> Identity b -> Identity b Source #

(<*) :: Identity a -> Identity b -> Identity a Source #

Applicative First

Since: base-4.8.0.0

Instance details

Defined in Data.Monoid

Methods

pure :: a -> First a Source #

(<*>) :: First (a -> b) -> First a -> First b Source #

liftA2 :: (a -> b -> c) -> First a -> First b -> First c Source #

(*>) :: First a -> First b -> First b Source #

(<*) :: First a -> First b -> First a Source #

Applicative Last

Since: base-4.8.0.0

Instance details

Defined in Data.Monoid

Methods

pure :: a -> Last a Source #

(<*>) :: Last (a -> b) -> Last a -> Last b Source #

liftA2 :: (a -> b -> c) -> Last a -> Last b -> Last c Source #

(*>) :: Last a -> Last b -> Last b Source #

(<*) :: Last a -> Last b -> Last a Source #

Applicative Down

Since: base-4.11.0.0

Instance details

Defined in Data.Ord

Methods

pure :: a -> Down a Source #

(<*>) :: Down (a -> b) -> Down a -> Down b Source #

liftA2 :: (a -> b -> c) -> Down a -> Down b -> Down c Source #

(*>) :: Down a -> Down b -> Down b Source #

(<*) :: Down a -> Down b -> Down a Source #

Applicative First

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Methods

pure :: a -> First a Source #

(<*>) :: First (a -> b) -> First a -> First b Source #

liftA2 :: (a -> b -> c) -> First a -> First b -> First c Source #

(*>) :: First a -> First b -> First b Source #

(<*) :: First a -> First b -> First a Source #

Applicative Last

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Methods

pure :: a -> Last a Source #

(<*>) :: Last (a -> b) -> Last a -> Last b Source #

liftA2 :: (a -> b -> c) -> Last a -> Last b -> Last c Source #

(*>) :: Last a -> Last b -> Last b Source #

(<*) :: Last a -> Last b -> Last a Source #

Applicative Max

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Methods

pure :: a -> Max a Source #

(<*>) :: Max (a -> b) -> Max a -> Max b Source #

liftA2 :: (a -> b -> c) -> Max a -> Max b -> Max c Source #

(*>) :: Max a -> Max b -> Max b Source #

(<*) :: Max a -> Max b -> Max a Source #

Applicative Min

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Methods

pure :: a -> Min a Source #

(<*>) :: Min (a -> b) -> Min a -> Min b Source #

liftA2 :: (a -> b -> c) -> Min a -> Min b -> Min c Source #

(*>) :: Min a -> Min b -> Min b Source #

(<*) :: Min a -> Min b -> Min a Source #

Applicative Par1

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

pure :: a -> Par1 a Source #

(<*>) :: Par1 (a -> b) -> Par1 a -> Par1 b Source #

liftA2 :: (a -> b -> c) -> Par1 a -> Par1 b -> Par1 c Source #

(*>) :: Par1 a -> Par1 b -> Par1 b Source #

(<*) :: Par1 a -> Par1 b -> Par1 a Source #

Applicative P

Since: base-4.5.0.0

Instance details

Defined in Text.ParserCombinators.ReadP

Methods

pure :: a -> P a Source #

(<*>) :: P (a -> b) -> P a -> P b Source #

liftA2 :: (a -> b -> c) -> P a -> P b -> P c Source #

(*>) :: P a -> P b -> P b Source #

(<*) :: P a -> P b -> P a Source #

Applicative ReadP

Since: base-4.6.0.0

Instance details

Defined in Text.ParserCombinators.ReadP

Methods

pure :: a -> ReadP a Source #

(<*>) :: ReadP (a -> b) -> ReadP a -> ReadP b Source #

liftA2 :: (a -> b -> c) -> ReadP a -> ReadP b -> ReadP c Source #

(*>) :: ReadP a -> ReadP b -> ReadP b Source #

(<*) :: ReadP a -> ReadP b -> ReadP a Source #

Applicative Seq

Since: containers-0.5.4

Instance details

Defined in Data.Sequence.Internal

Methods

pure :: a -> Seq a Source #

(<*>) :: Seq (a -> b) -> Seq a -> Seq b Source #

liftA2 :: (a -> b -> c) -> Seq a -> Seq b -> Seq c Source #

(*>) :: Seq a -> Seq b -> Seq b Source #

(<*) :: Seq a -> Seq b -> Seq a Source #

Applicative DList 
Instance details

Defined in Data.DList.Internal

Methods

pure :: a -> DList a Source #

(<*>) :: DList (a -> b) -> DList a -> DList b Source #

liftA2 :: (a -> b -> c) -> DList a -> DList b -> DList c Source #

(*>) :: DList a -> DList b -> DList b Source #

(<*) :: DList a -> DList b -> DList a Source #

Applicative IO

Since: base-2.1

Instance details

Defined in GHC.Base

Methods

pure :: a -> IO a Source #

(<*>) :: IO (a -> b) -> IO a -> IO b Source #

liftA2 :: (a -> b -> c) -> IO a -> IO b -> IO c Source #

(*>) :: IO a -> IO b -> IO b Source #

(<*) :: IO a -> IO b -> IO a Source #

Applicative NonEmpty

Since: base-4.9.0.0

Instance details

Defined in GHC.Base

Methods

pure :: a -> NonEmpty a Source #

(<*>) :: NonEmpty (a -> b) -> NonEmpty a -> NonEmpty b Source #

liftA2 :: (a -> b -> c) -> NonEmpty a -> NonEmpty b -> NonEmpty c Source #

(*>) :: NonEmpty a -> NonEmpty b -> NonEmpty b Source #

(<*) :: NonEmpty a -> NonEmpty b -> NonEmpty a Source #

Applicative Maybe

Since: base-2.1

Instance details

Defined in GHC.Base

Methods

pure :: a -> Maybe a Source #

(<*>) :: Maybe (a -> b) -> Maybe a -> Maybe b Source #

liftA2 :: (a -> b -> c) -> Maybe a -> Maybe b -> Maybe c Source #

(*>) :: Maybe a -> Maybe b -> Maybe b Source #

(<*) :: Maybe a -> Maybe b -> Maybe a Source #

Applicative Solo

Since: base-4.15

Instance details

Defined in GHC.Base

Methods

pure :: a -> Solo a Source #

(<*>) :: Solo (a -> b) -> Solo a -> Solo b Source #

liftA2 :: (a -> b -> c) -> Solo a -> Solo b -> Solo c Source #

(*>) :: Solo a -> Solo b -> Solo b Source #

(<*) :: Solo a -> Solo b -> Solo a Source #

Applicative []

Since: base-2.1

Instance details

Defined in GHC.Base

Methods

pure :: a -> [a] Source #

(<*>) :: [a -> b] -> [a] -> [b] Source #

liftA2 :: (a -> b -> c) -> [a] -> [b] -> [c] Source #

(*>) :: [a] -> [b] -> [b] Source #

(<*) :: [a] -> [b] -> [a] Source #

Monad m => Applicative (WrappedMonad m)

Since: base-2.1

Instance details

Defined in Control.Applicative

Methods

pure :: a -> WrappedMonad m a Source #

(<*>) :: WrappedMonad m (a -> b) -> WrappedMonad m a -> WrappedMonad m b Source #

liftA2 :: (a -> b -> c) -> WrappedMonad m a -> WrappedMonad m b -> WrappedMonad m c Source #

(*>) :: WrappedMonad m a -> WrappedMonad m b -> WrappedMonad m b Source #

(<*) :: WrappedMonad m a -> WrappedMonad m b -> WrappedMonad m a Source #

Arrow a => Applicative (ArrowMonad a)

Since: base-4.6.0.0

Instance details

Defined in Control.Arrow

Methods

pure :: a0 -> ArrowMonad a a0 Source #

(<*>) :: ArrowMonad a (a0 -> b) -> ArrowMonad a a0 -> ArrowMonad a b Source #

liftA2 :: (a0 -> b -> c) -> ArrowMonad a a0 -> ArrowMonad a b -> ArrowMonad a c Source #

(*>) :: ArrowMonad a a0 -> ArrowMonad a b -> ArrowMonad a b Source #

(<*) :: ArrowMonad a a0 -> ArrowMonad a b -> ArrowMonad a a0 Source #

Applicative (Either e)

Since: base-3.0

Instance details

Defined in Data.Either

Methods

pure :: a -> Either e a Source #

(<*>) :: Either e (a -> b) -> Either e a -> Either e b Source #

liftA2 :: (a -> b -> c) -> Either e a -> Either e b -> Either e c Source #

(*>) :: Either e a -> Either e b -> Either e b Source #

(<*) :: Either e a -> Either e b -> Either e a Source #

Applicative (Proxy :: Type -> Type)

Since: base-4.7.0.0

Instance details

Defined in Data.Proxy

Methods

pure :: a -> Proxy a Source #

(<*>) :: Proxy (a -> b) -> Proxy a -> Proxy b Source #

liftA2 :: (a -> b -> c) -> Proxy a -> Proxy b -> Proxy c Source #

(*>) :: Proxy a -> Proxy b -> Proxy b Source #

(<*) :: Proxy a -> Proxy b -> Proxy a Source #

Applicative (U1 :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

pure :: a -> U1 a Source #

(<*>) :: U1 (a -> b) -> U1 a -> U1 b Source #

liftA2 :: (a -> b -> c) -> U1 a -> U1 b -> U1 c Source #

(*>) :: U1 a -> U1 b -> U1 b Source #

(<*) :: U1 a -> U1 b -> U1 a Source #

Monoid a => Applicative ((,) a)

For tuples, the Monoid constraint on a determines how the first values merge. For example, Strings concatenate:

("hello ", (+15)) <*> ("world!", 2002)
("hello world!",2017)

Since: base-2.1

Instance details

Defined in GHC.Base

Methods

pure :: a0 -> (a, a0) Source #

(<*>) :: (a, a0 -> b) -> (a, a0) -> (a, b) Source #

liftA2 :: (a0 -> b -> c) -> (a, a0) -> (a, b) -> (a, c) Source #

(*>) :: (a, a0) -> (a, b) -> (a, b) Source #

(<*) :: (a, a0) -> (a, b) -> (a, a0) Source #

Arrow a => Applicative (WrappedArrow a b)

Since: base-2.1

Instance details

Defined in Control.Applicative

Methods

pure :: a0 -> WrappedArrow a b a0 Source #

(<*>) :: WrappedArrow a b (a0 -> b0) -> WrappedArrow a b a0 -> WrappedArrow a b b0 Source #

liftA2 :: (a0 -> b0 -> c) -> WrappedArrow a b a0 -> WrappedArrow a b b0 -> WrappedArrow a b c Source #

(*>) :: WrappedArrow a b a0 -> WrappedArrow a b b0 -> WrappedArrow a b b0 Source #

(<*) :: WrappedArrow a b a0 -> WrappedArrow a b b0 -> WrappedArrow a b a0 Source #

Applicative m => Applicative (Kleisli m a)

Since: base-4.14.0.0

Instance details

Defined in Control.Arrow

Methods

pure :: a0 -> Kleisli m a a0 Source #

(<*>) :: Kleisli m a (a0 -> b) -> Kleisli m a a0 -> Kleisli m a b Source #

liftA2 :: (a0 -> b -> c) -> Kleisli m a a0 -> Kleisli m a b -> Kleisli m a c Source #

(*>) :: Kleisli m a a0 -> Kleisli m a b -> Kleisli m a b Source #

(<*) :: Kleisli m a a0 -> Kleisli m a b -> Kleisli m a a0 Source #

Monoid m => Applicative (Const m :: Type -> Type)

Since: base-2.0.1

Instance details

Defined in Data.Functor.Const

Methods

pure :: a -> Const m a Source #

(<*>) :: Const m (a -> b) -> Const m a -> Const m b Source #

liftA2 :: (a -> b -> c) -> Const m a -> Const m b -> Const m c Source #

(*>) :: Const m a -> Const m b -> Const m b Source #

(<*) :: Const m a -> Const m b -> Const m a Source #

Applicative f => Applicative (Ap f)

Since: base-4.12.0.0

Instance details

Defined in Data.Monoid

Methods

pure :: a -> Ap f a Source #

(<*>) :: Ap f (a -> b) -> Ap f a -> Ap f b Source #

liftA2 :: (a -> b -> c) -> Ap f a -> Ap f b -> Ap f c Source #

(*>) :: Ap f a -> Ap f b -> Ap f b Source #

(<*) :: Ap f a -> Ap f b -> Ap f a Source #

(Generic1 f, Applicative (Rep1 f)) => Applicative (Generically1 f)

Since: base-4.17.0.0

Instance details

Defined in GHC.Generics

Methods

pure :: a -> Generically1 f a Source #

(<*>) :: Generically1 f (a -> b) -> Generically1 f a -> Generically1 f b Source #

liftA2 :: (a -> b -> c) -> Generically1 f a -> Generically1 f b -> Generically1 f c Source #

(*>) :: Generically1 f a -> Generically1 f b -> Generically1 f b Source #

(<*) :: Generically1 f a -> Generically1 f b -> Generically1 f a Source #

Applicative f => Applicative (Rec1 f)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

pure :: a -> Rec1 f a Source #

(<*>) :: Rec1 f (a -> b) -> Rec1 f a -> Rec1 f b Source #

liftA2 :: (a -> b -> c) -> Rec1 f a -> Rec1 f b -> Rec1 f c Source #

(*>) :: Rec1 f a -> Rec1 f b -> Rec1 f b Source #

(<*) :: Rec1 f a -> Rec1 f b -> Rec1 f a Source #

(Applicative f, Monad f) => Applicative (WhenMissing f x)

Equivalent to ReaderT k (ReaderT x (MaybeT f)).

