pa-prelude-0.1.0.0: The Possehl Analytics Prelude
Safe HaskellSafe-Inferred
LanguageGHC2021

PossehlAnalyticsPrelude

Synopsis

Text conversions

data Text #

A space efficient, packed, unboxed Unicode text type.

Instances

Instances details
PyFToString Text 
Instance details

Defined in PyF.Class

Methods

pyfToString :: Text -> String #

Hashable Text 
Instance details

Defined in Data.Hashable.Class

Methods

hashWithSalt :: Int -> Text -> Int #

hash :: Text -> Int #

type PyFClassify Text 
Instance details

Defined in PyF.Class

type Item Text 
Instance details

Defined in Data.Text

type Item Text = Char

data ByteString #

A space-efficient representation of a Word8 vector, supporting many efficient operations.

A ByteString contains 8-bit bytes, or by using the operations from Data.ByteString.Char8 it can be interpreted as containing 8-bit characters.

Instances

Instances details
PyFToString ByteString 
Instance details

Defined in PyF.Class

Data ByteString 
Instance details

Defined in Data.ByteString.Internal

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> ByteString -> c ByteString #

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c ByteString #

toConstr :: ByteString -> Constr #

dataTypeOf :: ByteString -> DataType #

dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c ByteString) #

dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c ByteString) #

gmapT :: (forall b. Data b => b -> b) -> ByteString -> ByteString #

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> ByteString -> r #

gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> ByteString -> r #

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

gmapQi :: Int -> (forall d. Data d => d -> u) -> ByteString -> u #

gmapM :: Monad m => (forall d. Data d => d -> m d) -> ByteString -> m ByteString #

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> ByteString -> m ByteString #

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> ByteString -> m ByteString #

IsString ByteString

Beware: fromString truncates multi-byte characters to octets. e.g. "枯朶に烏のとまりけり秋の暮" becomes �6k�nh~�Q��n�

Instance details

Defined in Data.ByteString.Internal

Monoid ByteString 
Instance details

Defined in Data.ByteString.Internal

Semigroup ByteString 
Instance details

Defined in Data.ByteString.Internal

IsList ByteString

Since: bytestring-0.10.12.0

Instance details

Defined in Data.ByteString.Internal

Associated Types

type Item ByteString #

Read ByteString 
Instance details

Defined in Data.ByteString.Internal

Show ByteString 
Instance details

Defined in Data.ByteString.Internal

NFData ByteString 
Instance details

Defined in Data.ByteString.Internal

Methods

rnf :: ByteString -> () #

Eq ByteString 
Instance details

Defined in Data.ByteString.Internal

Ord ByteString 
Instance details

Defined in Data.ByteString.Internal

Hashable ByteString 
Instance details

Defined in Data.Hashable.Class

Lift ByteString

Since: bytestring-0.11.2.0

Instance details

Defined in Data.ByteString.Internal

Methods

lift :: Quote m => ByteString -> m Exp #

liftTyped :: forall (m :: Type -> Type). Quote m => ByteString -> Code m ByteString #

type PyFClassify ByteString 
Instance details

Defined in PyF.Class

type Item ByteString 
Instance details

Defined in Data.ByteString.Internal

data Word8 #

8-bit unsigned integer type

Instances

Instances details
Data Word8

Since: base-4.0.0.0

Instance details

Defined in Data.Data

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Word8 -> c Word8 #

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c Word8 #

toConstr :: Word8 -> Constr #

dataTypeOf :: Word8 -> DataType #

dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c Word8) #

dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c Word8) #

gmapT :: (forall b. Data b => b -> b) -> Word8 -> Word8 #

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Word8 -> r #

gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Word8 -> r #

gmapQ :: (forall d. Data d => d -> u) -> Word8 -> [u] #

gmapQi :: Int -> (forall d. Data d => d -> u) -> Word8 -> u #

gmapM :: Monad m => (forall d. Data d => d -> m d) -> Word8 -> m Word8 #

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Word8 -> m Word8 #

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Word8 -> m Word8 #

Bits Word8

Since: base-2.1

Instance details

Defined in GHC.Word

FiniteBits Word8

Since: base-4.6.0.0

Instance details

Defined in GHC.Word

Bounded Word8

Since: base-2.1

Instance details

Defined in GHC.Word

Enum Word8

Since: base-2.1

Instance details

Defined in GHC.Word

Ix Word8

Since: base-2.1

Instance details

Defined in GHC.Word

Num Word8

Since: base-2.1

Instance details

Defined in GHC.Word

Read Word8

Since: base-2.1

Instance details

Defined in GHC.Read

Integral Word8

Since: base-2.1

Instance details

Defined in GHC.Word

Real Word8

Since: base-2.1

Instance details

Defined in GHC.Word

Methods

toRational :: Word8 -> Rational #

Show Word8

Since: base-2.1

Instance details

Defined in GHC.Word

Methods

showsPrec :: Int -> Word8 -> ShowS #

show :: Word8 -> String #

showList :: [Word8] -> ShowS #

Eq Word8

Since: base-2.1

Instance details

Defined in GHC.Word

Methods

(==) :: Word8 -> Word8 -> Bool #

(/=) :: Word8 -> Word8 -> Bool #

Ord Word8

Since: base-2.1

Instance details

Defined in GHC.Word

Methods

compare :: Word8 -> Word8 -> Ordering #

(<) :: Word8 -> Word8 -> Bool #

(<=) :: Word8 -> Word8 -> Bool #

(>) :: Word8 -> Word8 -> Bool #

(>=) :: Word8 -> Word8 -> Bool #

max :: Word8 -> Word8 -> Word8 #

min :: Word8 -> Word8 -> Word8 #

Hashable Word8 
Instance details

Defined in Data.Hashable.Class

Methods

hashWithSalt :: Int -> Word8 -> Int #

hash :: Word8 -> Int #

IArray UArray Word8 
Instance details

Defined in Data.Array.Base

Methods

bounds :: Ix i => UArray i Word8 -> (i, i) #

numElements :: Ix i => UArray i Word8 -> Int

unsafeArray :: Ix i => (i, i) -> [(Int, Word8)] -> UArray i Word8

unsafeAt :: Ix i => UArray i Word8 -> Int -> Word8

unsafeReplace :: Ix i => UArray i Word8 -> [(Int, Word8)] -> UArray i Word8

unsafeAccum :: Ix i => (Word8 -> e' -> Word8) -> UArray i Word8 -> [(Int, e')] -> UArray i Word8

unsafeAccumArray :: Ix i => (Word8 -> e' -> Word8) -> Word8 -> (i, i) -> [(Int, e')] -> UArray i Word8

