Safe Haskell | Safe-Inferred |
---|---|
Language | Haskell98 |
NumericPrelude.Base
Description
The only point of this module is to reexport items that we want from the standard Prelude.
Synopsis
- (!!) :: [a] -> Int -> a
- ($) :: forall (r :: RuntimeRep) a (b :: TYPE r). (a -> b) -> a -> b
- ($!) :: forall (r :: RuntimeRep) a (b :: TYPE r). (a -> b) -> a -> b
- (&&) :: Bool -> Bool -> Bool
- (++) :: [a] -> [a] -> [a]
- (.) :: (b -> c) -> (a -> b) -> a -> c
- (=<<) :: Monad m => (a -> m b) -> m a -> m b
- data Bool
- class Bounded a where
- data Char
- data Either a b
- class Enum a where
- succ :: a -> a
- pred :: a -> a
- toEnum :: Int -> a
- fromEnum :: a -> Int
- enumFrom :: a -> [a]
- enumFromThen :: a -> a -> [a]
- enumFromTo :: a -> a -> [a]
- enumFromThenTo :: a -> a -> a -> [a]
- class Eq a where
- type FilePath = String
- class Functor (f :: Type -> Type) where
- data IO a
- type IOError = IOException
- data Maybe a
- class Applicative m => Monad (m :: Type -> Type) where
- fail :: MonadFail m => String -> m a
- class Eq a => Ord a where
- data Ordering
- class Read a where
- type ReadS a = String -> [(a, String)]
- class Show a where
- type ShowS = String -> String
- type String = [Char]
- all :: Foldable t => (a -> Bool) -> t a -> Bool
- and :: Foldable t => t Bool -> Bool
- any :: Foldable t => (a -> Bool) -> t a -> Bool
- appendFile :: FilePath -> String -> IO ()
- asTypeOf :: a -> a -> a
- break :: (a -> Bool) -> [a] -> ([a], [a])
- concat :: Foldable t => t [a] -> [a]
- concatMap :: Foldable t => (a -> [b]) -> t a -> [b]
- const :: a -> b -> a
- curry :: ((a, b) -> c) -> a -> b -> c
- cycle :: [a] -> [a]
- drop :: Int -> [a] -> [a]
- dropWhile :: (a -> Bool) -> [a] -> [a]
- either :: (a -> c) -> (b -> c) -> Either a b -> c
- elem :: (Foldable t, Eq a) => a -> t a -> Bool
- error :: forall (r :: RuntimeRep) (a :: TYPE r). HasCallStack => [Char] -> a
- filter :: (a -> Bool) -> [a] -> [a]
- flip :: (a -> b -> c) -> b -> a -> c
- foldl :: Foldable t => (b -> a -> b) -> b -> t a -> b
- foldl1 :: Foldable t => (a -> a -> a) -> t a -> a
- foldr :: Foldable t => (a -> b -> b) -> b -> t a -> b
- foldr1 :: Foldable t => (a -> a -> a) -> t a -> a
- fst :: (a, b) -> a
- getChar :: IO Char
- getContents :: IO String
- getLine :: IO String
- head :: [a] -> a
- id :: a -> a
- init :: [a] -> [a]
- interact :: (String -> String) -> IO ()
- ioError :: IOError -> IO a
- iterate :: (a -> a) -> a -> [a]
- last :: [a] -> a
- length :: Foldable t => t a -> Int
- lex :: ReadS String
- lines :: String -> [String]
- lookup :: Eq a => a -> [(a, b)] -> Maybe b
- map :: (a -> b) -> [a] -> [b]
- mapM :: (Traversable t, Monad m) => (a -> m b) -> t a -> m (t b)
- mapM_ :: (Foldable t, Monad m) => (a -> m b) -> t a -> m ()
- maximum :: (Foldable t, Ord a) => t a -> a
- maybe :: b -> (a -> b) -> Maybe a -> b
- minimum :: (Foldable t, Ord a) => t a -> a
- not :: Bool -> Bool
- notElem :: (Foldable t, Eq a) => a -> t a -> Bool
- null :: Foldable t => t a -> Bool
- or :: Foldable t => t Bool -> Bool
- otherwise :: Bool
- print :: Show a => a -> IO ()
- putChar :: Char -> IO ()
- putStr :: String -> IO ()
- putStrLn :: String -> IO ()
- read :: Read a => String -> a
- readFile :: FilePath -> IO String
- readIO :: Read a => String -> IO a
- readLn :: Read a => IO a
- readParen :: Bool -> ReadS a -> ReadS a
- reads :: Read a => ReadS a
- realToFrac :: (Real a, Fractional b) => a -> b
- repeat :: a -> [a]
- replicate :: Int -> a -> [a]
- reverse :: [a] -> [a]
- scanl :: (b -> a -> b) -> b -> [a] -> [b]
- scanl1 :: (a -> a -> a) -> [a] -> [a]
- scanr :: (a -> b -> b) -> b -> [a] -> [b]
- scanr1 :: (a -> a -> a) -> [a] -> [a]
- seq :: forall (r :: RuntimeRep) a (b :: TYPE r). a -> b -> b
- sequence :: (Traversable t, Monad m) => t (m a) -> m (t a)
- sequence_ :: (Foldable t, Monad m) => t (m a) -> m ()
- showChar :: Char -> ShowS
- showParen :: Bool -> ShowS -> ShowS
- showString :: String -> ShowS
- shows :: Show a => a -> ShowS
- snd :: (a, b) -> b
- span :: (a -> Bool) -> [a] -> ([a], [a])
- splitAt :: Int -> [a] -> ([a], [a])
- tail :: [a] -> [a]
- take :: Int -> [a] -> [a]
- takeWhile :: (a -> Bool) -> [a] -> [a]
- uncurry :: (a -> b -> c) -> (a, b) -> c
- undefined :: forall (r :: RuntimeRep) (a :: TYPE r). HasCallStack => a
- unlines :: [String] -> String
- until :: (a -> Bool) -> (a -> a) -> a -> a
- unwords :: [String] -> String
- unzip :: [(a, b)] -> ([a], [b])
- unzip3 :: [(a, b, c)] -> ([a], [b], [c])
- userError :: String -> IOError
- words :: String -> [String]
- writeFile :: FilePath -> String -> IO ()
- zip :: [a] -> [b] -> [(a, b)]
- zip3 :: [a] -> [b] -> [c] -> [(a, b, c)]
- zipWith :: (a -> b -> c) -> [a] -> [b] -> [c]
- zipWith3 :: (a -> b -> c -> d) -> [a] -> [b] -> [c] -> [d]
- (||) :: Bool -> Bool -> Bool
- catch :: IO a -> (IOError -> IO a) -> IO a
- ifThenElse :: Bool -> a -> a -> a
Documentation
(!!) :: [a] -> Int -> a infixl 9 #
List index (subscript) operator, starting from 0.