Since: containers-0.5.9

Instance details

Defined in Data.IntMap.Internal

Methods

pure :: a -> WhenMissing f x a Source #

(<*>) :: WhenMissing f x (a -> b) -> WhenMissing f x a -> WhenMissing f x b Source #

liftA2 :: (a -> b -> c) -> WhenMissing f x a -> WhenMissing f x b -> WhenMissing f x c Source #

(*>) :: WhenMissing f x a -> WhenMissing f x b -> WhenMissing f x b Source #

(<*) :: WhenMissing f x a -> WhenMissing f x b -> WhenMissing f x a Source #

(Monoid a, Monoid b) => Applicative ((,,) a b)

Since: base-4.14.0.0

Instance details

Defined in GHC.Base

Methods

pure :: a0 -> (a, b, a0) Source #

(<*>) :: (a, b, a0 -> b0) -> (a, b, a0) -> (a, b, b0) Source #

liftA2 :: (a0 -> b0 -> c) -> (a, b, a0) -> (a, b, b0) -> (a, b, c) Source #

(*>) :: (a, b, a0) -> (a, b, b0) -> (a, b, b0) Source #

(<*) :: (a, b, a0) -> (a, b, b0) -> (a, b, a0) Source #

(Applicative f, Applicative g) => Applicative (Product f g)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Product

Methods

pure :: a -> Product f g a Source #

(<*>) :: Product f g (a -> b) -> Product f g a -> Product f g b Source #

liftA2 :: (a -> b -> c) -> Product f g a -> Product f g b -> Product f g c Source #

(*>) :: Product f g a -> Product f g b -> Product f g b Source #

(<*) :: Product f g a -> Product f g b -> Product f g a Source #

(Applicative f, Applicative g) => Applicative (f :*: g)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

pure :: a -> (f :*: g) a Source #

(<*>) :: (f :*: g) (a -> b) -> (f :*: g) a -> (f :*: g) b Source #

liftA2 :: (a -> b -> c) -> (f :*: g) a -> (f :*: g) b -> (f :*: g) c Source #

(*>) :: (f :*: g) a -> (f :*: g) b -> (f :*: g) b Source #

(<*) :: (f :*: g) a -> (f :*: g) b -> (f :*: g) a Source #

Monoid c => Applicative (K1 i c :: Type -> Type)

Since: base-4.12.0.0

Instance details

Defined in GHC.Generics

Methods

pure :: a -> K1 i c a Source #

(<*>) :: K1 i c (a -> b) -> K1 i c a -> K1 i c b Source #

liftA2 :: (a -> b -> c0) -> K1 i c a -> K1 i c b -> K1 i c c0 Source #

(*>) :: K1 i c a -> K1 i c b -> K1 i c b Source #

(<*) :: K1 i c a -> K1 i c b -> K1 i c a Source #

(Monad f, Applicative f) => Applicative (WhenMatched f x y)

Equivalent to ReaderT Key (ReaderT x (ReaderT y (MaybeT f)))

Since: containers-0.5.9

Instance details

Defined in Data.IntMap.Internal

Methods

pure :: a -> WhenMatched f x y a Source #

(<*>) :: WhenMatched f x y (a -> b) -> WhenMatched f x y a -> WhenMatched f x y b Source #

liftA2 :: (a -> b -> c) -> WhenMatched f x y a -> WhenMatched f x y b -> WhenMatched f x y c Source #

(*>) :: WhenMatched f x y a -> WhenMatched f x y b -> WhenMatched f x y b Source #

(<*) :: WhenMatched f x y a -> WhenMatched f x y b -> WhenMatched f x y a Source #

(Applicative f, Monad f) => Applicative (WhenMissing f k x)

Equivalent to ReaderT k (ReaderT x (MaybeT f)) .

Since: containers-0.5.9

Instance details

Defined in Data.Map.Internal

Methods

pure :: a -> WhenMissing f k x a Source #

(<*>) :: WhenMissing f k x (a -> b) -> WhenMissing f k x a -> WhenMissing f k x b Source #

liftA2 :: (a -> b -> c) -> WhenMissing f k x a -> WhenMissing f k x b -> WhenMissing f k x c Source #

(*>) :: WhenMissing f k x a -> WhenMissing f k x b -> WhenMissing f k x b Source #

(<*) :: WhenMissing f k x a -> WhenMissing f k x b -> WhenMissing f k x a Source #

(Monoid a, Monoid b, Monoid c) => Applicative ((,,,) a b c)

Since: base-4.14.0.0

Instance details

Defined in GHC.Base

Methods

pure :: a0 -> (a, b, c, a0) Source #

(<*>) :: (a, b, c, a0 -> b0) -> (a, b, c, a0) -> (a, b, c, b0) Source #

liftA2 :: (a0 -> b0 -> c0) -> (a, b, c, a0) -> (a, b, c, b0) -> (a, b, c, c0) Source #

(*>) :: (a, b, c, a0) -> (a, b, c, b0) -> (a, b, c, b0) Source #

(<*) :: (a, b, c, a0) -> (a, b, c, b0) -> (a, b, c, a0) Source #

Applicative ((->) r)

Since: base-2.1

Instance details

Defined in GHC.Base

Methods

pure :: a -> r -> a Source #

(<*>) :: (r -> (a -> b)) -> (r -> a) -> r -> b Source #

liftA2 :: (a -> b -> c) -> (r -> a) -> (r -> b) -> r -> c Source #

(*>) :: (r -> a) -> (r -> b) -> r -> b Source #

(<*) :: (r -> a) -> (r -> b) -> r -> a Source #

(Applicative f, Applicative g) => Applicative (Compose f g)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Compose

Methods

pure :: a -> Compose f g a Source #

(<*>) :: Compose f g (a -> b) -> Compose f g a -> Compose f g b Source #

liftA2 :: (a -> b -> c) -> Compose f g a -> Compose f g b -> Compose f g c Source #

(*>) :: Compose f g a -> Compose f g b -> Compose f g b Source #

(<*) :: Compose f g a -> Compose f g b -> Compose f g a Source #

(Applicative f, Applicative g) => Applicative (f :.: g)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

pure :: a -> (f :.: g) a Source #

(<*>) :: (f :.: g) (a -> b) -> (f :.: g) a -> (f :.: g) b Source #

liftA2 :: (a -> b -> c) -> (f :.: g) a -> (f :.: g) b -> (f :.: g) c Source #

(*>) :: (f :.: g) a -> (f :.: g) b -> (f :.: g) b Source #

(<*) :: (f :.: g) a -> (f :.: g) b -> (f :.: g) a Source #

Applicative f => Applicative (M1 i c f)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

pure :: a -> M1 i c f a Source #

(<*>) :: M1 i c f (a -> b) -> M1 i c f a -> M1 i c f b Source #

liftA2 :: (a -> b -> c0) -> M1 i c f a -> M1 i c f b -> M1 i c f c0 Source #

(*>) :: M1 i c f a -> M1 i c f b -> M1 i c f b Source #

(<*) :: M1 i c f a -> M1 i c f b -> M1 i c f a Source #

(Monad f, Applicative f) => Applicative (WhenMatched f k x y)

Equivalent to ReaderT k (ReaderT x (ReaderT y (MaybeT f)))

Since: containers-0.5.9

Instance details

Defined in Data.Map.Internal

Methods

pure :: a -> WhenMatched f k x y a Source #

(<*>) :: WhenMatched f k x y (a -> b) -> WhenMatched f k x y a -> WhenMatched f k x y b Source #

liftA2 :: (a -> b -> c) -> WhenMatched f k x y a -> WhenMatched f k x y b -> WhenMatched f k x y c Source #

(*>) :: WhenMatched f k x y a -> WhenMatched f k x y b -> WhenMatched f k x y b Source #

(<*) :: WhenMatched f k x y a -> WhenMatched f k x y b -> WhenMatched f k x y a Source #

class Applicative f => Alternative (f :: Type -> Type) where Source #

A monoid on applicative functors.

If defined, some and many should be the least solutions of the equations:

Minimal complete definition

empty, (<|>)

Methods

empty :: f a Source #

The identity of <|>

(<|>) :: f a -> f a -> f a infixl 3 Source #

An associative binary operation

some :: f a -> f [a] Source #

One or more.

many :: f a -> f [a] Source #

Zero or more.

Instances

Instances details
Alternative ZipList

Since: base-4.11.0.0

Instance details

Defined in Control.Applicative

Alternative P

Since: base-4.5.0.0

Instance details

Defined in Text.ParserCombinators.ReadP

Methods

empty :: P a Source #

(<|>) :: P a -> P a -> P a Source #

some :: P a -> P [a] Source #

many :: P a -> P [a] Source #

Alternative ReadP

Since: base-4.6.0.0

Instance details

Defined in Text.ParserCombinators.ReadP

Methods

empty :: ReadP a Source #

(<|>) :: ReadP a -> ReadP a -> ReadP a Source #

some :: ReadP a -> ReadP [a] Source #

many :: ReadP a -> ReadP [a] Source #

Alternative Seq

Since: containers-0.5.4

Instance details

Defined in Data.Sequence.Internal

Methods

empty :: Seq a Source #

(<|>) :: Seq a -> Seq a -> Seq a Source #

some :: Seq a -> Seq [a] Source #

many :: Seq a -> Seq [a] Source #

Alternative DList 
Instance details

Defined in Data.DList.Internal

Methods

empty :: DList a Source #

(<|>) :: DList a -> DList a -> DList a Source #

some :: DList a -> DList [a] Source #

many :: DList a -> DList [a] Source #

Alternative IO

Since: base-4.9.0.0

Instance details

Defined in GHC.Base

Methods

empty :: IO a Source #

(<|>) :: IO a -> IO a -> IO a Source #

some :: IO a -> IO [a] Source #

many :: IO a -> IO [a] Source #

Alternative Maybe

Since: base-2.1

Instance details

Defined in GHC.Base

Methods

empty :: Maybe a Source #

(<|>) :: Maybe a -> Maybe a -> Maybe a Source #

some :: Maybe a -> Maybe [a] Source #

many :: Maybe a -> Maybe [a] Source #

Alternative []

Since: base-2.1

Instance details

Defined in GHC.Base

Methods

empty :: [a] Source #

(<|>) :: [a] -> [a] -> [a] Source #

some :: [a] -> [[a]] Source #

many :: [a] -> [[a]] Source #

MonadPlus m => Alternative (WrappedMonad m)

Since: base-2.1

Instance details

Defined in Control.Applicative

ArrowPlus a => Alternative (ArrowMonad a)

Since: base-4.6.0.0

Instance details

Defined in Control.Arrow

Methods

empty :: ArrowMonad a a0 Source #

(<|>) :: ArrowMonad a a0 -> ArrowMonad a a0 -> ArrowMonad a a0 Source #

some :: ArrowMonad a a0 -> ArrowMonad a [a0] Source #

many :: ArrowMonad a a0 -> ArrowMonad a [a0] Source #

Alternative (Proxy :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in Data.Proxy

Methods

empty :: Proxy a Source #

(<|>) :: Proxy a -> Proxy a -> Proxy a Source #

some :: Proxy a -> Proxy [a] Source #

many :: Proxy a -> Proxy [a] Source #

Alternative (U1 :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

empty :: U1 a Source #

(<|>) :: U1 a -> U1 a -> U1 a Source #

some :: U1 a -> U1 [a] Source #

many :: U1 a -> U1 [a] Source #

(ArrowZero a, ArrowPlus a) => Alternative (WrappedArrow a b)

Since: base-2.1

Instance details

Defined in Control.Applicative

Methods

empty :: WrappedArrow a b a0 Source #

(<|>) :: WrappedArrow a b a0 -> WrappedArrow a b a0 -> WrappedArrow a b a0 Source #

some :: WrappedArrow a b a0 -> WrappedArrow a b [a0] Source #

many :: WrappedArrow a b a0 -> WrappedArrow a b [a0] Source #

Alternative m => Alternative (Kleisli m a)

Since: base-4.14.0.0

Instance details

Defined in Control.Arrow

Methods

empty :: Kleisli m a a0 Source #

(<|>) :: Kleisli m a a0 -> Kleisli m a a0 -> Kleisli m a a0 Source #

some :: Kleisli m a a0 -> Kleisli m a [a0] Source #

many :: Kleisli m a a0 -> Kleisli m a [a0] Source #

Alternative f => Alternative (Ap f)

Since: base-4.12.0.0

Instance details

Defined in Data.Monoid

Methods

empty :: Ap f a Source #

(<|>) :: Ap f a -> Ap f a -> Ap f a Source #

some :: Ap f a -> Ap f [a] Source #

many :: Ap f a -> Ap f [a] Source #

(Generic1 f, Alternative (Rep1 f)) => Alternative (Generically1 f)

Since: base-4.17.0.0

Instance details

Defined in GHC.Generics

Alternative f => Alternative (Rec1 f)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

empty :: Rec1 f a Source #

(<|>) :: Rec1 f a -> Rec1 f a -> Rec1 f a Source #

some :: Rec1 f a -> Rec1 f [a] Source #

many :: Rec1 f a -> Rec1 f [a] Source #

(Alternative f, Alternative g) => Alternative (Product f g)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Product

Methods

empty :: Product f g a Source #

(<|>) :: Product f g a -> Product f g a -> Product f g a Source #

some :: Product f g a -> Product f g [a] Source #

many :: Product f g a -> Product f g [a] Source #

(Alternative f, Alternative g) => Alternative (f :*: g)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

empty :: (f :*: g) a Source #

(<|>) :: (f :*: g) a -> (f :*: g) a -> (f :*: g) a Source #

some :: (f :*: g) a -> (f :*: g) [a] Source #

many :: (f :*: g) a -> (f :*: g) [a] Source #

(Alternative f, Applicative g) => Alternative (Compose f g)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Compose

Methods

empty :: Compose f g a Source #

(<|>) :: Compose f g a -> Compose f g a -> Compose f g a Source #

some :: Compose f g a -> Compose f g [a] Source #

many :: Compose f g a -> Compose f g [a] Source #

(Alternative f, Applicative g) => Alternative (f :.: g)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

empty :: (f :.: g) a Source #

(<|>) :: (f :.: g) a -> (f :.: g) a -> (f :.: g) a Source #

some :: (f :.: g) a -> (f :.: g) [a] Source #

many :: (f :.: g) a -> (f :.: g) [a] Source #

Alternative f => Alternative (M1 i c f)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

empty :: M1 i c f a Source #

(<|>) :: M1 i c f a -> M1 i c f a -> M1 i c f a Source #

some :: M1 i c f a -> M1 i c f [a] Source #

many :: M1 i c f a -> M1 i c f [a] Source #

newtype Const a (b :: k) Source #

The Const functor.

