ghc-experimental-9.1300.0: Experimental features of GHC's standard library
Safe HaskellTrustworthy
LanguageHaskell2010

Prelude.Experimental

Synopsis

Documentation

data List a Source #

The builtin linked list type.

In Haskell, lists are one of the most important data types as they are often used analogous to loops in imperative programming languages. These lists are singly linked, which makes them unsuited for operations that require \(\mathcal{O}(1)\) access. Instead, they are intended to be traversed.

You can use List a or [a] in type signatures:

length :: [a] -> Int

or

length :: List a -> Int

They are fully equivalent, and List a will be normalised to [a].

Usage

Lists are constructed recursively using the right-associative constructor operator (or cons) (:) :: a -> [a] -> [a], which prepends an element to a list, and the empty list [].

(1 : 2 : 3 : []) == (1 : (2 : (3 : []))) == [1, 2, 3]

Lists can also be constructed using list literals of the form [x_1, x_2, ..., x_n] which are syntactic sugar and, unless -XOverloadedLists is enabled, are translated into uses of (:) and []

String literals, like "I 💜 hs", are translated into Lists of characters, ['I', ' ', '💜', ' ', 'h', 's'].

Implementation

Expand

Internally and in memory, all the above are represented like this, with arrows being pointers to locations in memory.

╭───┬───┬──╮   ╭───┬───┬──╮   ╭───┬───┬──╮   ╭────╮
│(:)│   │ ─┼──>│(:)│   │ ─┼──>│(:)│   │ ─┼──>│ [] │
╰───┴─┼─┴──╯   ╰───┴─┼─┴──╯   ╰───┴─┼─┴──╯   ╰────╯
      v              v              v
      1              2              3

Examples

Expand
>>> ['H', 'a', 's', 'k', 'e', 'l', 'l']
"Haskell"

>>> 1 : [4, 1, 5, 9]
[1,4,1,5,9]

>>> [] : [] : []
[[],[]]

Since: ghc-internal-0.10.0

Instances

Instances details
Eq1 [] Source #

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

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

Ord1 [] Source #

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

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

Read1 [] Source #

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

liftReadsPrec :: (Int -> ReadS a) -> ReadS [a] -> Int -> ReadS [a] Source #

liftReadList :: (Int -> ReadS a) -> ReadS [a] -> ReadS [[a]] Source #

liftReadPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec [a] Source #

liftReadListPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec [[a]] Source #

Show1 [] Source #

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

liftShowsPrec :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> Int -> [a] -> ShowS Source #

liftShowList :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> [[a]] -> ShowS Source #

Alternative [] Source #

Combines lists by concatenation, starting from the empty list.

Since: base-2.1

Instance details

Defined in GHC.Internal.Base

Methods

empty :: [a] Source #

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

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

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

Applicative [] Source #

Since: base-2.1

Instance details

Defined in GHC.Internal.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 #

Functor [] Source #

Since: base-2.1

Instance details

Defined in GHC.Internal.Base

Methods

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

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

Monad [] Source #

Since: base-2.1

Instance details

Defined in GHC.Internal.Base

Methods

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

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

return :: a -> [a] Source #

MonadPlus [] Source #

Combines lists by concatenation, starting from the empty list.

Since: base-2.1

Instance details

Defined in GHC.Internal.Base

Methods

mzero :: [a] Source #

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

MonadFail [] Source #

Since: base-4.9.0.0

Instance details

Defined in GHC.Internal.Control.Monad.Fail

Methods

fail :: String -> [a] Source #

MonadFix [] Source #

Since: base-2.1

Instance details

Defined in GHC.Internal.Control.Monad.Fix

Methods

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

MonadZip [] Source #

Since: ghc-internal-4.3.1.0

Instance details

Defined in GHC.Internal.Control.Monad.Zip

Methods

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

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

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

Foldable [] Source #

Since: base-2.1

Instance details

Defined in GHC.Internal.Data.Foldable

Methods

fold :: Monoid m => [m] -> m Source #

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

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

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

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

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

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

foldr1 :: (a -> a -> a) -> [a] -> a Source #

foldl1 :: (a -> a -> a) -> [a] -> a Source #

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

null :: [a] -> Bool Source #

length :: [a] -> Int Source #

elem :: Eq a => a -> [a] -> Bool Source #

maximum :: Ord a => [a] -> a Source #

minimum :: Ord a => [a] -> a Source #

sum :: Num a => [a] -> a Source #

product :: Num a => [a] -> a Source #

Traversable [] Source #

Since: base-2.1

Instance details

Defined in GHC.Internal.Data.Traversable

Methods

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

sequenceA :: Applicative f => [f a] -> f [a] Source #

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

sequence :: Monad m => [m a] -> m [a] Source #

Generic1 [] Source # 
Instance details

Defined in GHC.Internal.Generics

Associated Types

type Rep1 []

Since: base-4.6.0.0

Instance details

Defined in GHC.Internal.Generics

type Rep1 [] = D1 ('MetaData "List" "GHC.Internal.Types" "ghc-internal" 'False) (C1 ('MetaCons "[]" 'PrefixI 'False) (U1 :: Type -> Type) :+: C1 ('MetaCons ":" ('InfixI 'RightAssociative 5) 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) Par1 :*: S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec1 [])))