It is an instance of the more general genericIndex
,
which takes an index of any integral type.
($) :: forall (r :: RuntimeRep) a (b :: TYPE r). (a -> b) -> a -> b infixr 0 #
Application operator. This operator is redundant, since ordinary
application (f x)
means the same as (f
. However, $
x)$
has
low, right-associative binding precedence, so it sometimes allows
parentheses to be omitted; for example:
f $ g $ h x = f (g (h x))
It is also useful in higher-order situations, such as
,
or map
($
0) xs
.zipWith
($
) fs xs
Note that (
is levity-polymorphic in its result type, so that
$
)foo
where $
Truefoo :: Bool -> Int#
is well-typed.
($!) :: forall (r :: RuntimeRep) a (b :: TYPE r). (a -> b) -> a -> b infixr 0 #
Strict (call-by-value) application operator. It takes a function and an argument, evaluates the argument to weak head normal form (WHNF), then calls the function with that value.
(++) :: [a] -> [a] -> [a] infixr 5 #
Append two lists, i.e.,
[x1, ..., xm] ++ [y1, ..., yn] == [x1, ..., xm, y1, ..., yn] [x1, ..., xm] ++ [y1, ...] == [x1, ..., xm, y1, ...]
If the first list is not finite, the result is the first list.
(=<<) :: Monad m => (a -> m b) -> m a -> m b infixr 1 #
Same as >>=
, but with the arguments interchanged.
Instances
Bounded Bool | Since: base-2.1 |
Enum Bool | Since: base-2.1 |
Eq Bool | |
Ord Bool | |
Read Bool | Since: base-2.1 |
Show Bool | Since: base-2.1 |
Ix Bool | Since: base-2.1 |
Generic Bool | Since: base-4.6.0.0 |
Testable Bool | |
Arbitrary Bool | |
CoArbitrary Bool | |
Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Bool -> Gen b -> Gen b # | |
Storable Bool | Since: base-2.1 |
Defined in Foreign.Storable | |
NFData Bool | |
Defined in Control.DeepSeq | |
Random Bool | |
Uniform Bool | |
Defined in System.Random.Internal Methods uniformM :: StatefulGen g m => g -> m Bool # | |
UniformRange Bool | |
Defined in System.Random.Internal | |
SingKind Bool | Since: base-4.9.0.0 |
Defined in GHC.Generics Associated Types type DemoteRep Bool | |
C Bool Source # | |
Lift Bool | |
SingI 'False | Since: base-4.9.0.0 |
Defined in GHC.Generics | |
SingI 'True | Since: base-4.9.0.0 |
Defined in GHC.Generics | |
type Rep Bool | |
type DemoteRep Bool | |
Defined in GHC.Generics | |
data Sing (a :: Bool) | |
The Bounded
class is used to name the upper and lower limits of a
type. Ord
is not a superclass of Bounded
since types that are not
totally ordered may also have upper and lower bounds.
The Bounded
class may be derived for any enumeration type;
minBound
is the first constructor listed in the data
declaration
and maxBound
is the last.
Bounded
may also be derived for single-constructor datatypes whose
constituent types are in Bounded
.
Instances
Bounded Bool | Since: base-2.1 |
Bounded Char | Since: base-2.1 |
Bounded Int | Since: base-2.1 |
Bounded Int8 | Since: base-2.1 |
Bounded Int16 | Since: base-2.1 |
Bounded Int32 | Since: base-2.1 |
Bounded Int64 | Since: base-2.1 |
Bounded Ordering | Since: base-2.1 |
Bounded Word | Since: base-2.1 |
Bounded Word8 | Since: base-2.1 |
Bounded Word16 | Since: base-2.1 |
Bounded Word32 | Since: base-2.1 |
Bounded Word64 | Since: base-2.1 |
Bounded VecCount | Since: base-4.10.0.0 |
Bounded VecElem | Since: base-4.10.0.0 |
Bounded () | Since: base-2.1 |
Bounded All | Since: base-2.1 |
Bounded Any | Since: base-2.1 |
Bounded Associativity | Since: base-4.9.0.0 |
Defined in GHC.Generics | |
Bounded SourceUnpackedness | Since: base-4.9.0.0 |
Defined in GHC.Generics | |
Bounded SourceStrictness | Since: base-4.9.0.0 |
Defined in GHC.Generics | |
Bounded DecidedStrictness | Since: base-4.9.0.0 |
Defined in GHC.Generics | |
Bounded CChar | |
Bounded CSChar | |
Bounded CUChar | |
Bounded CShort | |
Bounded CUShort | |
Bounded CInt | |
Bounded CUInt | |
Bounded CLong | |
Bounded CULong | |
Bounded CLLong | |
Bounded CULLong | |
Bounded CBool | |
Bounded CPtrdiff | |
Bounded CSize | |
Bounded CWchar | |
Bounded CSigAtomic | |
Defined in Foreign.C.Types | |
Bounded CIntPtr | |
Bounded CUIntPtr | |
Bounded CIntMax | |
Bounded CUIntMax | |
Bounded GeneralCategory | Since: base-2.1 |
Defined in GHC.Unicode | |
Bounded Extension | |
Bounded T Source # | |
Bounded a => Bounded (Min a) | Since: base-4.9.0.0 |
Bounded a => Bounded (Max a) | Since: base-4.9.0.0 |
Bounded a => Bounded (First a) | Since: base-4.9.0.0 |
Bounded a => Bounded (Last a) | Since: base-4.9.0.0 |
Bounded m => Bounded (WrappedMonoid m) | Since: base-4.9.0.0 |
Defined in Data.Semigroup | |
Bounded a => Bounded (Identity a) | Since: base-4.9.0.0 |
Bounded a => Bounded (Dual a) | Since: base-2.1 |
Bounded a => Bounded (Sum a) | Since: base-2.1 |
Bounded a => Bounded (Product a) | Since: base-2.1 |
Bounded a => Bounded (Down a) | Since: base-4.14.0.0 |
(Ord a, Num a, Bounded a) => Bounded (T a) | |
Bounded a => Bounded (T a) Source # | |
Bounded a => Bounded (T a) Source # | |
(Bounded a, Bounded b) => Bounded (a, b) | Since: base-2.1 |