Constructors

Const 

Fields

Instances

Instances details
Generic1 (Const a :: k -> Type) 
Instance details

Defined in Data.Functor.Const

Associated Types

type Rep1 (Const a) :: k -> Type Source #

Methods

from1 :: forall (a0 :: k0). Const a a0 -> Rep1 (Const a) a0 Source #

to1 :: forall (a0 :: k0). Rep1 (Const a) a0 -> Const a a0 Source #

Bifunctor (Const :: Type -> Type -> Type)

Since: base-4.8.0.0

Instance details

Defined in Data.Bifunctor

Methods

bimap :: (a -> b) -> (c -> d) -> Const a c -> Const b d Source #

first :: (a -> b) -> Const a c -> Const b c Source #

second :: (b -> c) -> Const a b -> Const a c Source #

Foldable (Const m :: Type -> Type)

Since: base-4.7.0.0

Instance details

Defined in Data.Functor.Const

Methods

fold :: Monoid m0 => Const m m0 -> m0 Source #

foldMap :: Monoid m0 => (a -> m0) -> Const m a -> m0 Source #

foldMap' :: Monoid m0 => (a -> m0) -> Const m a -> m0 Source #

foldr :: (a -> b -> b) -> b -> Const m a -> b Source #

foldr' :: (a -> b -> b) -> b -> Const m a -> b Source #

foldl :: (b -> a -> b) -> b -> Const m a -> b Source #

foldl' :: (b -> a -> b) -> b -> Const m a -> b Source #

foldr1 :: (a -> a -> a) -> Const m a -> a Source #

foldl1 :: (a -> a -> a) -> Const m a -> a Source #

toList :: Const m a -> [a] Source #

null :: Const m a -> Bool Source #

length :: Const m a -> Int Source #

elem :: Eq a => a -> Const m a -> Bool Source #

maximum :: Ord a => Const m a -> a Source #

minimum :: Ord a => Const m a -> a Source #

sum :: Num a => Const m a -> a Source #

product :: Num a => Const m a -> a Source #

Contravariant (Const a :: Type -> Type) 
Instance details

Defined in Data.Functor.Contravariant

Methods

contramap :: (a' -> a0) -> Const a a0 -> Const a a' Source #

(>$) :: b -> Const a b -> Const a a0 Source #

Traversable (Const m :: Type -> Type)

Since: base-4.7.0.0

Instance details

Defined in Data.Traversable

Methods

traverse :: Applicative f => (a -> f b) -> Const m a -> f (Const m b) Source #

sequenceA :: Applicative f => Const m (f a) -> f (Const m a) Source #

mapM :: Monad m0 => (a -> m0 b) -> Const m a -> m0 (Const m b) Source #

sequence :: Monad m0 => Const m (m0 a) -> m0 (Const m a) Source #

Monoid m => Applicative (Const m :: Type -> Type)

Since: base-2.0.1

Instance details

Defined in Data.Functor.Const

Methods

pure :: a -> Const m a Source #

(<*>) :: Const m (a -> b) -> Const m a -> Const m b Source #

liftA2 :: (a -> b -> c) -> Const m a -> Const m b -> Const m c Source #

(*>) :: Const m a -> Const m b -> Const m b Source #

(<*) :: Const m a -> Const m b -> Const m a Source #

Functor (Const m :: Type -> Type)

Since: base-2.1

Instance details

Defined in Data.Functor.Const

Methods

fmap :: (a -> b) -> Const m a -> Const m b Source #

(<$) :: a -> Const m b -> Const m a Source #

IsString a => IsString (Const a b)

Since: base-4.9.0.0

Instance details

Defined in Data.String

Methods

fromString :: String -> Const a b Source #

Storable a => Storable (Const a b)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Const

Methods

sizeOf :: Const a b -> Int Source #

alignment :: Const a b -> Int Source #

peekElemOff :: Ptr (Const a b) -> Int -> IO (Const a b) Source #

pokeElemOff :: Ptr (Const a b) -> Int -> Const a b -> IO () Source #

peekByteOff :: Ptr b0 -> Int -> IO (Const a b) Source #

pokeByteOff :: Ptr b0 -> Int -> Const a b -> IO () Source #

peek :: Ptr (Const a b) -> IO (Const a b) Source #

poke :: Ptr (Const a b) -> Const a b -> IO () Source #

Monoid a => Monoid (Const a b)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Const

Methods

mempty :: Const a b Source #

mappend :: Const a b -> Const a b -> Const a b Source #

mconcat :: [Const a b] -> Const a b Source #

Semigroup a => Semigroup (Const a b)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Const

Methods

(<>) :: Const a b -> Const a b -> Const a b Source #

sconcat :: NonEmpty (Const a b) -> Const a b Source #

stimes :: Integral b0 => b0 -> Const a b -> Const a b Source #

Bits a => Bits (Const a b)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Const

Methods

(.&.) :: Const a b -> Const a b -> Const a b Source #

(.|.) :: Const a b -> Const a b -> Const a b Source #

xor :: Const a b -> Const a b -> Const a b Source #

complement :: Const a b -> Const a b Source #

shift :: Const a b -> Int -> Const a b Source #

rotate :: Const a b -> Int -> Const a b Source #

zeroBits :: Const a b Source #

bit :: Int -> Const a b Source #

setBit :: Const a b -> Int -> Const a b Source #

clearBit :: Const a b -> Int -> Const a b Source #

complementBit :: Const a b -> Int -> Const a b Source #

testBit :: Const a b -> Int -> Bool Source #

bitSizeMaybe :: Const a b -> Maybe Int Source #

bitSize :: Const a b -> Int Source #

isSigned :: Const a b -> Bool Source #

shiftL :: Const a b -> Int -> Const a b Source #

unsafeShiftL :: Const a b -> Int -> Const a b Source #

shiftR :: Const a b -> Int -> Const a b Source #

unsafeShiftR :: Const a b -> Int -> Const a b Source #

rotateL :: Const a b -> Int -> Const a b Source #

rotateR :: Const a b -> Int -> Const a b Source #

popCount :: Const a b -> Int Source #

FiniteBits a => FiniteBits (Const a b)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Const

Bounded a => Bounded (Const a b)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Const

Methods

minBound :: Const a b Source #

maxBound :: Const a b Source #

Enum a => Enum (Const a b)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Const

Methods

succ :: Const a b -> Const a b Source #

pred :: Const a b -> Const a b Source #

toEnum :: Int -> Const a b Source #

fromEnum :: Const a b -> Int Source #

enumFrom :: Const a b -> [Const a b] Source #

enumFromThen :: Const a b -> Const a b -> [Const a b] Source #

enumFromTo :: Const a b -> Const a b -> [Const a b] Source #

enumFromThenTo :: Const a b -> Const a b -> Const a b -> [Const a b] Source #

Floating a => Floating (Const a b)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Const

Methods

pi :: Const a b Source #

exp :: Const a b -> Const a b Source #

log :: Const a b -> Const a b Source #

sqrt :: Const a b -> Const a b Source #

(**) :: Const a b -> Const a b -> Const a b Source #

logBase :: Const a b -> Const a b -> Const a b Source #

sin :: Const a b -> Const a b Source #

cos :: Const a b -> Const a b Source #

tan :: Const a b -> Const a b Source #

asin :: Const a b -> Const a b Source #

acos :: Const a b -> Const a b Source #

atan :: Const a b -> Const a b Source #

sinh :: Const a b -> Const a b Source #

cosh :: Const a b -> Const a b Source #

tanh :: Const a b -> Const a b Source #

asinh :: Const a b -> Const a b Source #

acosh :: Const a b -> Const a b Source #

atanh :: Const a b -> Const a b Source #

log1p :: Const a b -> Const a b Source #

expm1 :: Const a b -> Const a b Source #

log1pexp :: Const a b -> Const a b Source #

log1mexp :: Const a b -> Const a b Source #

RealFloat a => RealFloat (Const a b)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Const

Generic (Const a b) 
Instance details

Defined in Data.Functor.Const

Associated Types

type Rep (Const a b) :: Type -> Type Source #

Methods

from :: Const a b -> Rep (Const a b) x Source #

to :: Rep (Const a b) x -> Const a b Source #

Ix a => Ix (Const a b)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Const

Methods

range :: (Const a b, Const a b) -> [Const a b] Source #

index :: (Const a b, Const a b) -> Const a b -> Int Source #

unsafeIndex :: (Const a b, Const a b) -> Const a b -> Int Source #

inRange :: (Const a b, Const a b) -> Const a b -> Bool Source #

rangeSize :: (Const a b, Const a b) -> Int Source #

unsafeRangeSize :: (Const a b, Const a b) -> Int Source #

Num a => Num (Const a b)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Const

Methods

(+) :: Const a b -> Const a b -> Const a b Source #

(-) :: Const a b -> Const a b -> Const a b Source #

(*) :: Const a b -> Const a b -> Const a b Source #

negate :: Const a b -> Const a b Source #

abs :: Const a b -> Const a b Source #

signum :: Const a b -> Const a b Source #

fromInteger :: Integer -> Const a b Source #

Read a => Read (Const a b)

This instance would be equivalent to the derived instances of the Const newtype if the getConst field were removed

Since: base-4.8.0.0

Instance details

Defined in Data.Functor.Const

Fractional a => Fractional (Const a b)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Const

Methods

(/) :: Const a b -> Const a b -> Const a b Source #

recip :: Const a b -> Const a b Source #

fromRational :: Rational -> Const a b Source #

Integral a => Integral (Const a b)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Const

Methods

quot :: Const a b -> Const a b -> Const a b Source #

rem :: Const a b -> Const a b -> Const a b Source #

div :: Const a b -> Const a b -> Const a b Source #

mod :: Const a b -> Const a b -> Const a b Source #

quotRem :: Const a b -> Const a b -> (Const a b, Const a b) Source #

divMod :: Const a b -> Const a b -> (Const a b, Const a b) Source #

toInteger :: Const a b -> Integer Source #

Real a => Real (Const a b)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Const

Methods

toRational :: Const a b -> Rational Source #

RealFrac a => RealFrac (Const a b)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Const

Methods

properFraction :: Integral b0 => Const a b -> (b0, Const a b) Source #

truncate :: Integral b0 => Const a b -> b0 Source #

round :: Integral b0 => Const a b -> b0 Source #

ceiling :: Integral b0 => Const a b -> b0 Source #

floor :: Integral b0 => Const a b -> b0 Source #

Show a => Show (Const a b)

This instance would be equivalent to the derived instances of the Const newtype if the getConst field were removed

Since: base-4.8.0.0

Instance details

Defined in Data.Functor.Const

Methods

showsPrec :: Int -> Const a b -> ShowS Source #

show :: Const a b -> String Source #

showList :: [Const a b] -> ShowS Source #

Eq a => Eq (Const a b)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Const

Methods

(==) :: Const a b -> Const a b -> Bool Source #

(/=) :: Const a b -> Const a b -> Bool Source #

Ord a => Ord (Const a b)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Const

Methods

compare :: Const a b -> Const a b -> Ordering Source #

(<) :: Const a b -> Const a b -> Bool Source #

(<=) :: Const a b -> Const a b -> Bool Source #

(>) :: Const a b -> Const a b -> Bool Source #

(>=) :: Const a b -> Const a b -> Bool Source #

max :: Const a b -> Const a b -> Const a b Source #

min :: Const a b -> Const a b -> Const a b Source #

type Rep1 (Const a :: k -> Type)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Const

type Rep1 (Const a :: k -> Type) = D1 ('MetaData "Const" "Data.Functor.Const" "base" 'True) (C1 ('MetaCons "Const" 'PrefixI 'True) (S1 ('MetaSel ('Just "getConst") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 a)))
type Rep (Const a b)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Const

type Rep (Const a b) = D1 ('MetaData "Const" "Data.Functor.Const" "base" 'True) (C1 ('MetaCons "Const" 'PrefixI 'True) (S1 ('MetaSel ('Just "getConst") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 a)))

newtype ZipList a Source #

Lists, but with an Applicative functor based on zipping.