Lift Word8 
Instance details

Defined in Language.Haskell.TH.Syntax

Methods

lift :: Quote m => Word8 -> m Exp #

liftTyped :: forall (m :: Type -> Type). Quote m => Word8 -> Code m Word8 #

MArray (STUArray s) Word8 (ST s) 
Instance details

Defined in Data.Array.Base

Methods

getBounds :: Ix i => STUArray s i Word8 -> ST s (i, i) #

getNumElements :: Ix i => STUArray s i Word8 -> ST s Int

newArray :: Ix i => (i, i) -> Word8 -> ST s (STUArray s i Word8) #

newArray_ :: Ix i => (i, i) -> ST s (STUArray s i Word8) #

unsafeNewArray_ :: Ix i => (i, i) -> ST s (STUArray s i Word8)

unsafeRead :: Ix i => STUArray s i Word8 -> Int -> ST s Word8

unsafeWrite :: Ix i => STUArray s i Word8 -> Int -> Word8 -> ST s ()

type PyFClassify Word8 
Instance details

Defined in PyF.Class

fmt :: QuasiQuoter #

Generic formatter, can format an expression to any t as long as t is an instance of IsString.

showToText :: Show a => a -> Text Source #

textToBytesUtf8 :: Text -> ByteString Source #

encode a Text to a UTF-8 encoded Bytestring

textToBytesUtf8Lazy :: Text -> ByteString Source #

encode a lazy Text to a UTF-8 encoded lazy Bytestring

bytesToTextUtf8Lenient :: ByteString -> Text Source #

decode a Text from a ByteString that is assumed to be UTF-8, replace non-UTF-8 characters with the replacment char U+FFFD.

bytesToTextUtf8LenientLazy :: ByteString -> Text Source #

decode a lazy Text from a lazy ByteString that is assumed to be UTF-8, replace non-UTF-8 characters with the replacment char U+FFFD.

bytesToTextUtf8Unsafe :: ByteString -> Text Source #

decode a Text from a ByteString that is assumed to be UTF-8 (crash if that is not the case)

bytesToTextUtf8UnsafeLazy :: ByteString -> Text Source #

decode a Text from a ByteString that is assumed to be UTF-8 (crash if that is not the case)

toStrict :: Text -> Text Source #

Make a lazy text strict

toLazy :: Text -> Text Source #

Make a strict text lazy

charToWordUnsafe :: Char -> Word8 Source #

Unsafe conversion between Char and Word8. This is a no-op and silently truncates to 8 bits Chars > '255'. It is provided as convenience for ByteString construction.

Use if you want to get the Word8 representation of a character literal. Don’t use on arbitrary characters!

>>> charToWordUnsafe ','
44

IO

putStrLn :: String -> IO () #

The same as putStr, but adds a newline character.

putStderrLn :: Text -> IO () Source #

Put the text to stderr.

WIP code

todo :: forall (r :: RuntimeRep). forall (a :: TYPE r). HasCallStack => a Source #

Warning: todo (undefined code) remains in code

Use this in places where the code is still to be implemented.

It always type-checks and will show a warning at compile time if it was forgotten in the code.

Use instead of error and undefined for code that hasn’t been written.

Uses the same trick as https://hackage.haskell.org/package/protolude-0.3.0/docs/src/Protolude.Error.html#error

Records

class HasField (x :: k) r a | x r -> a #

Constraint representing the fact that the field x belongs to the record type r and has field type a. This will be solved automatically, but manual instances may be provided as well.

Minimal complete definition

getField

Control flow

doAs :: forall m a. m a -> m a Source #

Mark a `do`-block with the type of the Monad/Applicativ it uses. Only intended for reading ease and making code easier to understand, especially do-blocks that use unconventional monads (like Maybe or List).

Example:

doAs @Maybe $ do
 a <- Just a
 b <- Just b
 pure (a, b)

(&) :: a -> (a -> b) -> b infixl 1 #

& is a reverse application operator. This provides notational convenience. Its precedence is one higher than that of the forward application operator $, which allows & to be nested in $.

>>> 5 & (+1) & show
"6"

Since: base-4.8.0.0

(<&>) :: Functor f => f a -> (a -> b) -> f b infixl 1 #

Flipped version of <$>.

(<&>) = flip fmap

Examples

Expand

Apply (+1) to a list, a Just and a Right:

>>> Just 2 <&> (+1)
Just 3
>>> [1,2,3] <&> (+1)
[2,3,4]
>>> Right 3 <&> (+1)
Right 4

Since: base-4.11.0.0

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

An associative binary operation

foldMap1 :: (Foldable1 t, Semigroup m) => (a -> m) -> t a -> m #

Map each element of the structure to a semigroup, and combine the results.

>>> foldMap1 Sum (1 :| [2, 3, 4])
Sum {getSum = 10}

foldMap' :: (Foldable t, Monoid m) => (a -> m) -> t a -> m #

A left-associative variant of foldMap that is strict in the accumulator. Use this method for strict reduction when partial results are merged via (<>).

Examples

Expand

Define a Monoid over finite bit strings under xor. Use it to strictly compute the xor of a list of Int values.

>>> :set -XGeneralizedNewtypeDeriving
>>> import Data.Bits (Bits, FiniteBits, xor, zeroBits)
>>> import Data.Foldable (foldMap')
>>> import Numeric (showHex)
>>> 
>>> newtype X a = X a deriving (Eq, Bounded, Enum, Bits, FiniteBits)
>>> instance Bits a => Semigroup (X a) where X a <> X b = X (a `xor` b)
>>> instance Bits a => Monoid    (X a) where mempty     = X zeroBits
>>> 
>>> let bits :: [Int]; bits = [0xcafe, 0xfeed, 0xdeaf, 0xbeef, 0x5411]
>>> (\ (X a) -> showString "0x" . showHex a $ "") $ foldMap' X bits
"0x42"

Since: base-4.13.0.0

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

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.

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

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.

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

The reverse of when.

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

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)

newtype ExceptT e (m :: Type -> Type) a #

A monad transformer that adds exceptions to other monads.