Bounded (Proxy t) | Since: base-4.7.0.0 |
(Bounded a, Bounded b, Bounded c) => Bounded (a, b, c) | Since: base-2.1 |
Bounded a => Bounded (Const a b) | Since: base-4.9.0.0 |
(Applicative f, Bounded a) => Bounded (Ap f a) | Since: base-4.12.0.0 |
a ~ b => Bounded (a :~: b) | Since: base-4.7.0.0 |
(Bounded a, Bounded b, Bounded c, Bounded d) => Bounded (a, b, c, d) | Since: base-2.1 |
a ~~ b => Bounded (a :~~: b) | Since: base-4.10.0.0 |
(Bounded a, Bounded b, Bounded c, Bounded d, Bounded e) => Bounded (a, b, c, d, e) | Since: base-2.1 |
(Bounded a, Bounded b, Bounded c, Bounded d, Bounded e, Bounded f) => Bounded (a, b, c, d, e, f) | Since: base-2.1 |
(Bounded a, Bounded b, Bounded c, Bounded d, Bounded e, Bounded f, Bounded g) => Bounded (a, b, c, d, e, f, g) | Since: base-2.1 |
(Bounded a, Bounded b, Bounded c, Bounded d, Bounded e, Bounded f, Bounded g, Bounded h) => Bounded (a, b, c, d, e, f, g, h) | Since: base-2.1 |
(Bounded a, Bounded b, Bounded c, Bounded d, Bounded e, Bounded f, Bounded g, Bounded h, Bounded i) => Bounded (a, b, c, d, e, f, g, h, i) | Since: base-2.1 |
(Bounded a, Bounded b, Bounded c, Bounded d, Bounded e, Bounded f, Bounded g, Bounded h, Bounded i, Bounded j) => Bounded (a, b, c, d, e, f, g, h, i, j) | Since: base-2.1 |
(Bounded a, Bounded b, Bounded c, Bounded d, Bounded e, Bounded f, Bounded g, Bounded h, Bounded i, Bounded j, Bounded k) => Bounded (a, b, c, d, e, f, g, h, i, j, k) | Since: base-2.1 |
(Bounded a, Bounded b, Bounded c, Bounded d, Bounded e, Bounded f, Bounded g, Bounded h, Bounded i, Bounded j, Bounded k, Bounded l) => Bounded (a, b, c, d, e, f, g, h, i, j, k, l) | Since: base-2.1 |
(Bounded a, Bounded b, Bounded c, Bounded d, Bounded e, Bounded f, Bounded g, Bounded h, Bounded i, Bounded j, Bounded k, Bounded l, Bounded m) => Bounded (a, b, c, d, e, f, g, h, i, j, k, l, m) | Since: base-2.1 |
(Bounded a, Bounded b, Bounded c, Bounded d, Bounded e, Bounded f, Bounded g, Bounded h, Bounded i, Bounded j, Bounded k, Bounded l, Bounded m, Bounded n) => Bounded (a, b, c, d, e, f, g, h, i, j, k, l, m, n) | Since: base-2.1 |
(Bounded a, Bounded b, Bounded c, Bounded d, Bounded e, Bounded f, Bounded g, Bounded h, Bounded i, Bounded j, Bounded k, Bounded l, Bounded m, Bounded n, Bounded o) => Bounded (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) | Since: base-2.1 |
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
Bounded Char | Since: base-2.1 |
Enum Char | Since: base-2.1 |
Eq Char | |
Ord Char | |
Read Char | Since: base-2.1 |
Show Char | Since: base-2.1 |
Ix Char | Since: base-2.1 |
Arbitrary Char | |
CoArbitrary Char | |
Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Char -> Gen b -> Gen b # | |
Storable Char | Since: base-2.1 |
Defined in Foreign.Storable | |
NFData Char | |
Defined in Control.DeepSeq | |
Random Char | |
Uniform Char | |
Defined in System.Random.Internal Methods uniformM :: StatefulGen g m => g -> m Char # | |
UniformRange Char | |
Defined in System.Random.Internal | |
ErrorList Char | |
Defined in Control.Monad.Trans.Error | |
Lift Char | |
Monad m => Stream ByteString m Char | |
Defined in Text.Parsec.Prim Methods uncons :: ByteString -> m (Maybe (Char, ByteString)) # | |
Monad m => Stream ByteString m Char | |
Defined in Text.Parsec.Prim Methods uncons :: ByteString -> m (Maybe (Char, ByteString)) # | |
Monad m => Stream Text m Char | |
Monad m => Stream Text m Char | |
Generic1 (URec Char :: k -> Type) | Since: base-4.9.0.0 |
Foldable (UChar :: Type -> Type) | Since: base-4.9.0.0 |
Defined in Data.Foldable Methods fold :: Monoid m => UChar m -> m # foldMap :: Monoid m => (a -> m) -> UChar a -> m # foldMap' :: Monoid m => (a -> m) -> UChar a -> m # foldr :: (a -> b -> b) -> b -> UChar a -> b # foldr' :: (a -> b -> b) -> b -> UChar a -> b # foldl :: (b -> a -> b) -> b -> UChar a -> b # foldl' :: (b -> a -> b) -> b -> UChar a -> b # foldr1 :: (a -> a -> a) -> UChar a -> a # foldl1 :: (a -> a -> a) -> UChar a -> a # elem :: Eq a => a -> UChar a -> Bool # maximum :: Ord a => UChar a -> a # minimum :: Ord a => UChar a -> a # | |
Traversable (UChar :: Type -> Type) | Since: base-4.9.0.0 |
Functor (URec Char :: Type -> Type) | Since: base-4.9.0.0 |
Eq (URec Char p) | Since: base-4.9.0.0 |
Ord (URec Char p) | Since: base-4.9.0.0 |
Defined in GHC.Generics | |
Show (URec Char p) | Since: base-4.9.0.0 |
Generic (URec Char p) | Since: base-4.9.0.0 |
data URec Char (p :: k) | Used for marking occurrences of Since: base-4.9.0.0 |
type Rep1 (URec Char :: k -> Type) | |
Defined in GHC.Generics | |
type Rep (URec Char p) | |
Defined in GHC.Generics |
The Either
type represents values with two possibilities: a value of
type
is either Either
a b
or Left
a
.Right
b
The Either
type is sometimes used to represent a value which is
either correct or an error; by convention, the Left
constructor is
used to hold an error value and the Right
constructor is used to
hold a correct value (mnemonic: "right" also means "correct").