Constructors

ZipList 

Fields

Instances

Instances details
Foldable ZipList

Since: base-4.9.0.0

Instance details

Defined in Control.Applicative

Methods

fold :: Monoid m => ZipList m -> m Source #

foldMap :: Monoid m => (a -> m) -> ZipList a -> m Source #

foldMap' :: Monoid m => (a -> m) -> ZipList a -> m Source #

foldr :: (a -> b -> b) -> b -> ZipList a -> b Source #

foldr' :: (a -> b -> b) -> b -> ZipList a -> b Source #

foldl :: (b -> a -> b) -> b -> ZipList a -> b Source #

foldl' :: (b -> a -> b) -> b -> ZipList a -> b Source #

foldr1 :: (a -> a -> a) -> ZipList a -> a Source #

foldl1 :: (a -> a -> a) -> ZipList a -> a Source #

toList :: ZipList a -> [a] Source #

null :: ZipList a -> Bool Source #

length :: ZipList a -> Int Source #

elem :: Eq a => a -> ZipList a -> Bool Source #

maximum :: Ord a => ZipList a -> a Source #

minimum :: Ord a => ZipList a -> a Source #

sum :: Num a => ZipList a -> a Source #

product :: Num a => ZipList a -> a Source #

Traversable ZipList

Since: base-4.9.0.0

Instance details

Defined in Data.Traversable

Methods

traverse :: Applicative f => (a -> f b) -> ZipList a -> f (ZipList b) Source #

sequenceA :: Applicative f => ZipList (f a) -> f (ZipList a) Source #

mapM :: Monad m => (a -> m b) -> ZipList a -> m (ZipList b) Source #

sequence :: Monad m => ZipList (m a) -> m (ZipList a) Source #

Alternative ZipList

Since: base-4.11.0.0

Instance details

Defined in Control.Applicative

Applicative ZipList
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: base-2.1

Instance details

Defined in Control.Applicative

Methods

pure :: a -> ZipList a Source #

(<*>) :: ZipList (a -> b) -> ZipList a -> ZipList b Source #

liftA2 :: (a -> b -> c) -> ZipList a -> ZipList b -> ZipList c Source #

(*>) :: ZipList a -> ZipList b -> ZipList b Source #

(<*) :: ZipList a -> ZipList b -> ZipList a Source #

Functor ZipList

Since: base-2.1

Instance details

Defined in Control.Applicative

Methods

fmap :: (a -> b) -> ZipList a -> ZipList b Source #

(<$) :: a -> ZipList b -> ZipList a Source #

Generic1 ZipList 
Instance details

Defined in Control.Applicative

Associated Types

type Rep1 ZipList :: k -> Type Source #

Methods

from1 :: forall (a :: k). ZipList a -> Rep1 ZipList a Source #

to1 :: forall (a :: k). Rep1 ZipList a -> ZipList a Source #

Generic (ZipList a) 
Instance details

Defined in Control.Applicative

Associated Types

type Rep (ZipList a) :: Type -> Type Source #

Methods

from :: ZipList a -> Rep (ZipList a) x Source #

to :: Rep (ZipList a) x -> ZipList a Source #

IsList (ZipList a)

Since: base-4.15.0.0

Instance details

Defined in GHC.IsList

Associated Types

type Item (ZipList a) Source #

Methods

fromList :: [Item (ZipList a)] -> ZipList a Source #

fromListN :: Int -> [Item (ZipList a)] -> ZipList a Source #

toList :: ZipList a -> [Item (ZipList a)] Source #

Read a => Read (ZipList a)

Since: base-4.7.0.0

Instance details

Defined in Control.Applicative

Show a => Show (ZipList a)

Since: base-4.7.0.0

Instance details

Defined in Control.Applicative

Eq a => Eq (ZipList a)

Since: base-4.7.0.0

Instance details

Defined in Control.Applicative

Methods

(==) :: ZipList a -> ZipList a -> Bool Source #

(/=) :: ZipList a -> ZipList a -> Bool Source #

Ord a => Ord (ZipList a)

Since: base-4.7.0.0

Instance details

Defined in Control.Applicative

type Rep1 ZipList

Since: base-4.7.0.0

Instance details

Defined in Control.Applicative

type Rep1 ZipList = D1 ('MetaData "ZipList" "Control.Applicative" "base" 'True) (C1 ('MetaCons "ZipList" 'PrefixI 'True) (S1 ('MetaSel ('Just "getZipList") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec1 [])))
type Rep (ZipList a)

Since: base-4.7.0.0

Instance details

Defined in Control.Applicative

type Rep (ZipList a) = D1 ('MetaData "ZipList" "Control.Applicative" "base" 'True) (C1 ('MetaCons "ZipList" 'PrefixI 'True) (S1 ('MetaSel ('Just "getZipList") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 [a])))
type Item (ZipList a) 
Instance details

Defined in GHC.IsList

type Item (ZipList a) = a

(<**>) :: Applicative f => f a -> f (a -> b) -> f b infixl 4 Source #

A variant of <*> with the arguments reversed.

liftA3 :: Applicative f => (a -> b -> c -> d) -> f a -> f b -> f c -> f d Source #

Lift a ternary function to actions.

optional :: Alternative f => f a -> f (Maybe a) Source #

One or none.

It is useful for modelling any computation that is allowed to fail.

Examples

Expand

Using the Alternative instance of Control.Monad.Except, the following functions:

>>> import Control.Monad.Except
>>> canFail = throwError "it failed" :: Except String Int
>>> final = return 42                :: Except String Int

Can be combined by allowing the first function to fail:

>>> runExcept $ canFail *> final
Left "it failed"
>>> runExcept $ optional canFail *> final
Right 42

(&&&) :: Arrow a => a b c -> a b c' -> a b (c, c') infixr 3 Source #

Fanout: send the input to both argument arrows and combine their output.

The default definition may be overridden with a more efficient version if desired.

(>>>) :: forall {k} cat (a :: k) (b :: k) (c :: k). Category cat => cat a b -> cat b c -> cat a c infixr 1 Source #

Left-to-right composition

(<<<) :: forall {k} cat (b :: k) (c :: k) (a :: k). Category cat => cat b c -> cat a b -> cat a c infixr 1 Source #

Right-to-left composition

class (Typeable e, Show e) => Exception e Source #

Any type that you wish to throw or catch as an exception must be an instance of the Exception class. The simplest case is a new exception type directly below the root:

data MyException = ThisException | ThatException
    deriving Show

instance Exception MyException

The default method definitions in the Exception class do what we need in this case. You can now throw and catch ThisException and ThatException as exceptions:

*Main> throw ThisException `catch` \e -> putStrLn ("Caught " ++ show (e :: MyException))
Caught ThisException

In more complicated examples, you may wish to define a whole hierarchy of exceptions:

---------------------------------------------------------------------
-- Make the root exception type for all the exceptions in a compiler

data SomeCompilerException = forall e . Exception e => SomeCompilerException e

instance Show SomeCompilerException where
    show (SomeCompilerException e) = show e

instance Exception SomeCompilerException

compilerExceptionToException :: Exception e => e -> SomeException
compilerExceptionToException = toException . SomeCompilerException

compilerExceptionFromException :: Exception e => SomeException -> Maybe e
compilerExceptionFromException x = do
    SomeCompilerException a <- fromException x
    cast a

---------------------------------------------------------------------
-- Make a subhierarchy for exceptions in the frontend of the compiler

data SomeFrontendException = forall e . Exception e => SomeFrontendException e

instance Show SomeFrontendException where
    show (SomeFrontendException e) = show e

instance Exception SomeFrontendException where
    toException = compilerExceptionToException
    fromException = compilerExceptionFromException

frontendExceptionToException :: Exception e => e -> SomeException
frontendExceptionToException = toException . SomeFrontendException

frontendExceptionFromException :: Exception e => SomeException -> Maybe e
frontendExceptionFromException x = do
    SomeFrontendException a <- fromException x
    cast a

---------------------------------------------------------------------
-- Make an exception type for a particular frontend compiler exception

data MismatchedParentheses = MismatchedParentheses
    deriving Show

instance Exception MismatchedParentheses where
    toException   = frontendExceptionToException
    fromException = frontendExceptionFromException

We can now catch a MismatchedParentheses exception as MismatchedParentheses, SomeFrontendException or SomeCompilerException, but not other types, e.g. IOException:

*Main> throw MismatchedParentheses `catch` \e -> putStrLn ("Caught " ++ show (e :: MismatchedParentheses))
Caught MismatchedParentheses
*Main> throw MismatchedParentheses `catch` \e -> putStrLn ("Caught " ++ show (e :: SomeFrontendException))
Caught MismatchedParentheses
*Main> throw MismatchedParentheses `catch` \e -> putStrLn ("Caught " ++ show (e :: SomeCompilerException))
Caught MismatchedParentheses
*Main> throw MismatchedParentheses `catch` \e -> putStrLn ("Caught " ++ show (e :: IOException))
*** Exception: MismatchedParentheses

data SomeException Source #

The SomeException type is the root of the exception type hierarchy. When an exception of type e is thrown, behind the scenes it is encapsulated in a SomeException.

Constructors

Exception e => SomeException e 

class (Alternative m, Monad m) => MonadPlus (m :: Type -> Type) where Source #

Monads that also support choice and failure.

Minimal complete definition

Nothing

Methods

mzero :: m a Source #

The identity of mplus. It should also satisfy the equations

mzero >>= f  =  mzero
v >> mzero   =  mzero

The default definition is

mzero = empty

mplus :: m a -> m a -> m a Source #

An associative operation. The default definition is

mplus = (<|>)

Instances

Instances details
MonadPlus P

Since: base-2.1

Instance details

Defined in Text.ParserCombinators.ReadP

Methods

mzero :: P a Source #

mplus :: P a -> P a -> P a Source #

MonadPlus ReadP

Since: base-2.1

Instance details

Defined in Text.ParserCombinators.ReadP

Methods

mzero :: ReadP a Source #

mplus :: ReadP a -> ReadP a -> ReadP a Source #

MonadPlus Seq 
Instance details

Defined in Data.Sequence.Internal

Methods

mzero :: Seq a Source #

mplus :: Seq a -> Seq a -> Seq a Source #

MonadPlus DList 
Instance details

Defined in Data.DList.Internal

Methods

mzero :: DList a Source #

mplus :: DList a -> DList a -> DList a Source #

MonadPlus IO

Since: base-4.9.0.0

Instance details

Defined in GHC.Base

Methods

mzero :: IO a Source #

mplus :: IO a -> IO a -> IO a Source #

MonadPlus Maybe

Since: base-2.1

Instance details

Defined in GHC.Base

Methods

mzero :: Maybe a Source #

mplus :: Maybe a -> Maybe a -> Maybe a Source #

MonadPlus []

Since: base-2.1

Instance details

Defined in GHC.Base

Methods

mzero :: [a] Source #

mplus :: [a] -> [a] -> [a] Source #

(ArrowApply a, ArrowPlus a) => MonadPlus (ArrowMonad a)

Since: base-4.6.0.0

Instance details

Defined in Control.Arrow

Methods

mzero :: ArrowMonad a a0 Source #

mplus :: ArrowMonad a a0 -> ArrowMonad a a0 -> ArrowMonad a a0 Source #

MonadPlus (Proxy :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in Data.Proxy

Methods

mzero :: Proxy a Source #

mplus :: Proxy a -> Proxy a -> Proxy a Source #

MonadPlus (U1 :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

mzero :: U1 a Source #

mplus :: U1 a -> U1 a -> U1 a Source #

MonadPlus m => MonadPlus (Kleisli m a)

Since: base-4.14.0.0

Instance details

Defined in Control.Arrow

Methods

mzero :: Kleisli m a a0 Source #

mplus :: Kleisli m a a0 -> Kleisli m a a0 -> Kleisli m a a0 Source #

MonadPlus f => MonadPlus (Ap f)

Since: base-4.12.0.0

Instance details

Defined in Data.Monoid

Methods

mzero :: Ap f a Source #

mplus :: Ap f a -> Ap f a -> Ap f a Source #

MonadPlus f => MonadPlus (Rec1 f)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

mzero :: Rec1 f a Source #

mplus :: Rec1 f a -> Rec1 f a -> Rec1 f a Source #

(MonadPlus f, MonadPlus g) => MonadPlus (Product f g)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Product

Methods

mzero :: Product f g a Source #

mplus :: Product f g a -> Product f g a -> Product f g a Source #

(MonadPlus f, MonadPlus g) => MonadPlus (f :*: g)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

mzero :: (f :*: g) a Source #

mplus :: (f :*: g) a -> (f :*: g) a -> (f :*: g) a Source #

MonadPlus f => MonadPlus (M1 i c f)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

mzero :: M1 i c f a Source #

mplus :: M1 i c f a -> M1 i c f a -> M1 i c f a Source #

class Applicative m => Monad (m :: Type -> Type) where Source #

The Monad class defines the basic operations over a monad, a concept from a branch of mathematics known as category theory. From the perspective of a Haskell programmer, however, it is best to think of a monad as an abstract datatype of actions. Haskell's do expressions provide a convenient syntax for writing monadic expressions.

Instances of Monad should satisfy the following:

Left identity
return a >>= k = k a
Right identity
m >>= return = m
Associativity
m >>= (\x -> k x >>= h) = (m >>= k) >>= h

Furthermore, the Monad and Applicative operations should relate as follows:

The above laws imply:

and that pure and (<*>) satisfy the applicative functor laws.

The instances of Monad for lists, Maybe and IO defined in the Prelude satisfy these laws.

Minimal complete definition

(>>=)

Methods

(>>=) :: m a -> (a -> m b) -> m b infixl 1 Source #

Sequentially compose two actions, passing any value produced by the first as an argument to the second.