ExceptT constructs a monad parameterized over two things:

  • e - The exception type.
  • m - The inner monad.

The return function yields a computation that produces the given value, while >>= sequences two subcomputations, exiting on the first exception.

Constructors

ExceptT (m (Either e a)) 

Instances

Instances details
MonadReader r m => MonadReader r (ExceptT e m)

Since: mtl-2.2

Instance details

Defined in Control.Monad.Reader.Class

Methods

ask :: ExceptT e m r #

local :: (r -> r) -> ExceptT e m a -> ExceptT e m a #

reader :: (r -> a) -> ExceptT e m a #

MonadTrans (ExceptT e) 
Instance details

Defined in Control.Monad.Trans.Except

Methods

lift :: Monad m => m a -> ExceptT e m a #

MonadFail m => MonadFail (ExceptT e m) 
Instance details

Defined in Control.Monad.Trans.Except

Methods

fail :: String -> ExceptT e m a #

MonadFix m => MonadFix (ExceptT e m) 
Instance details

Defined in Control.Monad.Trans.Except

Methods

mfix :: (a -> ExceptT e m a) -> ExceptT e m a #

MonadIO m => MonadIO (ExceptT e m) 
Instance details

Defined in Control.Monad.Trans.Except

Methods

liftIO :: IO a -> ExceptT e m a #

MonadZip m => MonadZip (ExceptT e m) 
Instance details

Defined in Control.Monad.Trans.Except

Methods

mzip :: ExceptT e m a -> ExceptT e m b -> ExceptT e m (a, b) #

mzipWith :: (a -> b -> c) -> ExceptT e m a -> ExceptT e m b -> ExceptT e m c #

munzip :: ExceptT e m (a, b) -> (ExceptT e m a, ExceptT e m b) #

Foldable f => Foldable (ExceptT e f) 
Instance details

Defined in Control.Monad.Trans.Except

Methods

fold :: Monoid m => ExceptT e f m -> m #

foldMap :: Monoid m => (a -> m) -> ExceptT e f a -> m #

foldMap' :: Monoid m => (a -> m) -> ExceptT e f a -> m #

foldr :: (a -> b -> b) -> b -> ExceptT e f a -> b #

foldr' :: (a -> b -> b) -> b -> ExceptT e f a -> b #

foldl :: (b -> a -> b) -> b -> ExceptT e f a -> b #

foldl' :: (b -> a -> b) -> b -> ExceptT e f a -> b #

foldr1 :: (a -> a -> a) -> ExceptT e f a -> a #

foldl1 :: (a -> a -> a) -> ExceptT e f a -> a #

toList :: ExceptT e f a -> [a] #

null :: ExceptT e f a -> Bool #

length :: ExceptT e f a -> Int #

elem :: Eq a => a -> ExceptT e f a -> Bool #

maximum :: Ord a => ExceptT e f a -> a #

minimum :: Ord a => ExceptT e f a -> a #

sum :: Num a => ExceptT e f a -> a #

product :: Num a => ExceptT e f a -> a #

(Eq e, Eq1 m) => Eq1 (ExceptT e m) 
Instance details

Defined in Control.Monad.Trans.Except

Methods

liftEq :: (a -> b -> Bool) -> ExceptT e m a -> ExceptT e m b -> Bool #

(Ord e, Ord1 m) => Ord1 (ExceptT e m) 
Instance details

Defined in Control.Monad.Trans.Except

Methods

liftCompare :: (a -> b -> Ordering) -> ExceptT e m a -> ExceptT e m b -> Ordering #

(Read e, Read1 m) => Read1 (ExceptT e m) 
Instance details

Defined in Control.Monad.Trans.Except

Methods

liftReadsPrec :: (Int -> ReadS a) -> ReadS [a] -> Int -> ReadS (ExceptT e m a) #

liftReadList :: (Int -> ReadS a) -> ReadS [a] -> ReadS [ExceptT e m a] #

liftReadPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec (ExceptT e m a) #

liftReadListPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec [ExceptT e m a] #

(Show e, Show1 m) => Show1 (ExceptT e m) 
Instance details

Defined in Control.Monad.Trans.Except

Methods

liftShowsPrec :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> Int -> ExceptT e m a -> ShowS #

liftShowList :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> [ExceptT e m a] -> ShowS #

Contravariant m => Contravariant (ExceptT e m) 
Instance details

Defined in Control.Monad.Trans.Except

Methods

contramap :: (a' -> a) -> ExceptT e m a -> ExceptT e m a' #

(>$) :: b -> ExceptT e m b -> ExceptT e m a #

Traversable f => Traversable (ExceptT e f) 
Instance details

Defined in Control.Monad.Trans.Except

Methods

traverse :: Applicative f0 => (a -> f0 b) -> ExceptT e f a -> f0 (ExceptT e f b) #

sequenceA :: Applicative f0 => ExceptT e f (f0 a) -> f0 (ExceptT e f a) #

mapM :: Monad m => (a -> m b) -> ExceptT e f a -> m (ExceptT e f b) #

sequence :: Monad m => ExceptT e f (m a) -> m (ExceptT e f a) #

(Functor m, Monad m, Monoid e) => Alternative (ExceptT e m) 
Instance details

Defined in Control.Monad.Trans.Except

Methods

empty :: ExceptT e m a #

(<|>) :: ExceptT e m a -> ExceptT e m a -> ExceptT e m a #

some :: ExceptT e m a -> ExceptT e m [a] #

many :: ExceptT e m a -> ExceptT e m [a] #

(Functor m, Monad m) => Applicative (ExceptT e m) 
Instance details

Defined in Control.Monad.Trans.Except

Methods

pure :: a -> ExceptT e m a #

(<*>) :: ExceptT e m (a -> b) -> ExceptT e m a -> ExceptT e m b #

liftA2 :: (a -> b -> c) -> ExceptT e m a -> ExceptT e m b -> ExceptT e m c #

(*>) :: ExceptT e m a -> ExceptT e m b -> ExceptT e m b #

(<*) :: ExceptT e m a -> ExceptT e m b -> ExceptT e m a #

Functor m => Functor (ExceptT e m) 
Instance details

Defined in Control.Monad.Trans.Except

Methods

fmap :: (a -> b) -> ExceptT e m a -> ExceptT e m b #

(<$) :: a -> ExceptT e m b -> ExceptT e m a #

Monad m => Monad (ExceptT e m) 
Instance details

Defined in Control.Monad.Trans.Except

Methods

(>>=) :: ExceptT e m a -> (a -> ExceptT e m b) -> ExceptT e m b #

(>>) :: ExceptT e m a -> ExceptT e m b -> ExceptT e m b #

return :: a -> ExceptT e m a #

(Monad m, Monoid e) => MonadPlus (ExceptT e m) 
Instance details

Defined in Control.Monad.Trans.Except

Methods

mzero :: ExceptT e m a #

mplus :: ExceptT e m a -> ExceptT e m a -> ExceptT e m a #

MonadCatch m => MonadCatch (ExceptT e m)

Catches exceptions from the base monad.