Examples
The type
is the type of values which can be either
a Either
String
Int
String
or an Int
. The Left
constructor can be used only on
String
s, and the Right
constructor can be used only on Int
s:
>>>
let s = Left "foo" :: Either String Int
>>>
s
Left "foo">>>
let n = Right 3 :: Either String Int
>>>
n
Right 3>>>
:type s
s :: Either String Int>>>
:type n
n :: Either String Int
The fmap
from our Functor
instance will ignore Left
values, but
will apply the supplied function to values contained in a Right
:
>>>
let s = Left "foo" :: Either String Int
>>>
let n = Right 3 :: Either String Int
>>>
fmap (*2) s
Left "foo">>>
fmap (*2) n
Right 6
The Monad
instance for Either
allows us to chain together multiple
actions which may fail, and fail overall if any of the individual
steps failed. First we'll write a function that can either parse an
Int
from a Char
, or fail.
>>>
import Data.Char ( digitToInt, isDigit )
>>>
:{
let parseEither :: Char -> Either String Int parseEither c | isDigit c = Right (digitToInt c) | otherwise = Left "parse error">>>
:}
The following should work, since both '1'
and '2'
can be
parsed as Int
s.
>>>
:{
let parseMultiple :: Either String Int parseMultiple = do x <- parseEither '1' y <- parseEither '2' return (x + y)>>>
:}
>>>
parseMultiple
Right 3
But the following should fail overall, since the first operation where
we attempt to parse 'm'
as an Int
will fail:
>>>
:{
let parseMultiple :: Either String Int parseMultiple = do x <- parseEither 'm' y <- parseEither '2' return (x + y)>>>
:}
>>>
parseMultiple
Left "parse error"
Instances
Arbitrary2 Either | |
Defined in Test.QuickCheck.Arbitrary Methods liftArbitrary2 :: Gen a -> Gen b -> Gen (Either a b) # liftShrink2 :: (a -> [a]) -> (b -> [b]) -> Either a b -> [Either a b] # | |
Eq2 Either | Since: base-4.9.0.0 |
Ord2 Either | Since: base-4.9.0.0 |
Defined in Data.Functor.Classes | |
Read2 Either | Since: base-4.9.0.0 |
Defined in Data.Functor.Classes Methods liftReadsPrec2 :: (Int -> ReadS a) -> ReadS [a] -> (Int -> ReadS b) -> ReadS [b] -> Int -> ReadS (Either a b) # liftReadList2 :: (Int -> ReadS a) -> ReadS [a] -> (Int -> ReadS b) -> ReadS [b] -> ReadS [Either a b] # liftReadPrec2 :: ReadPrec a -> ReadPrec [a] -> ReadPrec b -> ReadPrec [b] -> ReadPrec (Either a b) # liftReadListPrec2 :: ReadPrec a -> ReadPrec [a] -> ReadPrec b -> ReadPrec [b] -> ReadPrec [Either a b] # | |
Show2 Either | Since: base-4.9.0.0 |
NFData2 Either | Since: deepseq-1.4.3.0 |
Defined in Control.DeepSeq | |
(Lift a, Lift b) => Lift (Either a b :: Type) | |
Monad (Either e) | Since: base-4.4.0.0 |
Functor (Either a) | Since: base-3.0 |
Applicative (Either e) | Since: base-3.0 |
Foldable (Either a) | Since: base-4.7.0.0 |
Defined in Data.Foldable Methods fold :: Monoid m => Either a m -> m # foldMap :: Monoid m => (a0 -> m) -> Either a a0 -> m # foldMap' :: Monoid m => (a0 -> m) -> Either a a0 -> m # foldr :: (a0 -> b -> b) -> b -> Either a a0 -> b # foldr' :: (a0 -> b -> b) -> b -> Either a a0 -> b # foldl :: (b -> a0 -> b) -> b -> Either a a0 -> b # foldl' :: (b -> a0 -> b) -> b -> Either a a0 -> b # foldr1 :: (a0 -> a0 -> a0) -> Either a a0 -> a0 # foldl1 :: (a0 -> a0 -> a0) -> Either a a0 -> a0 # toList :: Either a a0 -> [a0] # length :: Either a a0 -> Int # elem :: Eq a0 => a0 -> Either a a0 -> Bool # maximum :: Ord a0 => Either a a0 -> a0 # minimum :: Ord a0 => Either a a0 -> a0 # | |
Traversable (Either a) | Since: base-4.7.0.0 |
Defined in Data.Traversable | |
Arbitrary a => Arbitrary1 (Either a) | |
Defined in Test.QuickCheck.Arbitrary Methods liftArbitrary :: Gen a0 -> Gen (Either a a0) # liftShrink :: (a0 -> [a0]) -> Either a a0 -> [Either a a0] # | |
Eq a => Eq1 (Either a) | Since: base-4.9.0.0 |
Ord a => Ord1 (Either a) | Since: base-4.9.0.0 |
Defined in Data.Functor.Classes | |
Read a => Read1 (Either a) | Since: base-4.9.0.0 |