Methods

from1 :: [a] -> Rep1 [] a Source #

to1 :: Rep1 [] a -> [a] Source #

Lift a => Lift ([a] :: Type) Source # 
Instance details

Defined in GHC.Internal.TH.Lift

Methods

lift :: Quote m => [a] -> m Exp Source #

liftTyped :: forall (m :: Type -> Type). Quote m => [a] -> Code m [a] Source #

IsChar c => PrintfArg [c] Source #

Since: base-2.1

Instance details

Defined in Text.Printf

Methods

formatArg :: [c] -> FieldFormatter Source #

parseFormat :: [c] -> ModifierParser Source #

IsChar c => PrintfType [c] Source #

Since: base-2.1

Instance details

Defined in Text.Printf

Methods

spr :: String -> [UPrintf] -> [c]

Monoid [a] Source #

Since: base-2.1

Instance details

Defined in GHC.Internal.Base

Methods

mempty :: [a] Source #

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

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

Semigroup [a] Source #

Since: base-4.9.0.0

Instance details

Defined in GHC.Internal.Base

Methods

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

sconcat :: NonEmpty [a] -> [a] Source #

stimes :: Integral b => b -> [a] -> [a] Source #

Eq a => Eq [a] Source # 
Instance details

Defined in GHC.Internal.Classes

Methods

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

(/=) :: [a] -> [a] -> Bool Source #

Ord a => Ord [a] Source # 
Instance details

Defined in GHC.Internal.Classes

Methods

compare :: [a] -> [a] -> Ordering Source #

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

(<=) :: [a] -> [a] -> Bool Source #

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

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

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

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

Data a => Data [a] Source #

For historical reasons, the constructor name used for (:) is "(:)". In a derived instance, it would be ":".

Since: base-4.0.0.0

Instance details

Defined in GHC.Internal.Data.Data

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> [a] -> c [a] Source #

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c [a] Source #

toConstr :: [a] -> Constr Source #

dataTypeOf :: [a] -> DataType Source #

dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c [a]) Source #

dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c [a]) Source #

gmapT :: (forall b. Data b => b -> b) -> [a] -> [a] Source #

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> [a] -> r Source #

gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> [a] -> r Source #

gmapQ :: (forall d. Data d => d -> u) -> [a] -> [u] Source #

gmapQi :: Int -> (forall d. Data d => d -> u) -> [a] -> u Source #

gmapM :: Monad m => (forall d. Data d => d -> m d) -> [a] -> m [a] Source #

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> [a] -> m [a] Source #

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> [a] -> m [a] Source #

a ~ Char => IsString [a] Source #

(a ~ Char) context was introduced in 4.9.0.0

Since: base-2.1

Instance details

Defined in GHC.Internal.Data.String

Methods

fromString :: String -> [a] Source #

Generic [a] Source # 
Instance details

Defined in GHC.Internal.Generics

Associated Types

type Rep [a]

Since: base-4.6.0.0

Instance details

Defined in GHC.Internal.Generics

type Rep [a] = D1 ('MetaData "List" "GHC.Internal.Types" "ghc-internal" 'False) (C1 ('MetaCons "[]" 'PrefixI 'False) (U1 :: Type -> Type) :+: C1 ('MetaCons ":" ('InfixI 'RightAssociative 5) 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 a) :*: S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 [a])))

Methods

from :: [a] -> Rep [a] x Source #

to :: Rep [a] x -> [a] Source #

IsList [a] Source #

Since: base-4.7.0.0

Instance details

Defined in GHC.Internal.IsList

Associated Types

type Item [a] 
Instance details

Defined in GHC.Internal.IsList

type Item [a] = a

Methods

fromList :: [Item [a]] -> [a] Source #

fromListN :: Int -> [Item [a]] -> [a] Source #

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

Read a => Read [a] Source #

Since: base-2.1

Instance details

Defined in GHC.Internal.Read

Methods

readsPrec :: Int -> ReadS [a] Source #

readList :: ReadS [[a]] Source #

readPrec :: ReadPrec [a] Source #

readListPrec :: ReadPrec [[a]] Source #

Show a => Show [a] Source #

Since: base-2.1

Instance details

Defined in GHC.Internal.Show

Methods

showsPrec :: Int -> [a] -> ShowS Source #

show :: [a] -> String Source #

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

type Rep1 [] Source #

Since: base-4.6.0.0

Instance details

Defined in GHC.Internal.Generics

type Rep1 [] = D1 ('MetaData "List" "GHC.Internal.Types" "ghc-internal" 'False) (C1 ('MetaCons "[]" 'PrefixI 'False) (U1 :: Type -> Type) :+: C1 ('MetaCons ":" ('InfixI 'RightAssociative 5) 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) Par1 :*: S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec1 [])))
type Rep [a] Source #

Since: base-4.6.0.0

Instance details

Defined in GHC.Internal.Generics

type Rep [a] = D1 ('MetaData "List" "GHC.Internal.Types" "ghc-internal" 'False) (C1 ('MetaCons "[]" 'PrefixI 'False) (U1 :: Type -> Type) :+: C1 ('MetaCons ":" ('InfixI 'RightAssociative 5) 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 a) :*: S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 [a])))
type Item [a] Source # 
Instance details

Defined in GHC.Internal.IsList

type Item [a] = a

Tuple/sum syntax families and tycons

module Data.Tuple.Experimental

module Data.Sum.Experimental