Instance details

Defined in Control.Monad.Catch

Methods

catch :: Exception e0 => ExceptT e m a -> (e0 -> ExceptT e m a) -> ExceptT e m a #

MonadMask m => MonadMask (ExceptT e m)

Since: exceptions-0.9.0

Instance details

Defined in Control.Monad.Catch

Methods

mask :: ((forall a. ExceptT e m a -> ExceptT e m a) -> ExceptT e m b) -> ExceptT e m b #

uninterruptibleMask :: ((forall a. ExceptT e m a -> ExceptT e m a) -> ExceptT e m b) -> ExceptT e m b #

generalBracket :: ExceptT e m a -> (a -> ExitCase b -> ExceptT e m c) -> (a -> ExceptT e m b) -> ExceptT e m (b, c) #

MonadThrow m => MonadThrow (ExceptT e m)

Throws exceptions into the base monad.

Instance details

Defined in Control.Monad.Catch

Methods

throwM :: Exception e0 => e0 -> ExceptT e m a #

(Functor f, Monad f, Semigroup e) => Alt (ExceptT e f) 
Instance details

Defined in Data.Functor.Alt

Methods

(<!>) :: ExceptT e f a -> ExceptT e f a -> ExceptT e f a #

some :: Applicative (ExceptT e f) => ExceptT e f a -> ExceptT e f [a] #

many :: Applicative (ExceptT e f) => ExceptT e f a -> ExceptT e f [a] #

(Functor m, Monad m) => Apply (ExceptT e m) 
Instance details

Defined in Data.Functor.Bind.Class

Methods

(<.>) :: ExceptT e m (a -> b) -> ExceptT e m a -> ExceptT e m b #

(.>) :: ExceptT e m a -> ExceptT e m b -> ExceptT e m b #

(<.) :: ExceptT e m a -> ExceptT e m b -> ExceptT e m a #

liftF2 :: (a -> b -> c) -> ExceptT e m a -> ExceptT e m b -> ExceptT e m c #

(Functor m, Monad m) => Bind (ExceptT e m) 
Instance details

Defined in Data.Functor.Bind.Class

Methods

(>>-) :: ExceptT e m a -> (a -> ExceptT e m b) -> ExceptT e m b #

join :: ExceptT e m (ExceptT e m a) -> ExceptT e m a #

(Read e, Read1 m, Read a) => Read (ExceptT e m a) 
Instance details

Defined in Control.Monad.Trans.Except

Methods

readsPrec :: Int -> ReadS (ExceptT e m a) #

readList :: ReadS [ExceptT e m a] #

readPrec :: ReadPrec (ExceptT e m a) #

readListPrec :: ReadPrec [ExceptT e m a] #

(Show e, Show1 m, Show a) => Show (ExceptT e m a) 
Instance details

Defined in Control.Monad.Trans.Except

Methods

showsPrec :: Int -> ExceptT e m a -> ShowS #

show :: ExceptT e m a -> String #

showList :: [ExceptT e m a] -> ShowS #

(Eq e, Eq1 m, Eq a) => Eq (ExceptT e m a) 
Instance details

Defined in Control.Monad.Trans.Except

Methods

(==) :: ExceptT e m a -> ExceptT e m a -> Bool #

(/=) :: ExceptT e m a -> ExceptT e m a -> Bool #

(Ord e, Ord1 m, Ord a) => Ord (ExceptT e m a) 
Instance details

Defined in Control.Monad.Trans.Except

Methods

compare :: ExceptT e m a -> ExceptT e m a -> Ordering #

(<) :: ExceptT e m a -> ExceptT e m a -> Bool #

(<=) :: ExceptT e m a -> ExceptT e m a -> Bool #

(>) :: ExceptT e m a -> ExceptT e m a -> Bool #

(>=) :: ExceptT e m a -> ExceptT e m a -> Bool #

max :: ExceptT e m a -> ExceptT e m a -> ExceptT e m a #

min :: ExceptT e m a -> ExceptT e m a -> ExceptT e m a #

type Rep1 (ExceptT e m :: Type -> Type) 
Instance details

Defined in Control.Monad.Trans.Instances

type Rep1 (ExceptT e m :: Type -> Type) = D1 ('MetaData "ExceptT" "Control.Monad.Trans.Except" "transformers-0.5.6.2" 'True) (C1 ('MetaCons "ExceptT" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (m :.: Rec1 (Either e))))
type Rep (ExceptT e m a) 
Instance details

Defined in Control.Monad.Trans.Instances

type Rep (ExceptT e m a) = D1 ('MetaData "ExceptT" "Control.Monad.Trans.Except" "transformers-0.5.6.2" 'True) (C1 ('MetaCons "ExceptT" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 (m (Either e a)))))

runExceptT :: ExceptT e m a -> m (Either e a) #

The inverse of ExceptT.

class Monad m => MonadThrow (m :: Type -> Type) #

A class for monads in which exceptions may be thrown.

Instances should obey the following law:

throwM e >> x = throwM e

In other words, throwing an exception short-circuits the rest of the monadic computation.