Defined in Data.Functor.Classes Methods liftReadsPrec :: (Int -> ReadS a0) -> ReadS [a0] -> Int -> ReadS (Either a a0) # liftReadList :: (Int -> ReadS a0) -> ReadS [a0] -> ReadS [Either a a0] # liftReadPrec :: ReadPrec a0 -> ReadPrec [a0] -> ReadPrec (Either a a0) # liftReadListPrec :: ReadPrec a0 -> ReadPrec [a0] -> ReadPrec [Either a a0] # | |
Show a => Show1 (Either a) | Since: base-4.9.0.0 |
NFData a => NFData1 (Either a) | Since: deepseq-1.4.3.0 |
Defined in Control.DeepSeq | |
Generic1 (Either a :: Type -> Type) | Since: base-4.6.0.0 |
(Eq a, Eq b) => Eq (Either a b) | Since: base-2.1 |
(Ord a, Ord b) => Ord (Either a b) | Since: base-2.1 |
(Read a, Read b) => Read (Either a b) | Since: base-3.0 |
(Show a, Show b) => Show (Either a b) | Since: base-3.0 |
Generic (Either a b) | Since: base-4.6.0.0 |
Semigroup (Either a b) | Since: base-4.9.0.0 |
(Arbitrary a, Arbitrary b) => Arbitrary (Either a b) | |
(CoArbitrary a, CoArbitrary b) => CoArbitrary (Either a b) | |
Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Either a b -> Gen b0 -> Gen b0 # | |
(NFData a, NFData b) => NFData (Either a b) | |
Defined in Control.DeepSeq | |
type Rep1 (Either a :: Type -> Type) | |
Defined in GHC.Generics type Rep1 (Either a :: Type -> Type) = D1 ('MetaData "Either" "Data.Either" "base" 'False) (C1 ('MetaCons "Left" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 a)) :+: C1 ('MetaCons "Right" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) Par1)) | |
type Rep (Either a b) | |
Defined in GHC.Generics type Rep (Either a b) = D1 ('MetaData "Either" "Data.Either" "base" 'False) (C1 ('MetaCons "Left" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 a)) :+: C1 ('MetaCons "Right" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 b))) |
Class Enum
defines operations on sequentially ordered types.
The enumFrom
... methods are used in Haskell's translation of
arithmetic sequences.
Instances of Enum
may be derived for any enumeration type (types
whose constructors have no fields). The nullary constructors are
assumed to be numbered left-to-right by fromEnum
from 0
through n-1
.
See Chapter 10 of the Haskell Report for more details.
For any type that is an instance of class Bounded
as well as Enum
,
the following should hold:
- The calls
andsucc
maxBound
should result in a runtime error.pred
minBound
fromEnum
andtoEnum
should give a runtime error if the result value is not representable in the result type. For example,
is an error.toEnum
7 ::Bool
enumFrom
andenumFromThen
should be defined with an implicit bound, thus:
enumFrom x = enumFromTo x maxBound enumFromThen x y = enumFromThenTo x y bound where bound | fromEnum y >= fromEnum x = maxBound | otherwise = minBound
Methods
the successor of a value. For numeric types, succ
adds 1.
the predecessor of a value. For numeric types, pred
subtracts 1.
Convert from an Int
.
Convert to an Int
.
It is implementation-dependent what fromEnum
returns when
applied to a value that is too large to fit in an Int
.
Used in Haskell's translation of [n..]
with [n..] = enumFrom n
,
a possible implementation being enumFrom n = n : enumFrom (succ n)
.
For example:
enumFrom 4 :: [Integer] = [4,5,6,7,...]
enumFrom 6 :: [Int] = [6,7,8,9,...,maxBound :: Int]
enumFromThen :: a -> a -> [a] #
Used in Haskell's translation of [n,n'..]
with [n,n'..] = enumFromThen n n'
, a possible implementation being
enumFromThen n n' = n : n' : worker (f x) (f x n')
,
worker s v = v : worker s (s v)
, x = fromEnum n' - fromEnum n
and
f n y
| n > 0 = f (n - 1) (succ y)
| n < 0 = f (n + 1) (pred y)
| otherwise = y
For example:
enumFromThen 4 6 :: [Integer] = [4,6,8,10...]
enumFromThen 6 2 :: [Int] = [6,2,-2,-6,...,minBound :: Int]
enumFromTo :: a -> a -> [a] #
Used in Haskell's translation of [n..m]
with
[n..m] = enumFromTo n m
, a possible implementation being
enumFromTo n m
| n <= m = n : enumFromTo (succ n) m
| otherwise = []
.