'as >>= bs' can be understood as the do expression

do a <- as
   bs a

(>>) :: m a -> m b -> m b infixl 1 Source #

Sequentially compose two actions, discarding any value produced by the first, like sequencing operators (such as the semicolon) in imperative languages.

'as >> bs' can be understood as the do expression

do as
   bs

Instances

Instances details
Monad Complex

Since: base-4.9.0.0

Instance details

Defined in Data.Complex

Methods

(>>=) :: Complex a -> (a -> Complex b) -> Complex b Source #

(>>) :: Complex a -> Complex b -> Complex b Source #

return :: a -> Complex a Source #

Monad Identity

Since: base-4.8.0.0

Instance details

Defined in Data.Functor.Identity

Methods

(>>=) :: Identity a -> (a -> Identity b) -> Identity b Source #

(>>) :: Identity a -> Identity b -> Identity b Source #

return :: a -> Identity a Source #

Monad First

Since: base-4.8.0.0

Instance details

Defined in Data.Monoid

Methods

(>>=) :: First a -> (a -> First b) -> First b Source #

(>>) :: First a -> First b -> First b Source #

return :: a -> First a Source #

Monad Last

Since: base-4.8.0.0

Instance details

Defined in Data.Monoid

Methods

(>>=) :: Last a -> (a -> Last b) -> Last b Source #

(>>) :: Last a -> Last b -> Last b Source #

return :: a -> Last a Source #

Monad Down

Since: base-4.11.0.0

Instance details

Defined in Data.Ord

Methods

(>>=) :: Down a -> (a -> Down b) -> Down b Source #

(>>) :: Down a -> Down b -> Down b Source #

return :: a -> Down a Source #

Monad First

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Methods

(>>=) :: First a -> (a -> First b) -> First b Source #

(>>) :: First a -> First b -> First b Source #

return :: a -> First a Source #

Monad Last

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Methods

(>>=) :: Last a -> (a -> Last b) -> Last b Source #

(>>) :: Last a -> Last b -> Last b Source #

return :: a -> Last a Source #

Monad Max

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Methods

(>>=) :: Max a -> (a -> Max b) -> Max b Source #

(>>) :: Max a -> Max b -> Max b Source #

return :: a -> Max a Source #

Monad Min

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Methods

(>>=) :: Min a -> (a -> Min b) -> Min b Source #

(>>) :: Min a -> Min b -> Min b Source #

return :: a -> Min a Source #

Monad Par1

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

(>>=) :: Par1 a -> (a -> Par1 b) -> Par1 b Source #

(>>) :: Par1 a -> Par1 b -> Par1 b Source #

return :: a -> Par1 a Source #

Monad P

Since: base-2.1

Instance details

Defined in Text.ParserCombinators.ReadP

Methods

(>>=) :: P a -> (a -> P b) -> P b Source #

(>>) :: P a -> P b -> P b Source #

return :: a -> P a Source #

Monad ReadP

Since: base-2.1

Instance details

Defined in Text.ParserCombinators.ReadP

Methods

(>>=) :: ReadP a -> (a -> ReadP b) -> ReadP b Source #

(>>) :: ReadP a -> ReadP b -> ReadP b Source #

return :: a -> ReadP a Source #

Monad Seq 
Instance details

Defined in Data.Sequence.Internal

Methods

(>>=) :: Seq a -> (a -> Seq b) -> Seq b Source #

(>>) :: Seq a -> Seq b -> Seq b Source #

return :: a -> Seq a Source #

Monad DList 
Instance details

Defined in Data.DList.Internal

Methods

(>>=) :: DList a -> (a -> DList b) -> DList b Source #

(>>) :: DList a -> DList b -> DList b Source #

return :: a -> DList a Source #

Monad IO

Since: base-2.1

Instance details

Defined in GHC.Base

Methods

(>>=) :: IO a -> (a -> IO b) -> IO b Source #

(>>) :: IO a -> IO b -> IO b Source #

return :: a -> IO a Source #

Monad NonEmpty

Since: base-4.9.0.0

Instance details

Defined in GHC.Base

Methods

(>>=) :: NonEmpty a -> (a -> NonEmpty b) -> NonEmpty b Source #

(>>) :: NonEmpty a -> NonEmpty b -> NonEmpty b Source #

return :: a -> NonEmpty a Source #

Monad Maybe

Since: base-2.1

Instance details

Defined in GHC.Base

Methods

(>>=) :: Maybe a -> (a -> Maybe b) -> Maybe b Source #

(>>) :: Maybe a -> Maybe b -> Maybe b Source #

return :: a -> Maybe a Source #

Monad Solo

Since: base-4.15

Instance details

Defined in GHC.Base

Methods

(>>=) :: Solo a -> (a -> Solo b) -> Solo b Source #

(>>) :: Solo a -> Solo b -> Solo b Source #

return :: a -> Solo a Source #

Monad []

Since: base-2.1

Instance details

Defined in GHC.Base

Methods

(>>=) :: [a] -> (a -> [b]) -> [b] Source #

(>>) :: [a] -> [b] -> [b] Source #

return :: a -> [a] Source #

Monad m => Monad (WrappedMonad m)

Since: base-4.7.0.0

Instance details

Defined in Control.Applicative

Methods

(>>=) :: WrappedMonad m a -> (a -> WrappedMonad m b) -> WrappedMonad m b Source #

(>>) :: WrappedMonad m a -> WrappedMonad m b -> WrappedMonad m b Source #

return :: a -> WrappedMonad m a Source #

ArrowApply a => Monad (ArrowMonad a)

Since: base-2.1

Instance details

Defined in Control.Arrow

Methods

(>>=) :: ArrowMonad a a0 -> (a0 -> ArrowMonad a b) -> ArrowMonad a b Source #

(>>) :: ArrowMonad a a0 -> ArrowMonad a b -> ArrowMonad a b Source #

return :: a0 -> ArrowMonad a a0 Source #

Monad (Either e)

Since: base-4.4.0.0

Instance details

Defined in Data.Either

Methods

(>>=) :: Either e a -> (a -> Either e b) -> Either e b Source #

(>>) :: Either e a -> Either e b -> Either e b Source #

return :: a -> Either e a Source #

Monad (Proxy :: Type -> Type)

Since: base-4.7.0.0

Instance details

Defined in Data.Proxy

Methods

(>>=) :: Proxy a -> (a -> Proxy b) -> Proxy b Source #

(>>) :: Proxy a -> Proxy b -> Proxy b Source #

return :: a -> Proxy a Source #

Monad (U1 :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

(>>=) :: U1 a -> (a -> U1 b) -> U1 b Source #

(>>) :: U1 a -> U1 b -> U1 b Source #

return :: a -> U1 a Source #

Monoid a => Monad ((,) a)

Since: base-4.9.0.0

Instance details

Defined in GHC.Base

Methods

(>>=) :: (a, a0) -> (a0 -> (a, b)) -> (a, b) Source #

(>>) :: (a, a0) -> (a, b) -> (a, b) Source #

return :: a0 -> (a, a0) Source #

Monad m => Monad (Kleisli m a)

Since: base-4.14.0.0

Instance details

Defined in Control.Arrow

Methods

(>>=) :: Kleisli m a a0 -> (a0 -> Kleisli m a b) -> Kleisli m a b Source #

(>>) :: Kleisli m a a0 -> Kleisli m a b -> Kleisli m a b Source #

return :: a0 -> Kleisli m a a0 Source #

Monad f => Monad (Ap f)

Since: base-4.12.0.0

Instance details

Defined in Data.Monoid

Methods

(>>=) :: Ap f a -> (a -> Ap f b) -> Ap f b Source #

(>>) :: Ap f a -> Ap f b -> Ap f b Source #

return :: a -> Ap f a Source #

Monad f => Monad (Rec1 f)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

(>>=) :: Rec1 f a -> (a -> Rec1 f b) -> Rec1 f b Source #

(>>) :: Rec1 f a -> Rec1 f b -> Rec1 f b Source #

return :: a -> Rec1 f a Source #

(Applicative f, Monad f) => Monad (WhenMissing f x)

Equivalent to ReaderT k (ReaderT x (MaybeT f)).

Since: containers-0.5.9

Instance details

Defined in Data.IntMap.Internal

Methods

(>>=) :: WhenMissing f x a -> (a -> WhenMissing f x b) -> WhenMissing f x b Source #

(>>) :: WhenMissing f x a -> WhenMissing f x b -> WhenMissing f x b Source #

return :: a -> WhenMissing f x a Source #

(Monoid a, Monoid b) => Monad ((,,) a b)

Since: base-4.14.0.0

Instance details

Defined in GHC.Base

Methods

(>>=) :: (a, b, a0) -> (a0 -> (a, b, b0)) -> (a, b, b0) Source #

(>>) :: (a, b, a0) -> (a, b, b0) -> (a, b, b0) Source #

return :: a0 -> (a, b, a0) Source #

(Monad f, Monad g) => Monad (Product f g)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Product

Methods

(>>=) :: Product f g a -> (a -> Product f g b) -> Product f g b Source #

(>>) :: Product f g a -> Product f g b -> Product f g b Source #

return :: a -> Product f g a Source #

(Monad f, Monad g) => Monad (f :*: g)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

(>>=) :: (f :*: g) a -> (a -> (f :*: g) b) -> (f :*: g) b Source #

(>>) :: (f :*: g) a -> (f :*: g) b -> (f :*: g) b Source #

return :: a -> (f :*: g) a Source #

(Monad f, Applicative f) => Monad (WhenMatched f x y)

Equivalent to ReaderT Key (ReaderT x (ReaderT y (MaybeT f)))

Since: containers-0.5.9

Instance details

Defined in Data.IntMap.Internal

Methods

(>>=) :: WhenMatched f x y a -> (a -> WhenMatched f x y b) -> WhenMatched f x y b Source #

(>>) :: WhenMatched f x y a -> WhenMatched f x y b -> WhenMatched f x y b Source #

return :: a -> WhenMatched f x y a Source #

(Applicative f, Monad f) => Monad (WhenMissing f k x)

Equivalent to ReaderT k (ReaderT x (MaybeT f)) .

Since: containers-0.5.9

Instance details

Defined in Data.Map.Internal

Methods

(>>=) :: WhenMissing f k x a -> (a -> WhenMissing f k x b) -> WhenMissing f k x b Source #

(>>) :: WhenMissing f k x a -> WhenMissing f k x b -> WhenMissing f k x b Source #

return :: a -> WhenMissing f k x a Source #

(Monoid a, Monoid b, Monoid c) => Monad ((,,,) a b c)

Since: base-4.14.0.0

Instance details

Defined in GHC.Base

Methods

(>>=) :: (a, b, c, a0) -> (a0 -> (a, b, c, b0)) -> (a, b, c, b0) Source #

(>>) :: (a, b, c, a0) -> (a, b, c, b0) -> (a, b, c, b0) Source #

return :: a0 -> (a, b, c, a0) Source #

Monad ((->) r)

Since: base-2.1

Instance details

Defined in GHC.Base

Methods

(>>=) :: (r -> a) -> (a -> r -> b) -> r -> b Source #

(>>) :: (r -> a) -> (r -> b) -> r -> b Source #

return :: a -> r -> a Source #

Monad f => Monad (M1 i c f)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

(>>=) :: M1 i c f a -> (a -> M1 i c f b) -> M1 i c f b Source #

(>>) :: M1 i c f a -> M1 i c f b -> M1 i c f b Source #

return :: a -> M1 i c f a Source #

(Monad f, Applicative f) => Monad (WhenMatched f k x y)

Equivalent to ReaderT k (ReaderT x (ReaderT y (MaybeT f)))

Since: containers-0.5.9

Instance details

Defined in Data.Map.Internal

Methods

(>>=) :: WhenMatched f k x y a -> (a -> WhenMatched f k x y b) -> WhenMatched f k x y b Source #

(>>) :: WhenMatched f k x y a -> WhenMatched f k x y b -> WhenMatched f k x y b Source #

return :: a -> WhenMatched f k x y a Source #

forever :: Applicative f => f a -> f b Source #

Repeat an action indefinitely.

Examples

Expand

A common use of forever is to process input from network sockets, Handles, and channels (e.g. MVar and Chan).

For example, here is how we might implement an echo server, using forever both to listen for client connections on a network socket and to echo client input on client connection handles:

echoServer :: Socket -> IO ()
echoServer socket = forever $ do
  client <- accept socket
  forkFinally (echo client) (\_ -> hClose client)
  where
    echo :: Handle -> IO ()
    echo client = forever $
      hGetLine client >>= hPutStrLn client

Note that "forever" isn't necessarily non-terminating. If the action is in a MonadPlus and short-circuits after some number of iterations. then forever actually returns mzero, effectively short-circuiting its caller.

guard :: Alternative f => Bool -> f () Source #

Conditional failure of Alternative computations. Defined by

guard True  = pure ()
guard False = empty

Examples

Expand

Common uses of guard include conditionally signaling an error in an error monad and conditionally rejecting the current choice in an Alternative-based parser.

As an example of signaling an error in the error monad Maybe, consider a safe division function safeDiv x y that returns Nothing when the denominator y is zero and Just (x `div` y) otherwise. For example:

>>> safeDiv 4 0
Nothing
>>> safeDiv 4 2
Just 2

A definition of safeDiv using guards, but not guard:

safeDiv :: Int -> Int -> Maybe Int
safeDiv x y | y /= 0    = Just (x `div` y)
            | otherwise = Nothing

A definition of safeDiv using guard and Monad do-notation:

safeDiv :: Int -> Int -> Maybe Int
safeDiv x y = do
  guard (y /= 0)
  return (x `div` y)

join :: Monad m => m (m a) -> m a Source #

The join function is the conventional monad join operator. It is used to remove one level of monadic structure, projecting its bound argument into the outer level.