Minimal complete definition

throwM

Instances

Instances details
MonadThrow STM 
Instance details

Defined in Control.Monad.Catch

Methods

throwM :: Exception e => e -> STM a #

MonadThrow IO 
Instance details

Defined in Control.Monad.Catch

Methods

throwM :: Exception e => e -> IO a #

MonadThrow Q 
Instance details

Defined in Control.Monad.Catch

Methods

throwM :: Exception e => e -> Q a #

MonadThrow Maybe 
Instance details

Defined in Control.Monad.Catch

Methods

throwM :: Exception e => e -> Maybe a #

MonadThrow [] 
Instance details

Defined in Control.Monad.Catch

Methods

throwM :: Exception e => e -> [a] #

e ~ SomeException => MonadThrow (Either e) 
Instance details

Defined in Control.Monad.Catch

Methods

throwM :: Exception e0 => e0 -> Either e a #

MonadThrow (ST s) 
Instance details

Defined in Control.Monad.Catch

Methods

throwM :: Exception e => e -> ST s a #

MonadThrow m => MonadThrow (ListT m) 
Instance details

Defined in Control.Monad.Catch

Methods

throwM :: Exception e => e -> ListT m a #

MonadThrow m => MonadThrow (MaybeT m)

Throws exceptions into the base monad.

Instance details

Defined in Control.Monad.Catch

Methods

throwM :: Exception e => e -> MaybeT m a #

(Error e, MonadThrow m) => MonadThrow (ErrorT e m)

Throws exceptions into the base monad.

Instance details

Defined in Control.Monad.Catch

Methods

throwM :: Exception e0 => e0 -> ErrorT e m a #

MonadThrow m => MonadThrow (ExceptT e m)

Throws exceptions into the base monad.

Instance details

Defined in Control.Monad.Catch

Methods

throwM :: Exception e0 => e0 -> ExceptT e m a #

MonadThrow m => MonadThrow (IdentityT m) 
Instance details

Defined in Control.Monad.Catch

Methods

throwM :: Exception e => e -> IdentityT m a #

MonadThrow m => MonadThrow (ReaderT r m) 
Instance details

Defined in Control.Monad.Catch

Methods

throwM :: Exception e => e -> ReaderT r m a #

MonadThrow m => MonadThrow (StateT s m) 
Instance details

Defined in Control.Monad.Catch

Methods

throwM :: Exception e => e -> StateT s m a #

MonadThrow m => MonadThrow (StateT s m) 
Instance details

Defined in Control.Monad.Catch

Methods

throwM :: Exception e => e -> StateT s m a #

(MonadThrow m, Monoid w) => MonadThrow (WriterT w m) 
Instance details

Defined in Control.Monad.Catch

Methods

throwM :: Exception e => e -> WriterT w m a #

(MonadThrow m, Monoid w) => MonadThrow (WriterT w m) 
Instance details

Defined in Control.Monad.Catch

Methods

throwM :: Exception e => e -> WriterT w m a #

MonadThrow m => MonadThrow (ContT r m) 
Instance details

Defined in Control.Monad.Catch

Methods

throwM :: Exception e => e -> ContT r m a #

(MonadThrow m, Monoid w) => MonadThrow (RWST r w s m) 
Instance details

Defined in Control.Monad.Catch

Methods

throwM :: Exception e => e -> RWST r w s m a #

(MonadThrow m, Monoid w) => MonadThrow (RWST r w s m) 
Instance details

Defined in Control.Monad.Catch

Methods

throwM :: Exception e => e -> RWST r w s m a #

throwM :: (MonadThrow m, Exception e) => e -> m a #

Throw an exception. Note that this throws when this action is run in the monad m, not when it is applied. It is a generalization of Control.Exception's throwIO.

Should satisfy the law:

throwM e >> f = throwM e

class Monad m => MonadIO (m :: Type -> Type) #

Monads in which IO computations may be embedded. Any monad built by applying a sequence of monad transformers to the IO monad will be an instance of this class.

Instances should satisfy the following laws, which state that liftIO is a transformer of monads:

Minimal complete definition

liftIO

Instances

Instances details
MonadIO IO

Since: base-4.9.0.0

Instance details

Defined in Control.Monad.IO.Class

Methods

liftIO :: IO a -> IO a #

MonadIO Q 
Instance details

Defined in Language.Haskell.TH.Syntax

Methods

liftIO :: IO a -> Q a #

(Error e, MonadIO m) => MonadIO (ErrorT e m) 
Instance details

Defined in Control.Monad.Trans.Error

Methods

liftIO :: IO a -> ErrorT e m a #

MonadIO m => MonadIO (ExceptT e m) 
Instance details

Defined in Control.Monad.Trans.Except

Methods

liftIO :: IO a -> ExceptT e m a #

MonadIO m => MonadIO (IdentityT m) 
Instance details

Defined in Control.Monad.Trans.Identity

Methods

liftIO :: IO a -> IdentityT m a #

liftIO :: MonadIO m => IO a -> m a #

Lift a computation from the IO monad. This allows us to run IO computations in any monadic stack, so long as it supports these kinds of operations (i.e. IO is the base monad for the stack).

Example

Expand
import Control.Monad.Trans.State -- from the "transformers" library

printState :: Show s => StateT s IO ()
printState = do
  state <- get
  liftIO $ print state

Had we omitted liftIO, we would have ended up with this error:

• Couldn't match type ‘IO’ with ‘StateT s IO’
 Expected type: StateT s IO ()
   Actual type: IO ()

The important part here is the mismatch between StateT s IO () and IO ().

Luckily, we know of a function that takes an IO a and returns an (m a): liftIO, enabling us to run the program and see the expected results:

> evalStateT printState "hello"
"hello"

> evalStateT printState 3
3

class Monad m => MonadReader r (m :: Type -> Type) | m -> r #

See examples in Control.Monad.Reader. Note, the partially applied function type (->) r is a simple reader monad. See the instance declaration below.

Minimal complete definition

(ask | reader), local

Instances

Instances details
MonadReader r m => MonadReader r (ListT m) 
Instance details

Defined in Control.Monad.Reader.Class

Methods

ask :: ListT m r #

local :: (r -> r) -> ListT m a -> ListT m a #

reader :: (r -> a) -> ListT m a #

MonadReader r m => MonadReader r (MaybeT m) 
Instance details

Defined in Control.Monad.Reader.Class

Methods

ask :: MaybeT m r #

local :: (r -> r) -> MaybeT m a -> MaybeT m a #

reader :: (r -> a) -> MaybeT m a #

(Error e, MonadReader r m) => MonadReader r (ErrorT e m) 
Instance details

Defined in Control.Monad.Reader.Class

Methods

ask :: ErrorT e m r #

local :: (r -> r) -> ErrorT e m a -> ErrorT e m a #

reader :: (r -> a) -> ErrorT e m a #

MonadReader r m => MonadReader r (ExceptT e m)