For example:
enumFromTo 6 10 :: [Int] = [6,7,8,9,10]
enumFromTo 42 1 :: [Integer] = []
enumFromThenTo :: a -> a -> a -> [a] #
Used in Haskell's translation of [n,n'..m]
with
[n,n'..m] = enumFromThenTo n n' m
, a possible implementation
being enumFromThenTo n n' m = worker (f x) (c x) n m
,
x = fromEnum n' - fromEnum n
, c x = bool (>=) ((x 0)
f n y
| n > 0 = f (n - 1) (succ y)
| n < 0 = f (n + 1) (pred y)
| otherwise = y
and
worker s c v m
| c v m = v : worker s c (s v) m
| otherwise = []
For example:
enumFromThenTo 4 2 -6 :: [Integer] = [4,2,0,-2,-4,-6]
enumFromThenTo 6 8 2 :: [Int] = []
Instances
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, ==
is customarily
expected to implement an equivalence relationship where two values comparing
equal are indistinguishable by "public" functions, with a "public" function
being one not allowing to see implementation details. For example, for a
type representing non-normalised natural numbers modulo 100, a "public"
function doesn't make the difference between 1 and 201. It is expected to
have the following properties:
Instances
Eq Bool | |
Eq Char | |
Eq Double | Note that due to the presence of
Also note that
|
Eq Float | Note that due to the presence of
Also note that
|
Eq Int | |
Eq Int8 | Since: base-2.1 |
Eq Int16 | Since: base-2.1 |
Eq Int32 | Since: base-2.1 |
Eq Int64 | Since: base-2.1 |
Eq Integer | |
Eq Natural | Since: base-4.8.0.0 |
Eq Ordering | |
Eq Word | |
Eq Word8 | Since: base-2.1 |
Eq Word16 | Since: base-2.1 |
Eq Word32 | Since: base-2.1 |
Eq Word64 | Since: base-2.1 |
Eq SomeTypeRep | |
Defined in Data.Typeable.Internal | |
Eq Exp | |
Eq Match | |
Eq Clause | |
Eq Pat | |
Eq Type | |
Eq Dec | |
Eq Name | |
Eq FunDep | |
Eq InjectivityAnn | |
Defined in Language.Haskell.TH.Syntax Methods (==) :: InjectivityAnn -> InjectivityAnn -> Bool # (/=) :: InjectivityAnn -> InjectivityAnn -> Bool # | |
Eq Overlap | |
Eq () | |
Eq TyCon | |
Eq Module | |
Eq TrName | |
Eq Version | Since: base-2.1 |
Eq StdGen | |
Eq Void | Since: base-4.8.0.0 |
Eq SpecConstrAnnotation | Since: base-4.3.0.0 |
Defined in GHC.Exts Methods (==) :: SpecConstrAnnotation -> SpecConstrAnnotation -> Bool # (/=) :: SpecConstrAnnotation -> SpecConstrAnnotation -> Bool # | |
Eq Unique | |
Eq ThreadId | Since: base-4.2.0.0 |
Eq BlockReason | Since: base-4.3.0.0 |
Defined in GHC.Conc.Sync | |
Eq ThreadStatus | Since: base-4.3.0.0 |
Defined in GHC.Conc.Sync | |
Eq AsyncException | Since: base-4.2.0.0 |
Defined in GHC.IO.Exception Methods (==) :: AsyncException -> AsyncException -> Bool # (/=) :: AsyncException -> AsyncException -> Bool # | |
Eq ArrayException | Since: base-4.2.0.0 |
Defined in GHC.IO.Exception Methods (==) :: ArrayException -> ArrayException -> Bool # (/=) :: ArrayException -> ArrayException -> Bool # | |
Eq ExitCode | |
Eq IOErrorType | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception | |
Eq MaskingState | Since: base-4.3.0.0 |
Defined in GHC.IO | |
Eq IOException | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception | |
Eq All | Since: base-2.1 |
Eq Any | Since: base-2.1 |
Eq Fixity | Since: base-4.6.0.0 |
Eq Associativity | Since: base-4.6.0.0 |
Defined in GHC.Generics Methods (==) :: Associativity -> Associativity -> Bool # (/=) :: Associativity -> Associativity -> Bool # | |
Eq SourceUnpackedness | Since: base-4.9.0.0 |
Defined in GHC.Generics Methods (==) :: SourceUnpackedness -> SourceUnpackedness -> Bool # (/=) :: SourceUnpackedness -> SourceUnpackedness -> Bool # | |
Eq SourceStrictness | Since: base-4.9.0.0 |
Defined in GHC.Generics Methods (==) :: SourceStrictness -> SourceStrictness -> Bool # (/=) :: SourceStrictness -> SourceStrictness -> Bool # | |
Eq DecidedStrictness | Since: base-4.9.0.0 |
Defined in GHC.Generics Methods (==) :: DecidedStrictness -> DecidedStrictness -> Bool # (/=) :: DecidedStrictness -> DecidedStrictness -> Bool # | |
Eq CChar | |
Eq CSChar | |
Eq CUChar | |
Eq CShort | |
Eq CUShort | |
Eq CInt | |
Eq CUInt | |
Eq CLong | |
Eq CULong | |
Eq CLLong | |
Eq CULLong | |
Eq CBool | |
Eq CFloat | |
Eq CDouble | |
Eq CPtrdiff | |
Eq CSize | |
Eq CWchar | |
Eq CSigAtomic | |
Defined in Foreign.C.Types | |
Eq CClock | |
Eq CTime | |
Eq CUSeconds | |
Eq CSUSeconds | |
Defined in Foreign.C.Types | |
Eq CIntPtr | |
Eq CUIntPtr | |
Eq CIntMax | |
Eq CUIntMax | |
Eq Fingerprint | Since: base-4.4.0.0 |
Defined in GHC.Fingerprint.Type | |
Eq Lexeme | Since: base-2.1 |
Eq Number | Since: base-4.6.0.0 |
Eq GeneralCategory | Since: base-2.1 |