'join bss' can be understood as the do expression

do bs <- bss
   bs

Examples

Expand

A common use of join is to run an IO computation returned from an STM transaction, since STM transactions can't perform IO directly. Recall that

atomically :: STM a -> IO a

is used to run STM transactions atomically. So, by specializing the types of atomically and join to

atomically :: STM (IO b) -> IO (IO b)
join       :: IO (IO b)  -> IO b

we can compose them as

join . atomically :: STM (IO b) -> IO b

to run an STM transaction and the IO action it returns.

(=<<) :: Monad m => (a -> m b) -> m a -> m b infixr 1 Source #

Same as >>=, but with the arguments interchanged.

when :: Applicative f => Bool -> f () -> f () Source #

Conditional execution of Applicative expressions. For example,

when debug (putStrLn "Debugging")

will output the string Debugging if the Boolean value debug is True, and otherwise do nothing.

filterM :: Applicative m => (a -> m Bool) -> [a] -> m [a] Source #

This generalizes the list-based filter function.

(>=>) :: Monad m => (a -> m b) -> (b -> m c) -> a -> m c infixr 1 Source #

Left-to-right composition of Kleisli arrows.

'(bs >=> cs) a' can be understood as the do expression

do b <- bs a
   cs b

(<=<) :: Monad m => (b -> m c) -> (a -> m b) -> a -> m c infixr 1 Source #

Right-to-left composition of Kleisli arrows. (>=>), with the arguments flipped.

Note how this operator resembles function composition (.):

(.)   ::            (b ->   c) -> (a ->   b) -> a ->   c
(<=<) :: Monad m => (b -> m c) -> (a -> m b) -> a -> m c

zipWithM :: Applicative m => (a -> b -> m c) -> [a] -> [b] -> m [c] Source #

The zipWithM function generalizes zipWith to arbitrary applicative functors.

zipWithM_ :: Applicative m => (a -> b -> m c) -> [a] -> [b] -> m () Source #

zipWithM_ is the extension of zipWithM which ignores the final result.

replicateM :: Applicative m => Int -> m a -> m [a] Source #

replicateM n act performs the action act n times, and then returns the list of results:

Examples

Expand
>>> import Control.Monad.State
>>> runState (replicateM 3 $ state $ \s -> (s, s + 1)) 1
([1,2,3],4)

replicateM_ :: Applicative m => Int -> m a -> m () Source #

Like replicateM, but discards the result.

Examples

Expand
>>> replicateM_ 3 (putStrLn "a")
a
a
a

unless :: Applicative f => Bool -> f () -> f () Source #

The reverse of when.

(<$!>) :: Monad m => (a -> b) -> m a -> m b infixl 4 Source #

Strict version of <$>.

Since: base-4.8.0.0

mfilter :: MonadPlus m => (a -> Bool) -> m a -> m a Source #

Direct MonadPlus equivalent of filter.

Examples

Expand

The filter function is just mfilter specialized to the list monad:

filter = ( mfilter :: (a -> Bool) -> [a] -> [a] )

An example using mfilter with the Maybe monad:

>>> mfilter odd (Just 1)
Just 1
>>> mfilter odd (Just 2)
Nothing

class Monad m => MonadFail (m :: Type -> Type) where Source #

When a value is bound in do-notation, the pattern on the left hand side of <- might not match. In this case, this class provides a function to recover.

A Monad without a MonadFail instance may only be used in conjunction with pattern that always match, such as newtypes, tuples, data types with only a single data constructor, and irrefutable patterns (~pat).

Instances of MonadFail should satisfy the following law: fail s should be a left zero for >>=,

fail s >>= f  =  fail s

If your Monad is also MonadPlus, a popular definition is

fail _ = mzero

Since: base-4.9.0.0

Methods

fail :: String -> m a Source #

Instances

Instances details
MonadFail P

Since: base-4.9.0.0

Instance details

Defined in Text.ParserCombinators.ReadP

Methods

fail :: String -> P a Source #

MonadFail ReadP

Since: base-4.9.0.0

Instance details

Defined in Text.ParserCombinators.ReadP

Methods

fail :: String -> ReadP a Source #

MonadFail DList 
Instance details

Defined in Data.DList.Internal

Methods

fail :: String -> DList a Source #

MonadFail IO

Since: base-4.9.0.0

Instance details

Defined in Control.Monad.Fail

Methods

fail :: String -> IO a Source #

MonadFail Maybe

Since: base-4.9.0.0

Instance details

Defined in Control.Monad.Fail

Methods

fail :: String -> Maybe a Source #

MonadFail []

Since: base-4.9.0.0

Instance details

Defined in Control.Monad.Fail

Methods

fail :: String -> [a] Source #

MonadFail f => MonadFail (Ap f)

Since: base-4.12.0.0

Instance details

Defined in Data.Monoid

Methods

fail :: String -> Ap f a Source #

class Bifunctor (p :: Type -> Type -> Type) where Source #

A bifunctor is a type constructor that takes two type arguments and is a functor in both arguments. That is, unlike with Functor, a type constructor such as Either does not need to be partially applied for a Bifunctor instance, and the methods in this class permit mapping functions over the Left value or the Right value, or both at the same time.

Formally, the class Bifunctor represents a bifunctor from Hask -> Hask.

Intuitively it is a bifunctor where both the first and second arguments are covariant.

You can define a Bifunctor by either defining bimap or by defining both first and second.

If you supply bimap, you should ensure that:

bimap id idid

If you supply first and second, ensure:

first idid
second idid

If you supply both, you should also ensure:

bimap f g ≡ first f . second g

These ensure by parametricity:

bimap  (f . g) (h . i) ≡ bimap f h . bimap g i
first  (f . g) ≡ first  f . first  g
second (f . g) ≡ second f . second g

Since: base-4.8.0.0

Minimal complete definition

bimap | first, second

Methods

bimap :: (a -> b) -> (c -> d) -> p a c -> p b d Source #

Map over both arguments at the same time.

bimap f g ≡ first f . second g

Examples

Expand
>>> bimap toUpper (+1) ('j', 3)
('J',4)
>>> bimap toUpper (+1) (Left 'j')
Left 'J'
>>> bimap toUpper (+1) (Right 3)
Right 4

first :: (a -> b) -> p a c -> p b c Source #

Map covariantly over the first argument.

first f ≡ bimap f id

Examples

Expand
>>> first toUpper ('j', 3)
('J',3)
>>> first toUpper (Left 'j')
Left 'J'

second :: (b -> c) -> p a b -> p a c Source #

Map covariantly over the second argument.

secondbimap id

Examples

Expand
>>> second (+1) ('j', 3)
('j',4)
>>> second (+1) (Right 3)
Right 4

Instances

Instances details
Bifunctor Either

Since: base-4.8.0.0

Instance details

Defined in Data.Bifunctor

Methods

bimap :: (a -> b) -> (c -> d) -> Either a c -> Either b d Source #

first :: (a -> b) -> Either a c -> Either b c Source #

second :: (b -> c) -> Either a b -> Either a c Source #

Bifunctor Arg

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Methods

bimap :: (a -> b) -> (c -> d) -> Arg a c -> Arg b d Source #

first :: (a -> b) -> Arg a c -> Arg b c Source #

second :: (b -> c) -> Arg a b -> Arg a c Source #

Bifunctor (,)

Since: base-4.8.0.0

Instance details

Defined in Data.Bifunctor

Methods

bimap :: (a -> b) -> (c -> d) -> (a, c) -> (b, d) Source #

first :: (a -> b) -> (a, c) -> (b, c) Source #

second :: (b -> c) -> (a, b) -> (a, c) Source #

Bifunctor (Const :: Type -> Type -> Type)

Since: base-4.8.0.0

Instance details

Defined in Data.Bifunctor

Methods

bimap :: (a -> b) -> (c -> d) -> Const a c -> Const b d Source #

first :: (a -> b) -> Const a c -> Const b c Source #

second :: (b -> c) -> Const a b -> Const a c Source #

Bifunctor ((,,) x1)

Since: base-4.8.0.0

Instance details

Defined in Data.Bifunctor

Methods

bimap :: (a -> b) -> (c -> d) -> (x1, a, c) -> (x1, b, d) Source #

first :: (a -> b) -> (x1, a, c) -> (x1, b, c) Source #

second :: (b -> c) -> (x1, a, b) -> (x1, a, c) Source #

Bifunctor (K1 i :: Type -> Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in Data.Bifunctor

Methods

bimap :: (a -> b) -> (c -> d) -> K1 i a c -> K1 i b d Source #

first :: (a -> b) -> K1 i a c -> K1 i b c Source #

second :: (b -> c) -> K1 i a b -> K1 i a c Source #

Bifunctor ((,,,) x1 x2)

Since: base-4.8.0.0

Instance details

Defined in Data.Bifunctor

Methods

bimap :: (a -> b) -> (c -> d) -> (x1, x2, a, c) -> (x1, x2, b, d) Source #

first :: (a -> b) -> (x1, x2, a, c) -> (x1, x2, b, c) Source #

second :: (b -> c) -> (x1, x2, a, b) -> (x1, x2, a, c) Source #

Bifunctor ((,,,,) x1 x2 x3)

Since: base-4.8.0.0

Instance details

Defined in Data.Bifunctor

Methods

bimap :: (a -> b) -> (c -> d) -> (x1, x2, x3, a, c) -> (x1, x2, x3, b, d) Source #

first :: (a -> b) -> (x1, x2, x3, a, c) -> (x1, x2, x3, b, c) Source #

second :: (b -> c) -> (x1, x2, x3, a, b) -> (x1, x2, x3, a, c) Source #

Bifunctor ((,,,,,) x1 x2 x3 x4)

Since: base-4.8.0.0

Instance details

Defined in Data.Bifunctor

Methods

bimap :: (a -> b) -> (c -> d) -> (x1, x2, x3, x4, a, c) -> (x1, x2, x3, x4, b, d) Source #

first :: (a -> b) -> (x1, x2, x3, x4, a, c) -> (x1, x2, x3, x4, b, c) Source #

second :: (b -> c) -> (x1, x2, x3, x4, a, b) -> (x1, x2, x3, x4, a, c) Source #

Bifunctor ((,,,,,,) x1 x2 x3 x4 x5)

Since: base-4.8.0.0

Instance details

Defined in Data.Bifunctor

Methods

bimap :: (a -> b) -> (c -> d) -> (x1, x2, x3, x4, x5, a, c) -> (x1, x2, x3, x4, x5, b, d) Source #

first :: (a -> b) -> (x1, x2, x3, x4, x5, a, c) -> (x1, x2, x3, x4, x5, b, c) Source #

second :: (b -> c) -> (x1, x2, x3, x4, x5, a, b) -> (x1, x2, x3, x4, x5, a, c) Source #

xor :: Bits a => a -> a -> a infixl 6 Source #

Bitwise "xor"

toIntegralSized :: (Integral a, Integral b, Bits a, Bits b) => a -> Maybe b Source #

Attempt to convert an Integral type a to an Integral type b using the size of the types as measured by Bits methods.

A simpler version of this function is:

toIntegral :: (Integral a, Integral b) => a -> Maybe b
toIntegral x
  | toInteger x == toInteger y = Just y
  | otherwise                  = Nothing
  where
    y = fromIntegral x

This version requires going through Integer, which can be inefficient. However, toIntegralSized is optimized to allow GHC to statically determine the relative type sizes (as measured by bitSizeMaybe and isSigned) and avoid going through Integer for many types. (The implementation uses fromIntegral, which is itself optimized with rules for base types but may go through Integer for some type pairs.)

Since: base-4.8.0.0

data Bool Source #

Constructors

False 
True 

Instances

Instances details
Bits Bool

Interpret Bool as 1-bit bit-field

Since: base-4.7.0.0

Instance details

Defined in GHC.Bits

FiniteBits Bool

Since: base-4.7.0.0

Instance details

Defined in GHC.Bits

Bounded Bool

Since: base-2.1

Instance details

Defined in GHC.Enum

Enum Bool

Since: base-2.1

Instance details

Defined in GHC.Enum

Generic Bool 
Instance details

Defined in GHC.Generics

Associated Types

type Rep Bool :: Type -> Type Source #

Methods

from :: Bool -> Rep Bool x Source #

to :: Rep Bool x -> Bool Source #

SingKind Bool

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Associated Types

type DemoteRep Bool

Methods

fromSing :: forall (a :: Bool). Sing a -> DemoteRep Bool

Read Bool

Since: base-2.1

Instance details

Defined in GHC.Read

Show Bool

Since: base-2.1

Instance details

Defined in GHC.Show

Eq Bool 
Instance details

Defined in GHC.Classes

Methods

(==) :: Bool -> Bool -> Bool Source #

(/=) :: Bool -> Bool -> Bool Source #

Ord Bool 
Instance details

Defined in GHC.Classes

SingI 'False

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

sing :: Sing 'False

SingI 'True

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

sing :: Sing 'True

type DemoteRep Bool 
Instance details

Defined in GHC.Generics

type DemoteRep Bool = Bool
type Rep Bool

Since: base-4.6.0.0

Instance details

Defined in GHC.Generics

type Rep Bool = D1 ('MetaData "Bool" "GHC.Types" "ghc-prim" 'False) (C1 ('MetaCons "False" 'PrefixI 'False) (U1 :: Type -> Type) :+: C1 ('MetaCons "True" 'PrefixI 'False) (U1 :: Type -> Type))
data Sing (a :: Bool) 
Instance details

Defined in GHC.Generics

data Sing (a :: Bool) where

otherwise :: Bool Source #

otherwise is defined as the value True. It helps to make guards more readable. eg.

 f x | x < 0     = ...
     | otherwise = ...