Since: mtl-2.2

Instance details

Defined in Control.Monad.Reader.Class

Methods

ask :: ExceptT e m r #

local :: (r -> r) -> ExceptT e m a -> ExceptT e m a #

reader :: (r -> a) -> ExceptT e m a #

MonadReader r m => MonadReader r (IdentityT m) 
Instance details

Defined in Control.Monad.Reader.Class

Methods

ask :: IdentityT m r #

local :: (r -> r) -> IdentityT m a -> IdentityT m a #

reader :: (r -> a) -> IdentityT m a #

Monad m => MonadReader r (ReaderT r m) 
Instance details

Defined in Control.Monad.Reader.Class

Methods

ask :: ReaderT r m r #

local :: (r -> r) -> ReaderT r m a -> ReaderT r m a #

reader :: (r -> a) -> ReaderT r m a #

MonadReader r m => MonadReader r (StateT s m) 
Instance details

Defined in Control.Monad.Reader.Class

Methods

ask :: StateT s m r #

local :: (r -> r) -> StateT s m a -> StateT s m a #

reader :: (r -> a) -> StateT s m a #

MonadReader r m => MonadReader r (StateT s m) 
Instance details

Defined in Control.Monad.Reader.Class

Methods

ask :: StateT s m r #

local :: (r -> r) -> StateT s m a -> StateT s m a #

reader :: (r -> a) -> StateT s m a #

(Monoid w, MonadReader r m) => MonadReader r (WriterT w m) 
Instance details

Defined in Control.Monad.Reader.Class

Methods

ask :: WriterT w m r #

local :: (r -> r) -> WriterT w m a -> WriterT w m a #

reader :: (r -> a) -> WriterT w m a #

(Monoid w, MonadReader r m) => MonadReader r (WriterT w m) 
Instance details

Defined in Control.Monad.Reader.Class

Methods

ask :: WriterT w m r #

local :: (r -> r) -> WriterT w m a -> WriterT w m a #

reader :: (r -> a) -> WriterT w m a #

MonadReader r ((->) r) 
Instance details

Defined in Control.Monad.Reader.Class

Methods

ask :: r -> r #

local :: (r -> r) -> (r -> a) -> r -> a #

reader :: (r -> a) -> r -> a #

MonadReader r' m => MonadReader r' (ContT r m) 
Instance details

Defined in Control.Monad.Reader.Class

Methods

ask :: ContT r m r' #

local :: (r' -> r') -> ContT r m a -> ContT r m a #

reader :: (r' -> a) -> ContT r m a #

(Monad m, Monoid w) => MonadReader r (RWST r w s m) 
Instance details

Defined in Control.Monad.Reader.Class

Methods

ask :: RWST r w s m r #

local :: (r -> r) -> RWST r w s m a -> RWST r w s m a #

reader :: (r -> a) -> RWST r w s m a #

(Monad m, Monoid w) => MonadReader r (RWST r w s m) 
Instance details

Defined in Control.Monad.Reader.Class

Methods

ask :: RWST r w s m r #

local :: (r -> r) -> RWST r w s m a -> RWST r w s m a #

reader :: (r -> a) -> RWST r w s m a #

asks #

Arguments

:: MonadReader r m 
=> (r -> a)

The selector function to apply to the environment.

-> m a 

Retrieves a function of the current environment.

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

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

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 #

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

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

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 #

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

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

Bifunctor These 
Instance details

Defined in Data.These

Methods

bimap :: (a -> b) -> (c -> d) -> These a c -> These b d #

first :: (a -> b) -> These a c -> These b c #

second :: (b -> c) -> These a b -> These a c #

Bifunctor Validation

Similar to Functor but allows mapping of values inside both Failure and Success.

Examples

>>> bimap length show (Success 50)
Success "50"
>>> bimap length show (Failure ["15", "9"])
Failure 2
Instance details

Defined in Validation

Methods

bimap :: (a -> b) -> (c -> d) -> Validation a c -> Validation b d #

first :: (a -> b) -> Validation a c -> Validation b c #

second :: (b -> c) -> Validation a b -> Validation a c #

Bifunctor (,)

Since: base-4.8.0.0

Instance details

Defined in Data.Bifunctor

Methods

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

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

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

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 #

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

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

Bifunctor (Tagged :: Type -> Type -> Type) 
Instance details

Defined in Data.Tagged

Methods

bimap :: (a -> b) -> (c -> d) -> Tagged a c -> Tagged b d #

first :: (a -> b) -> Tagged a c -> Tagged b c #

second :: (b -> c) -> Tagged a b -> Tagged a c #

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) #

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

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

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 #

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

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

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) #

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

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

Functor f => Bifunctor (Clown f :: Type -> Type -> Type) 
Instance details

Defined in Data.Bifunctor.Clown

Methods

bimap :: (a -> b) -> (c -> d) -> Clown f a c -> Clown f b d #

first :: (a -> b) -> Clown f a c -> Clown f b c #

second :: (b -> c) -> Clown f a b -> Clown f a c #

Bifunctor p => Bifunctor (Flip p) 
Instance details

Defined in Data.Bifunctor.Flip

Methods

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

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

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

Functor g => Bifunctor (Joker g :: Type -> Type -> Type) 
Instance details

Defined in Data.Bifunctor.Joker

Methods

bimap :: (a -> b) -> (c -> d) -> Joker g a c -> Joker g b d #

first :: (a -> b) -> Joker g a c -> Joker g b c #

second :: (b -> c) -> Joker g a b -> Joker g a c #

Bifunctor p => Bifunctor (WrappedBifunctor p) 
Instance details

Defined in Data.Bifunctor.Wrapped

Methods

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

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

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

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) #

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

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

(Bifunctor f, Bifunctor g) => Bifunctor (Product f g) 
Instance details

Defined in Data.Bifunctor.Product

Methods

bimap :: (a -> b) -> (c -> d) -> Product f g a c -> Product f g b d #

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

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

(Bifunctor p, Bifunctor q) => Bifunctor (Sum p q) 
Instance details

Defined in Data.Bifunctor.Sum

Methods

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

first :: (a -> b) -> Sum p q a c -> Sum p q b c #

second :: (b -> c) -> Sum p q a b -> Sum p q a c #

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) #

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

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

(Functor f, Bifunctor p) => Bifunctor (Tannen f p) 
Instance details

Defined in Data.Bifunctor.Tannen

Methods

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

first :: (a -> b) -> Tannen f p a c -> Tannen f p b c #

second :: (b -> c) -> Tannen f p a b -> Tannen f p a c #

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) #

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

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

(Bifunctor p, Functor f, Functor g) => Bifunctor (Biff p f g) 
Instance details

Defined in Data.Bifunctor.Biff

Methods

bimap :: (a -> b) -> (c -> d) -> Biff p f g a c -> Biff p f g b d #

first :: (a -> b) -> Biff p f g a c -> Biff p f g b c #

second :: (b -> c) -> Biff p f g a b -> Biff p f g a c #

first :: Bifunctor p => (a -> b) -> p a c -> p b c #

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 :: Bifunctor p => (b -> c) -> p a b -> p a c #