Defined in GHC.Unicode Methods (==) :: GeneralCategory -> GeneralCategory -> Bool # (/=) :: GeneralCategory -> GeneralCategory -> Bool # | |
Eq SrcLoc | Since: base-4.9.0.0 |
Eq IntSet | |
Eq Extension | |
Eq ForeignSrcLang | |
Defined in GHC.ForeignSrcLang.Type Methods (==) :: ForeignSrcLang -> ForeignSrcLang -> Bool # (/=) :: ForeignSrcLang -> ForeignSrcLang -> Bool # | |
Eq BigNat | |
Eq Message | |
Eq ParseError | |
Defined in Text.Parsec.Error | |
Eq SourcePos | |
Eq Doc | |
Eq TextDetails | |
Defined in Text.PrettyPrint.Annotated.HughesPJ | |
Eq Style | |
Eq Mode | |
Eq ModName | |
Eq PkgName | |
Eq Module | |
Eq OccName | |
Eq NameFlavour | |
Defined in Language.Haskell.TH.Syntax | |
Eq NameSpace | |
Eq Loc | |
Eq Info | |
Eq ModuleInfo | |
Defined in Language.Haskell.TH.Syntax | |
Eq Fixity | |
Eq FixityDirection | |
Defined in Language.Haskell.TH.Syntax Methods (==) :: FixityDirection -> FixityDirection -> Bool # (/=) :: FixityDirection -> FixityDirection -> Bool # | |
Eq Lit | |
Eq Bytes | |
Eq Body | |
Eq Guard | |
Eq Stmt | |
Eq Range | |
Eq DerivClause | |
Defined in Language.Haskell.TH.Syntax | |
Eq DerivStrategy | |
Defined in Language.Haskell.TH.Syntax Methods (==) :: DerivStrategy -> DerivStrategy -> Bool # (/=) :: DerivStrategy -> DerivStrategy -> Bool # | |
Eq TypeFamilyHead | |
Defined in Language.Haskell.TH.Syntax Methods (==) :: TypeFamilyHead -> TypeFamilyHead -> Bool # (/=) :: TypeFamilyHead -> TypeFamilyHead -> Bool # | |
Eq TySynEqn | |
Eq Foreign | |
Eq Callconv | |
Eq Safety | |
Eq Pragma | |
Eq Inline | |
Eq RuleMatch | |
Eq Phases | |
Eq RuleBndr | |
Eq AnnTarget | |
Eq SourceUnpackedness | |
Defined in Language.Haskell.TH.Syntax Methods (==) :: SourceUnpackedness -> SourceUnpackedness -> Bool # (/=) :: SourceUnpackedness -> SourceUnpackedness -> Bool # | |
Eq SourceStrictness | |
Defined in Language.Haskell.TH.Syntax Methods (==) :: SourceStrictness -> SourceStrictness -> Bool # (/=) :: SourceStrictness -> SourceStrictness -> Bool # | |
Eq DecidedStrictness | |
Defined in Language.Haskell.TH.Syntax Methods (==) :: DecidedStrictness -> DecidedStrictness -> Bool # (/=) :: DecidedStrictness -> DecidedStrictness -> Bool # | |
Eq Con | |
Eq Bang | |
Eq PatSynDir | |
Eq PatSynArgs | |
Defined in Language.Haskell.TH.Syntax | |
Eq TyVarBndr | |
Eq FamilyResultSig | |
Defined in Language.Haskell.TH.Syntax Methods (==) :: FamilyResultSig -> FamilyResultSig -> Bool # (/=) :: FamilyResultSig -> FamilyResultSig -> Bool # | |
Eq TyLit | |
Eq Role | |
Eq AnnLookup | |
Eq T Source # | |
Eq T Source # | |
Eq T Source # | |
Eq T Source # | |
Eq Dimension Source # | |
Eq a => Eq [a] | |
Eq a => Eq (Maybe a) | Since: base-2.1 |
Eq a => Eq (Ratio a) | Since: base-2.1 |
Eq (StablePtr a) | Since: base-2.1 |
Eq (Ptr a) | Since: base-2.1 |
Eq (FunPtr a) | |
Eq p => Eq (Par1 p) | Since: base-4.7.0.0 |
Eq a => Eq (Complex a) | Since: base-2.1 |
Eq a => Eq (Min a) | Since: base-4.9.0.0 |
Eq a => Eq (Max a) | Since: base-4.9.0.0 |
Eq a => Eq (First a) | Since: base-4.9.0.0 |
Eq a => Eq (Last a) | Since: base-4.9.0.0 |
Eq m => Eq (WrappedMonoid m) | Since: base-4.9.0.0 |
Defined in Data.Semigroup Methods (==) :: WrappedMonoid m -> WrappedMonoid m -> Bool # (/=) :: WrappedMonoid m -> WrappedMonoid m -> Bool # | |
Eq a => Eq (Option a) | Since: base-4.9.0.0 |
Eq (StableName a) | Since: base-2.1 |
Defined in GHC.StableName | |
Eq a => Eq (ZipList a) | Since: base-4.7.0.0 |
Eq a => Eq (Identity a) | Since: base-4.8.0.0 |
Eq (TVar a) | Since: base-4.8.0.0 |
Eq (IORef a) | Pointer equality. Since: base-4.0.0.0 |
Eq a => Eq (First a) | Since: base-2.1 |
Eq a => Eq (Last a) | Since: base-2.1 |
Eq a => Eq (Dual a) | Since: base-2.1 |
Eq a => Eq (Sum a) | Since: base-2.1 |
Eq a => Eq (Product a) | Since: base-2.1 |
Eq a => Eq (Down a) | Since: base-4.6.0.0 |
Eq (MVar a) | Since: base-4.1.0.0 |
Eq a => Eq (NonEmpty a) | Since: base-4.9.0.0 |
Eq a => Eq (IntMap a) | |
Eq a => Eq (Tree a) | |
Eq a => Eq (Seq a) | |
Eq a => Eq (ViewL a) | |
Eq a => Eq (ViewR a) | |
Eq a => Eq (Set a) | |
Eq a => Eq (T a) | |
C a => Eq (T a) | |
Eq (Doc a) | |
Eq a => Eq (AnnotDetails a) | |
Defined in Text.PrettyPrint.Annotated.HughesPJ Methods (==) :: AnnotDetails a -> AnnotDetails a -> Bool # (/=) :: AnnotDetails a -> AnnotDetails a -> Bool # | |
Eq a => Eq (Span a) | |
Eq g => Eq (StateGen g) | |
Eq a => Eq (ToOrd a) Source # | |
Eq a => Eq (Max a) Source # | |
Eq a => Eq (Min a) Source # | |
Eq a => Eq (LCM a) Source # | |
Eq a => Eq (GCD a) Source # | |