(&&) :: Bool -> Bool -> Bool infixr 3 Source #

Boolean "and", lazy in the second argument

(||) :: Bool -> Bool -> Bool infixr 2 Source #

Boolean "or", lazy in the second argument

not :: Bool -> Bool Source #

Boolean "not"

bool :: a -> a -> Bool -> a Source #

Case analysis for the Bool type. bool x y p evaluates to x when p is False, and evaluates to y when p is True.

This is equivalent to if p then y else x; that is, one can think of it as an if-then-else construct with its arguments reordered.

Examples

Expand

Basic usage:

>>> bool "foo" "bar" True
"bar"
>>> bool "foo" "bar" False
"foo"

Confirm that bool x y p and if p then y else x are equivalent:

>>> let p = True; x = "bar"; y = "foo"
>>> bool x y p == if p then y else x
True
>>> let p = False
>>> bool x y p == if p then y else x
True

Since: base-4.7.0.0

data Char Source #

The character type Char is an enumeration whose values represent Unicode (or equivalently ISO/IEC 10646) code points (i.e. characters, see http://www.unicode.org/ for details). This set extends the ISO 8859-1 (Latin-1) character set (the first 256 characters), which is itself an extension of the ASCII character set (the first 128 characters). A character literal in Haskell has type Char.

To convert a Char to or from the corresponding Int value defined by Unicode, use toEnum and fromEnum from the Enum class respectively (or equivalently ord and chr).

Instances

Instances details
Bounded Char

Since: base-2.1

Instance details

Defined in GHC.Enum

Enum Char

Since: base-2.1

Instance details

Defined in GHC.Enum

Read Char

Since: base-2.1

Instance details

Defined in GHC.Read

Show Char

Since: base-2.1

Instance details

Defined in GHC.Show

Eq Char 
Instance details

Defined in GHC.Classes

Methods

(==) :: Char -> Char -> Bool Source #

(/=) :: Char -> Char -> Bool Source #

Ord Char 
Instance details

Defined in GHC.Classes

ToLText String Source # 
Instance details

Defined in Incipit.String.Conversion

Methods

toLText :: String -> LText Source #

ToString String Source # 
Instance details

Defined in Incipit.String.Conversion

ToText String Source # 
Instance details

Defined in Incipit.String.Conversion

Methods

toText :: String -> Text Source #

ConvertUtf8 String ByteString Source # 
Instance details

Defined in Incipit.String.Conversion

ConvertUtf8 String ShortByteString Source #

Since: 0.6.0.0

Instance details

Defined in Incipit.String.Conversion

ConvertUtf8 String LByteString Source #

Converting String to ByteString might be a slow operation. Consider using lazy bytestring at first place.

Instance details

Defined in Incipit.String.Conversion

Generic1 (URec Char :: k -> Type) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep1 (URec Char) :: k -> Type Source #

Methods

from1 :: forall (a :: k0). URec Char a -> Rep1 (URec Char) a Source #

to1 :: forall (a :: k0). Rep1 (URec Char) a -> URec Char a Source #

Foldable (UChar :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in Data.Foldable

Methods

fold :: Monoid m => UChar m -> m Source #

foldMap :: Monoid m => (a -> m) -> UChar a -> m Source #

foldMap' :: Monoid m => (a -> m) -> UChar a -> m Source #

foldr :: (a -> b -> b) -> b -> UChar a -> b Source #

foldr' :: (a -> b -> b) -> b -> UChar a -> b Source #

foldl :: (b -> a -> b) -> b -> UChar a -> b Source #

foldl' :: (b -> a -> b) -> b -> UChar a -> b Source #

foldr1 :: (a -> a -> a) -> UChar a -> a Source #

foldl1 :: (a -> a -> a) -> UChar a -> a Source #

toList :: UChar a -> [a] Source #

null :: UChar a -> Bool Source #

length :: UChar a -> Int Source #

elem :: Eq a => a -> UChar a -> Bool Source #

maximum :: Ord a => UChar a -> a Source #

minimum :: Ord a => UChar a -> a Source #

sum :: Num a => UChar a -> a Source #

product :: Num a => UChar a -> a Source #

Traversable (UChar :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in Data.Traversable

Methods

traverse :: Applicative f => (a -> f b) -> UChar a -> f (UChar b) Source #

sequenceA :: Applicative f => UChar (f a) -> f (UChar a) Source #

mapM :: Monad m => (a -> m b) -> UChar a -> m (UChar b) Source #

sequence :: Monad m => UChar (m a) -> m (UChar a) Source #

Functor (URec Char :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

fmap :: (a -> b) -> URec Char a -> URec Char b Source #

(<$) :: a -> URec Char b -> URec Char a Source #

Generic (URec Char p) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (URec Char p) :: Type -> Type Source #

Methods

from :: URec Char p -> Rep (URec Char p) x Source #

to :: Rep (URec Char p) x -> URec Char p Source #

Show (URec Char p)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Eq (URec Char p)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

(==) :: URec Char p -> URec Char p -> Bool Source #

(/=) :: URec Char p -> URec Char p -> Bool Source #

Ord (URec Char p)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

compare :: URec Char p -> URec Char p -> Ordering Source #

(<) :: URec Char p -> URec Char p -> Bool Source #

(<=) :: URec Char p -> URec Char p -> Bool Source #

(>) :: URec Char p -> URec Char p -> Bool Source #

(>=) :: URec Char p -> URec Char p -> Bool Source #

max :: URec Char p -> URec Char p -> URec Char p Source #

min :: URec Char p -> URec Char p -> URec Char p Source #

data URec Char (p :: k)

Used for marking occurrences of Char#

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

data URec Char (p :: k) = UChar {}
type Compare (a :: Char) (b :: Char) 
Instance details

Defined in Data.Type.Ord

type Compare (a :: Char) (b :: Char) = CmpChar a b
type Rep1 (URec Char :: k -> Type)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

type Rep1 (URec Char :: k -> Type) = D1 ('MetaData "URec" "GHC.Generics" "base" 'False) (C1 ('MetaCons "UChar" 'PrefixI 'True) (S1 ('MetaSel ('Just "uChar#") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (UChar :: k -> Type)))
type Rep (URec Char p)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

type Rep (URec Char p) = D1 ('MetaData "URec" "GHC.Generics" "base" 'False) (C1 ('MetaCons "UChar" 'PrefixI 'True) (S1 ('MetaSel ('Just "uChar#") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (UChar :: Type -> Type)))

chr :: Int -> Char Source #

The toEnum method restricted to the type Char.

class a ~R# b => Coercible (a :: k) (b :: k) Source #

Coercible is a two-parameter class that has instances for types a and b if the compiler can infer that they have the same representation. This class does not have regular instances; instead they are created on-the-fly during type-checking. Trying to manually declare an instance of Coercible is an error.

Nevertheless one can pretend that the following three kinds of instances exist. First, as a trivial base-case:

instance Coercible a a

Furthermore, for every type constructor there is an instance that allows to coerce under the type constructor. For example, let D be a prototypical type constructor (data or newtype) with three type arguments, which have roles nominal, representational resp. phantom. Then there is an instance of the form

instance Coercible b b' => Coercible (D a b c) (D a b' c')

Note that the nominal type arguments are equal, the representational type arguments can differ, but need to have a Coercible instance themself, and the phantom type arguments can be changed arbitrarily.

The third kind of instance exists for every newtype NT = MkNT T and comes in two variants, namely

instance Coercible a T => Coercible a NT
instance Coercible T b => Coercible NT b

This instance is only usable if the constructor MkNT is in scope.

If, as a library author of a type constructor like Set a, you want to prevent a user of your module to write coerce :: Set T -> Set NT, you need to set the role of Set's type parameter to nominal, by writing

type role Set nominal

For more details about this feature, please refer to Safe Coercions by Joachim Breitner, Richard A. Eisenberg, Simon Peyton Jones and Stephanie Weirich.

Since: ghc-prim-0.4.0

coerce :: forall {k :: RuntimeRep} (a :: TYPE k) (b :: TYPE k). Coercible a b => a -> b Source #

The function coerce allows you to safely convert between values of types that have the same representation with no run-time overhead. In the simplest case you can use it instead of a newtype constructor, to go from the newtype's concrete type to the abstract type. But it also works in more complicated settings, e.g. converting a list of newtypes to a list of concrete types.

This function is representation-polymorphic, but the RuntimeRep type argument is marked as Inferred, meaning that it is not available for visible type application. This means the typechecker will accept coerce @Int @Age 42.

class Eq a where Source #

The Eq class defines equality (==) and inequality (/=). All the basic datatypes exported by the Prelude are instances of Eq, and Eq may be derived for any datatype whose constituents are also instances of Eq.

The Haskell Report defines no laws for Eq. However, instances are encouraged to follow these properties:

Reflexivity
x == x = True
Symmetry
x == y = y == x
Transitivity
if x == y && y == z = True, then x == z = True
Extensionality
if x == y = True and f is a function whose return type is an instance of Eq, then f x == f y = True
Negation
x /= y = not (x == y)

Minimal complete definition: either == or /=.

Minimal complete definition

(==) | (/=)

Methods

(==) :: a -> a -> Bool infix 4 Source #

(/=) :: a -> a -> Bool infix 4 Source #

Instances

Instances details
Eq SomeTypeRep 
Instance details

Defined in Data.Typeable.Internal

Eq Void

Since: base-4.8.0.0

Instance details

Defined in Data.Void

Methods

(==) :: Void -> Void -> Bool Source #

(/=) :: Void -> Void -> Bool Source #

Eq ArithException

Since: base-3.0

Instance details

Defined in GHC.Exception.Type

Eq Associativity

Since: base-4.6.0.0

Instance details

Defined in GHC.Generics

Eq DecidedStrictness

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Eq Fixity

Since: base-4.6.0.0

Instance details

Defined in GHC.Generics

Eq SourceStrictness

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Eq SourceUnpackedness

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Eq MaskingState

Since: base-4.3.0.0

Instance details

Defined in GHC.IO

Eq Int16

Since: base-2.1

Instance details

Defined in GHC.Int

Methods

(==) :: Int16 -> Int16 -> Bool Source #

(/=) :: Int16 -> Int16 -> Bool Source #

Eq Int32

Since: base-2.1

Instance details

Defined in GHC.Int

Methods

(==) :: Int32 -> Int32 -> Bool Source #

(/=) :: Int32 -> Int32 -> Bool Source #

Eq Int64

Since: base-2.1

Instance details

Defined in GHC.Int

Methods

(==) :: Int64 -> Int64 -> Bool Source #

(/=) :: Int64 -> Int64 -> Bool Source #

Eq Int8

Since: base-2.1

Instance details

Defined in GHC.Int

Methods

(==) :: Int8 -> Int8 -> Bool Source #

(/=) :: Int8 -> Int8 -> Bool Source #

Eq SrcLoc

Since: base-4.9.0.0

Instance details

Defined in GHC.Stack.Types

Eq SomeChar 
Instance details

Defined in GHC.TypeLits

Eq SomeSymbol

Since: base-4.7.0.0

Instance details

Defined in GHC.TypeLits

Eq SomeNat

Since: base-4.7.0.0

Instance details

Defined in GHC.TypeNats

Eq Word16

Since: base-2.1

Instance details

Defined in GHC.Word

Eq Word32

Since: base-2.1

Instance details

Defined in GHC.Word

Eq Word64

Since: base-2.1

Instance details

Defined in GHC.Word

Eq Word8

Since: base-2.1

Instance details

Defined in GHC.Word

Methods

(==) :: Word8 -> Word8 -> Bool Source #

(/=) :: Word8 -> Word8 -> Bool Source #

Eq ByteString 
Instance details

Defined in Data.ByteString.Internal.Type

Eq ByteString 
Instance details

Defined in Data.ByteString.Lazy.Internal

Eq ShortByteString 
Instance details

Defined in Data.ByteString.Short.Internal

Eq IntSet 
Instance details

Defined in Data.IntSet.Internal

Eq BigNat 
Instance details

Defined in GHC.Num.BigNat

Eq Module 
Instance details

Defined in GHC.Classes

Eq Ordering 
Instance details

Defined in GHC.Classes

Eq TrName 
Instance details

Defined in GHC.Classes

Eq TyCon 
Instance details

Defined in GHC.Classes

Methods

(==) :: TyCon -> TyCon -> Bool Source #

(/=) :: TyCon -> TyCon -> Bool Source #

Eq UnicodeException 
Instance details

Defined in Data.Text.Encoding.Error

Eq Integer 
Instance details

Defined in GHC.Num.Integer

Eq Natural 
Instance details

Defined in GHC.Num.Natural

Eq () 
Instance details

Defined in GHC.Classes

Methods

(==) :: () -> () -> Bool Source #

(/=) :: () -> () -> Bool Source #

Eq Bool 
Instance details

Defined in GHC.Classes

Methods

(==) :: Bool -> Bool -> Bool Source #

(/=) :: Bool -> Bool -> Bool Source #

Eq Char 
Instance details

Defined in GHC.Classes

Methods

(==) :: Char -> Char -> Bool Source #

(/=) :: Char -> Char -> Bool Source #

Eq Double

Note that due to the presence of NaN, Double's Eq instance does not satisfy reflexivity.