Map covariantly over the second argument.

secondbimap id

Examples

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

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

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

both :: Bifunctor bi => (a -> b) -> bi a a -> bi b b Source #

Map the same function over both sides of a Bifunctor (e.g. a tuple).

foldMap :: (Foldable t, Monoid m) => (a -> m) -> t a -> m #

Map each element of the structure into a monoid, and combine the results with (<>). This fold is right-associative and lazy in the accumulator. For strict left-associative folds consider foldMap' instead.

Examples

Expand

Basic usage:

>>> foldMap Sum [1, 3, 5]
Sum {getSum = 9}
>>> foldMap Product [1, 3, 5]
Product {getProduct = 15}
>>> foldMap (replicate 3) [1, 2, 3]
[1,1,1,2,2,2,3,3,3]

When a Monoid's (<>) is lazy in its second argument, foldMap can return a result even from an unbounded structure. For example, lazy accumulation enables Data.ByteString.Builder to efficiently serialise large data structures and produce the output incrementally:

>>> import qualified Data.ByteString.Lazy as L
>>> import qualified Data.ByteString.Builder as B
>>> let bld :: Int -> B.Builder; bld i = B.intDec i <> B.word8 0x20
>>> let lbs = B.toLazyByteString $ foldMap bld [0..]
>>> L.take 64 lbs
"0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24"

fold :: (Foldable t, Monoid m) => t m -> m #

Given a structure with elements whose type is a Monoid, combine them via the monoid's (<>) operator. This fold is right-associative and lazy in the accumulator. When you need a strict left-associative fold, use foldMap' instead, with id as the map.

Examples

Expand

Basic usage:

>>> fold [[1, 2, 3], [4, 5], [6], []]
[1,2,3,4,5,6]
>>> fold $ Node (Leaf (Sum 1)) (Sum 3) (Leaf (Sum 5))
Sum {getSum = 9}

Folds of unbounded structures do not terminate when the monoid's (<>) operator is strict:

>>> fold (repeat Nothing)
* Hangs forever *

Lazy corecursive folds of unbounded structures are fine:

>>> take 12 $ fold $ map (\i -> [i..i+2]) [0..]
[0,1,2,1,2,3,2,3,4,3,4,5]
>>> sum $ take 4000000 $ fold $ map (\i -> [i..i+2]) [0..]
2666668666666

foldl' :: Foldable t => (b -> a -> b) -> b -> t a -> b #

Left-associative fold of a structure but with strict application of the operator.

This ensures that each step of the fold is forced to Weak Head Normal Form before being applied, avoiding the collection of thunks that would otherwise occur. This is often what you want to strictly reduce a finite structure to a single strict result (e.g. sum).

For a general Foldable structure this should be semantically identical to,

foldl' f z = foldl' f z . toList

Since: base-4.6.0.0

fromMaybe :: a -> Maybe a -> a #

The fromMaybe function takes a default value and a Maybe value. If the Maybe is Nothing, it returns the default value; otherwise, it returns the value contained in the Maybe.

Examples

Expand

Basic usage:

>>> fromMaybe "" (Just "Hello, World!")
"Hello, World!"
>>> fromMaybe "" Nothing
""

Read an integer from a string using readMaybe. If we fail to parse an integer, we want to return 0 by default:

>>> import Text.Read ( readMaybe )
>>> fromMaybe 0 (readMaybe "5")
5
>>> fromMaybe 0 (readMaybe "")
0

mapMaybe :: (a -> Maybe b) -> [a] -> [b] #

The mapMaybe function is a version of map which can throw out elements. In particular, the functional argument returns something of type Maybe b. If this is Nothing, no element is added on to the result list. If it is Just b, then b is included in the result list.

Examples

Expand

Using mapMaybe f x is a shortcut for catMaybes $ map f x in most cases:

>>> import Text.Read ( readMaybe )
>>> let readMaybeInt = readMaybe :: String -> Maybe Int
>>> mapMaybe readMaybeInt ["1", "Foo", "3"]
[1,3]
>>> catMaybes $ map readMaybeInt ["1", "Foo", "3"]
[1,3]

If we map the Just constructor, the entire list should be returned:

>>> mapMaybe Just [1,2,3]
[1,2,3]

findMaybe :: Foldable t => (a -> Maybe b) -> t a -> Maybe b Source #

Find the first element for which pred returns `Just a`, and return the a.

Example: @ >>> :set -XTypeApplications >>> import qualified Text.Read

>>> findMaybe (Text.Read.readMaybe @Int) ["foo"]
Nothing
>>> findMaybe (Text.Read.readMaybe @Int) ["foo", "34.40", "34", "abc"]
Just 34

class (Functor t, Foldable t) => Traversable (t :: Type -> Type) #

Functors representing data structures that can be transformed to structures of the same shape by performing an Applicative (or, therefore, Monad) action on each element from left to right.

A more detailed description of what same shape means, the various methods, how traversals are constructed, and example advanced use-cases can be found in the Overview section of Data.Traversable.

For the class laws see the Laws section of Data.Traversable.