Eq a => Eq (T a) Source # | |
Eq a => Eq (T a) Source # | |
(Eq a, C a, C a) => Eq (T a) Source # | |
Eq (T a) Source # | |
Eq a => Eq (T a) Source # | |
Eq a => Eq (Valuable a) Source # | |
Eq a => Eq (T a) Source # | |
C a => Eq (T a) Source # | |
(Eq a, C a) => Eq (T a) Source # | |
(Eq a, C a) => Eq (T a) Source # | |
(Eq a, C a) => Eq (T a) Source # | |
(Eq a, C a) => Eq (T a) Source # | |
Ix i => Eq (T i) Source # | These instances may need more work They involve converting a permutation to a table. |
Eq i => Eq (Cycle i) Source # | |
Eq a => Eq (T a) Source # | |
Eq a => Eq (T a) Source # | |
Eq a => Eq (T a) Source # | |
Eq a => Eq (T a) Source # | |
(Eq a, C a) => Eq (T a) Source # | |
Eq a => Eq (T a) Source # | |
(Eq a, Eq b) => Eq (Either a b) | Since: base-2.1 |
Eq (V1 p) | Since: base-4.9.0.0 |
Eq (U1 p) | Since: base-4.9.0.0 |
Eq (TypeRep a) | Since: base-2.1 |
(Eq a, Eq b) => Eq (a, b) | |
(Ix i, Eq e) => Eq (Array i e) | Since: base-2.1 |
Eq (Fixed a) | Since: base-2.1 |
Eq a => Eq (Arg a b) | Since: base-4.9.0.0 |
Eq (Proxy s) | Since: base-4.7.0.0 |
Eq (STRef s a) | Pointer equality. Since: base-2.1 |
(Eq k, Eq a) => Eq (Map k a) | |
(Eq a, Eq b) => Eq (T a b) Source # | |
Eq v => Eq (T a v) Source # | |
Eq a => Eq (T u a) Source # | |
(Eq i, Eq a) => Eq (T i a) Source # | |
Eq v => Eq (T a v) Source # | |
Eq (f p) => Eq (Rec1 f p) | Since: base-4.7.0.0 |
Eq (URec (Ptr ()) p) | Since: base-4.9.0.0 |
Eq (URec Char p) | Since: base-4.9.0.0 |
Eq (URec Double p) | Since: base-4.9.0.0 |
Eq (URec Float p) | |
Eq (URec Int p) | Since: base-4.9.0.0 |
Eq (URec Word p) | Since: base-4.9.0.0 |
(Eq a, Eq b, Eq c) => Eq (a, b, c) | |
Eq (STArray s i e) | Since: base-2.1 |
Eq a => Eq (Const a b) | Since: base-4.9.0.0 |
Eq (f a) => Eq (Ap f a) | Since: base-4.12.0.0 |
Eq (f a) => Eq (Alt f a) | Since: base-4.8.0.0 |
Eq (a :~: b) | Since: base-4.7.0.0 |
(Eq e, Eq1 m, Eq a) => Eq (ErrorT e m a) | |
Eq a => Eq (Constant a b) | |
Eq c => Eq (K1 i c p) | Since: base-4.7.0.0 |
(Eq (f p), Eq (g p)) => Eq ((f :+: g) p) | Since: base-4.7.0.0 |
(Eq (f p), Eq (g p)) => Eq ((f :*: g) p) | Since: base-4.7.0.0 |
(Eq a, Eq b, Eq c, Eq d) => Eq (a, b, c, d) | |
(Eq1 f, Eq1 g, Eq a) => Eq (Product f g a) | Since: base-4.9.0.0 |
(Eq1 f, Eq1 g, Eq a) => Eq (Sum f g a) | Since: base-4.9.0.0 |
Eq (a :~~: b) | Since: base-4.10.0.0 |
Eq (f p) => Eq (M1 i c f p) | Since: base-4.7.0.0 |
Eq (f (g p)) => Eq ((f :.: g) p) | Since: base-4.7.0.0 |
(Eq a, Eq b, Eq c, Eq d, Eq e) => Eq (a, b, c, d, e) | |
(Eq1 f, Eq1 g, Eq a) => Eq (Compose f g a) | Since: base-4.9.0.0 |
(Eq a, Eq b, Eq c, Eq d, Eq e, Eq f) => Eq (a, b, c, d, e, f) | |
(Eq a, Eq b, Eq c, Eq d, Eq e, Eq f, Eq g) => Eq (a, b, c, d, e, f, g) | |
(Eq a, Eq b, Eq c, Eq d, Eq e, Eq f, Eq g, Eq h) => Eq (a, b, c, d, e, f, g, h) | |
(Eq a, Eq b, Eq c, Eq d, Eq e, Eq f, Eq g, Eq h, Eq i) => Eq (a, b, c, d, e, f, g, h, i) | |
(Eq a, Eq b, Eq c, Eq d, Eq e, Eq f, Eq g, Eq h, Eq i, Eq j) => Eq (a, b, c, d, e, f, g, h, i, j) | |
(Eq a, Eq b, Eq c, Eq d, Eq e, Eq f, Eq g, Eq h, Eq i, Eq j, Eq k) => Eq (a, b, c, d, e, f, g, h, i, j, k) | |
(Eq a, Eq b, Eq c, Eq d, Eq e, Eq f, Eq g, Eq h, Eq i, Eq j, Eq k, Eq l) => Eq (a, b, c, d, e, f, g, h, i, j, k, l) | |
(Eq a, Eq b, Eq c, Eq d, Eq e, Eq f, Eq g, Eq h, Eq i, Eq j, Eq k, Eq l, Eq m) => Eq (a, b, c, d, e, f, g, h, i, j, k, l, m) | |
(Eq a, Eq b, Eq c, Eq d, Eq e, Eq f, Eq g, Eq h, Eq i, Eq j, Eq k, Eq l, Eq m, Eq n) => Eq (a, b, c, d, e, f, g, h, i, j, k, l, m, n) | |
(Eq a, Eq b, Eq c, Eq d, Eq e, Eq f, Eq g, Eq h, Eq i, Eq j, Eq k, Eq l, Eq m, Eq n, Eq o) => Eq (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) | |
File and directory names are values of type String
, whose precise
meaning is operating system dependent. Files can be opened, yielding a
handle which can then be used to operate on the contents of that file.
class Functor (f :: Type -> Type) where #
A type f
is a Functor if it provides a function fmap
which, given any types a
and b
lets you apply any function from (a -> b)
to turn an f a
into an f b
, preserving the
structure of f
. Furthermore f
needs to adhere to the following:
Note, that the second law follows from the free theorem of the type fmap
and
the first law, so you need only check that the former condition holds.
Minimal complete definition
Methods
fmap :: (a -> b) -> f a -> f b #
Using ApplicativeDo
: '
' can be understood as
the fmap
f asdo
expression
do a <- as pure (f a)
with an inferred Functor
constraint.