>>> 0/0 == (0/0 :: Double)
False

Also note that Double's Eq instance does not satisfy substitutivity:

>>> 0 == (-0 :: Double)
True
>>> recip 0 == recip (-0 :: Double)
False
Instance details

Defined in GHC.Classes

Eq Float

Note that due to the presence of NaN, Float's Eq instance does not satisfy reflexivity.

>>> 0/0 == (0/0 :: Float)
False

Also note that Float's Eq instance does not satisfy extensionality:

>>> 0 == (-0 :: Float)
True
>>> recip 0 == recip (-0 :: Float)
False
Instance details

Defined in GHC.Classes

Methods

(==) :: Float -> Float -> Bool Source #

(/=) :: Float -> Float -> Bool Source #

Eq Int 
Instance details

Defined in GHC.Classes

Methods

(==) :: Int -> Int -> Bool Source #

(/=) :: Int -> Int -> Bool Source #

Eq Word 
Instance details

Defined in GHC.Classes

Methods

(==) :: Word -> Word -> Bool Source #

(/=) :: Word -> Word -> Bool Source #

Eq a => Eq (ZipList a)

Since: base-4.7.0.0

Instance details

Defined in Control.Applicative

Methods

(==) :: ZipList a -> ZipList a -> Bool Source #

(/=) :: ZipList a -> ZipList a -> Bool Source #

Eq a => Eq (And a)

Since: base-4.16

Instance details

Defined in Data.Bits

Methods

(==) :: And a -> And a -> Bool Source #

(/=) :: And a -> And a -> Bool Source #

Eq a => Eq (Iff a)

Since: base-4.16

Instance details

Defined in Data.Bits

Methods

(==) :: Iff a -> Iff a -> Bool Source #

(/=) :: Iff a -> Iff a -> Bool Source #

Eq a => Eq (Ior a)

Since: base-4.16

Instance details

Defined in Data.Bits

Methods

(==) :: Ior a -> Ior a -> Bool Source #

(/=) :: Ior a -> Ior a -> Bool Source #

Eq a => Eq (Xor a)

Since: base-4.16

Instance details

Defined in Data.Bits

Methods

(==) :: Xor a -> Xor a -> Bool Source #

(/=) :: Xor a -> Xor a -> Bool Source #

Eq a => Eq (Complex a)

Since: base-2.1

Instance details

Defined in Data.Complex

Methods

(==) :: Complex a -> Complex a -> Bool Source #

(/=) :: Complex a -> Complex a -> Bool Source #

Eq a => Eq (Identity a)

Since: base-4.8.0.0

Instance details

Defined in Data.Functor.Identity

Methods

(==) :: Identity a -> Identity a -> Bool Source #

(/=) :: Identity a -> Identity a -> Bool Source #

Eq a => Eq (First a)

Since: base-2.1

Instance details

Defined in Data.Monoid

Methods

(==) :: First a -> First a -> Bool Source #

(/=) :: First a -> First a -> Bool Source #

Eq a => Eq (Last a)

Since: base-2.1

Instance details

Defined in Data.Monoid

Methods

(==) :: Last a -> Last a -> Bool Source #

(/=) :: Last a -> Last a -> Bool Source #

Eq a => Eq (Down a)

Since: base-4.6.0.0

Instance details

Defined in Data.Ord

Methods

(==) :: Down a -> Down a -> Bool Source #

(/=) :: Down a -> Down a -> Bool Source #

Eq a => Eq (First a)

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Methods

(==) :: First a -> First a -> Bool Source #

(/=) :: First a -> First a -> Bool Source #

Eq a => Eq (Last a)

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Methods

(==) :: Last a -> Last a -> Bool Source #

(/=) :: Last a -> Last a -> Bool Source #

Eq a => Eq (Max a)

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Methods

(==) :: Max a -> Max a -> Bool Source #

(/=) :: Max a -> Max a -> Bool Source #

Eq a => Eq (Min a)

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Methods

(==) :: Min a -> Min a -> Bool Source #

(/=) :: Min a -> Min a -> Bool Source #

Eq m => Eq (WrappedMonoid m)

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Eq p => Eq (Par1 p)

Since: base-4.7.0.0

Instance details

Defined in GHC.Generics

Methods

(==) :: Par1 p -> Par1 p -> Bool Source #

(/=) :: Par1 p -> Par1 p -> Bool Source #

Eq (MVar a)

Since: base-4.1.0.0

Instance details

Defined in GHC.MVar

Methods

(==) :: MVar a -> MVar a -> Bool Source #

(/=) :: MVar a -> MVar a -> Bool Source #

Eq a => Eq (Ratio a)

Since: base-2.1

Instance details

Defined in GHC.Real

Methods

(==) :: Ratio a -> Ratio a -> Bool Source #

(/=) :: Ratio a -> Ratio a -> Bool Source #

Eq a => Eq (IntMap a) 
Instance details

Defined in Data.IntMap.Internal

Methods

(==) :: IntMap a -> IntMap a -> Bool Source #

(/=) :: IntMap a -> IntMap a -> Bool Source #

Eq a => Eq (Seq a) 
Instance details

Defined in Data.Sequence.Internal

Methods

(==) :: Seq a -> Seq a -> Bool Source #

(/=) :: Seq a -> Seq a -> Bool Source #

Eq a => Eq (ViewL a) 
Instance details

Defined in Data.Sequence.Internal

Methods

(==) :: ViewL a -> ViewL a -> Bool Source #

(/=) :: ViewL a -> ViewL a -> Bool Source #

Eq a => Eq (ViewR a) 
Instance details

Defined in Data.Sequence.Internal

Methods

(==) :: ViewR a -> ViewR a -> Bool Source #

(/=) :: ViewR a -> ViewR a -> Bool Source #

Eq a => Eq (Intersection a) 
Instance details

Defined in Data.Set.Internal

Eq a => Eq (Set a) 
Instance details

Defined in Data.Set.Internal

Methods

(==) :: Set a -> Set a -> Bool Source #

(/=) :: Set a -> Set a -> Bool Source #

Eq a => Eq (DList a) 
Instance details

Defined in Data.DList.Internal

Methods

(==) :: DList a -> DList a -> Bool Source #

(/=) :: DList a -> DList a -> Bool Source #

Eq a => Eq (NonEmpty a)

Since: base-4.9.0.0

Instance details

Defined in GHC.Base

Methods

(==) :: NonEmpty a -> NonEmpty a -> Bool Source #

(/=) :: NonEmpty a -> NonEmpty a -> Bool Source #

Eq a => Eq (Maybe a)

Since: base-2.1

Instance details

Defined in GHC.Maybe

Methods

(==) :: Maybe a -> Maybe a -> Bool Source #

(/=) :: Maybe a -> Maybe a -> Bool Source #

Eq a => Eq (a) 
Instance details

Defined in GHC.Classes

Methods

(==) :: (a) -> (a) -> Bool Source #

(/=) :: (a) -> (a) -> Bool Source #

Eq a => Eq [a] 
Instance details

Defined in GHC.Classes

Methods

(==) :: [a] -> [a] -> Bool Source #

(/=) :: [a] -> [a] -> Bool Source #

(Eq a, Eq b) => Eq (Either a b)

Since: base-2.1

Instance details

Defined in Data.Either

Methods

(==) :: Either a b -> Either a b -> Bool Source #

(/=) :: Either a b -> Either a b -> Bool Source #

Eq (Fixed a)

Since: base-2.1

Instance details

Defined in Data.Fixed

Methods

(==) :: Fixed a -> Fixed a -> Bool Source #

(/=) :: Fixed a -> Fixed a -> Bool Source #

Eq (Proxy s)

Since: base-4.7.0.0

Instance details

Defined in Data.Proxy

Methods

(==) :: Proxy s -> Proxy s -> Bool Source #

(/=) :: Proxy s -> Proxy s -> Bool Source #

Eq a => Eq (Arg a b)

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Methods

(==) :: Arg a b -> Arg a b -> Bool Source #

(/=) :: Arg a b -> Arg a b -> Bool Source #

Eq (TypeRep a)

Since: base-2.1

Instance details

Defined in Data.Typeable.Internal

Methods

(==) :: TypeRep a -> TypeRep a -> Bool Source #

(/=) :: TypeRep a -> TypeRep a -> Bool Source #

Eq (U1 p)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

(==) :: U1 p -> U1 p -> Bool Source #

(/=) :: U1 p -> U1 p -> Bool Source #

Eq (V1 p)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

(==) :: V1 p -> V1 p -> Bool Source #

(/=) :: V1 p -> V1 p -> Bool Source #

(Eq k, Eq a) => Eq (Map k a) 
Instance details

Defined in Data.Map.Internal

Methods

(==) :: Map k a -> Map k a -> Bool Source #

(/=) :: Map k a -> Map k a -> Bool Source #

(Eq a, Eq b) => Eq (a, b) 
Instance details

Defined in GHC.Classes

Methods

(==) :: (a, b) -> (a, b) -> Bool Source #

(/=) :: (a, b) -> (a, b) -> Bool Source #

Eq a => Eq (Const a b)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Const

Methods

(==) :: Const a b -> Const a b -> Bool Source #

(/=) :: Const a b -> Const a b -> Bool Source #

Eq (f a) => Eq (Ap f a)

Since: base-4.12.0.0

Instance details

Defined in Data.Monoid

Methods

(==) :: Ap f a -> Ap f a -> Bool Source #

(/=) :: Ap f a -> Ap f a -> Bool Source #

Eq (a :~: b)

Since: base-4.7.0.0

Instance details

Defined in Data.Type.Equality

Methods

(==) :: (a :~: b) -> (a :~: b) -> Bool Source #

(/=) :: (a :~: b) -> (a :~: b) -> Bool Source #

Eq (OrderingI a b) 
Instance details

Defined in Data.Type.Ord

Methods

(==) :: OrderingI a b -> OrderingI a b -> Bool Source #

(/=) :: OrderingI a b -> OrderingI a b -> Bool Source #

Eq (f p) => Eq (Rec1 f p)

Since: base-4.7.0.0

Instance details

Defined in GHC.Generics

Methods

(==) :: Rec1 f p -> Rec1 f p -> Bool Source #

(/=) :: Rec1 f p -> Rec1 f p -> Bool Source #

Eq (URec (Ptr ()) p)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

(==) :: URec (Ptr ()) p -> URec (Ptr ()) p -> Bool Source #

(/=) :: URec (Ptr ()) p -> URec (Ptr ()) p -> Bool Source #

Eq (URec Char p)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

(==) :: URec Char p -> URec Char p -> Bool Source #

(/=) :: URec Char p -> URec Char p -> Bool Source #

Eq (URec Double p)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

(==) :: URec Double p -> URec Double p -> Bool Source #

(/=) :: URec Double p -> URec Double p -> Bool Source #

Eq (URec Float p) 
Instance details

Defined in GHC.Generics

Methods

(==) :: URec Float p -> URec Float p -> Bool Source #

(/=) :: URec Float p -> URec Float p -> Bool Source #

Eq (URec Int p)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

(==) :: URec Int p -> URec Int p -> Bool Source #

(/=) :: URec Int p -> URec Int p -> Bool Source #

Eq (URec Word p)

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

(==) :: URec Word p -> URec Word p -> Bool Source #

(/=) :: URec Word p -> URec Word p -> Bool Source #

(Eq a, Eq b, Eq c) => Eq (a, b, c) 
Instance details

Defined in GHC.Classes

Methods

(==) :: (a, b, c) -> (a, b, c) -> Bool Source #

(/=) :: (a, b, c) -> (a, b, c) -> Bool Source #

(Eq1 f, Eq1 g, Eq a) => Eq (Product f g a)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Product

Methods

(==) :: Product f g a -> Product f g a -> Bool Source #

(/=) :: Product f g a -> Product f g a -> Bool Source #

(Eq1 f, Eq1 g, Eq a) => Eq (Sum f g a)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Sum

Methods

(==) :: Sum f g a -> Sum f g a -> Bool Source #

(/=) :: Sum f g a -> Sum f g a -> Bool Source #

Eq (a :~~: b)

Since: base-4.10.0.0

Instance details

Defined in Data.Type.Equality

Methods

(==) :: (a :~~: b) -> (a :~~: b) -> Bool Source #

(/=) :: (a :~~: b) -> (a :~~: b) -> Bool Source #

(Eq (f p), Eq (g p)) => Eq ((f :*: g) p)

Since: base-4.7.0.0

Instance details

Defined in GHC.Generics

Methods

(==) :: (f :*: g) p -> (f :*: g) p -> Bool Source #

(/=) :: (f :*: g) p -> (f :*: g) p -> Bool Source #

(Eq (f p), Eq (g p)) => Eq ((f :+: g) p)

Since: base-4.7.0.0

Instance details

Defined in GHC.Generics

Methods

(==) :: (f :+: g) p -> (f :+: g) p -> Bool Source #

(/=) :: (f :+: g) p -> (f :+: g) p -> Bool Source #

Eq c => Eq (K1 i c p)

Since: base-4.7.0.0

Instance details

Defined in GHC.Generics

Methods

(==) :: K1 i c p -> K1 i c p -> Bool Source #

(/=) :: K1 i c p -> K1 i c p -> Bool Source #

(Eq a, Eq b, Eq c, Eq d) => Eq (a, b, c, d) 
Instance details

Defined in GHC.Classes

Methods

(==) :: (a, b, c, d) -> (a, b, c, d) -> Bool Source #

(/=) :: (a, b, c, d) -> (a, b, c, d) -> Bool Source #