Minimal complete definition

traverse | sequenceA

Instances

Instances details
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) #

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

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

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

Traversable Complex

Since: base-4.9.0.0

Instance details

Defined in Data.Complex

Methods

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

sequenceA :: Applicative f => Complex (f a) -> f (Complex a) #

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

sequence :: Monad m => Complex (m a) -> m (Complex a) #

Traversable Identity

Since: base-4.9.0.0

Instance details

Defined in Data.Traversable

Methods

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

sequenceA :: Applicative f => Identity (f a) -> f (Identity a) #

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

sequence :: Monad m => Identity (m a) -> m (Identity a) #

Traversable First

Since: base-4.8.0.0

Instance details

Defined in Data.Traversable

Methods

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

sequenceA :: Applicative f => First (f a) -> f (First a) #

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

sequence :: Monad m => First (m a) -> m (First a) #

Traversable Last

Since: base-4.8.0.0

Instance details

Defined in Data.Traversable

Methods

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

sequenceA :: Applicative f => Last (f a) -> f (Last a) #

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

sequence :: Monad m => Last (m a) -> m (Last a) #

Traversable Down

Since: base-4.12.0.0

Instance details

Defined in Data.Traversable

Methods

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

sequenceA :: Applicative f => Down (f a) -> f (Down a) #

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

sequence :: Monad m => Down (m a) -> m (Down a) #

Traversable First

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Methods

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

sequenceA :: Applicative f => First (f a) -> f (First a) #

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

sequence :: Monad m => First (m a) -> m (First a) #

Traversable Last

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Methods

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

sequenceA :: Applicative f => Last (f a) -> f (Last a) #

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

sequence :: Monad m => Last (m a) -> m (Last a) #

Traversable Max

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Methods

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

sequenceA :: Applicative f => Max (f a) -> f (Max a) #

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

sequence :: Monad m => Max (m a) -> m (Max a) #

Traversable Min

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Methods

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

sequenceA :: Applicative f => Min (f a) -> f (Min a) #

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

sequence :: Monad m => Min (m a) -> m (Min a) #

Traversable Dual

Since: base-4.8.0.0

Instance details

Defined in Data.Traversable

Methods

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

sequenceA :: Applicative f => Dual (f a) -> f (Dual a) #

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

sequence :: Monad m => Dual (m a) -> m (Dual a) #

Traversable Product

Since: base-4.8.0.0

Instance details

Defined in Data.Traversable

Methods

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

sequenceA :: Applicative f => Product (f a) -> f (Product a) #

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

sequence :: Monad m => Product (m a) -> m (Product a) #

Traversable Sum

Since: base-4.8.0.0

Instance details

Defined in Data.Traversable

Methods

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

sequenceA :: Applicative f => Sum (f a) -> f (Sum a) #

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

sequence :: Monad m => Sum (m a) -> m (Sum a) #

Traversable Par1

Since: base-4.9.0.0

Instance details

Defined in Data.Traversable

Methods

traverse :: Applicative f => (a -> f b) -> Par1 a -> f (Par1 b) #

sequenceA :: Applicative f => Par1 (f a) -> f (Par1 a) #

mapM :: Monad m => (a -> m b) -> Par1 a -> m (Par1 b) #

sequence :: Monad m => Par1 (m a) -> m (Par1 a) #

Traversable SCC

Since: containers-0.5.9

Instance details

Defined in Data.Graph

Methods

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

sequenceA :: Applicative f => SCC (f a) -> f (SCC a) #

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

sequence :: Monad m => SCC (m a) -> m (SCC a) #

Traversable IntMap

Traverses in order of increasing key.

Instance details

Defined in Data.IntMap.Internal

Methods

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

sequenceA :: Applicative f => IntMap (f a) -> f (IntMap a) #

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

sequence :: Monad m => IntMap (m a) -> m (IntMap a) #

Traversable Digit 
Instance details

Defined in Data.Sequence.Internal

Methods

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

sequenceA :: Applicative f => Digit (f a) -> f (Digit a) #

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

sequence :: Monad m => Digit (m a) -> m (Digit a) #

Traversable Elem 
Instance details

Defined in Data.Sequence.Internal

Methods

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

sequenceA :: Applicative f => Elem (f a) -> f (Elem a) #

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

sequence :: Monad m => Elem (m a) -> m (Elem a) #

Traversable FingerTree 
Instance details

Defined in Data.Sequence.Internal

Methods

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

sequenceA :: Applicative f => FingerTree (f a) -> f (FingerTree a) #

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

sequence :: Monad m => FingerTree (m a) -> m (FingerTree a) #

Traversable Node 
Instance details

Defined in Data.Sequence.Internal

Methods

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

sequenceA :: Applicative f => Node (f a) -> f (Node a) #

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

sequence :: Monad m => Node (m a) -> m (Node a) #

Traversable Seq 
Instance details

Defined in Data.Sequence.Internal

Methods

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

sequenceA :: Applicative f => Seq (f a) -> f (Seq a) #

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

sequence :: Monad m => Seq (m a) -> m (Seq a) #

Traversable ViewL 
Instance details

Defined in Data.Sequence.Internal

Methods

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

sequenceA :: Applicative f => ViewL (f a) -> f (ViewL a) #

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

sequence :: Monad m => ViewL (m a) -> m (ViewL a) #

Traversable ViewR 
Instance details

Defined in Data.Sequence.Internal

Methods

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

sequenceA :: Applicative f => ViewR (f a) -> f (ViewR a) #

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

sequence :: Monad m => ViewR (m a) -> m (ViewR a) #

Traversable Tree 
Instance details

Defined in Data.Tree

Methods

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

sequenceA :: Applicative f => Tree (f a) -> f (Tree a) #

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

sequence :: Monad m => Tree (m a) -> m (Tree a) #

Traversable UniqueMap 
Instance details

Defined in GHC.Cmm.Dataflow.Collections

Methods

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

sequenceA :: Applicative f => UniqueMap (f a) -> f (UniqueMap a) #

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

sequence :: Monad m => UniqueMap (m a) -> m (UniqueMap a) #

Traversable LabelMap 
Instance details

Defined in GHC.Cmm.Dataflow.Label

Methods

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

sequenceA :: Applicative f => LabelMap (f a) -> f (LabelMap a) #

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

sequence :: Monad m => LabelMap (m a) -> m (LabelMap a) #

Traversable Bag 
Instance details

Defined in GHC.Data.Bag

Methods

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

sequenceA :: Applicative f => Bag (f a) -> f (Bag a) #

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

sequence :: Monad m => Bag (m a) -> m (Bag a) #

Traversable SizedSeq 
Instance details

Defined in GHC.Data.SizedSeq

Methods

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

sequenceA :: Applicative f => SizedSeq (f a) -> f (SizedSeq a) #

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

sequence :: Monad m => SizedSeq (m a) -> m (SizedSeq a) #

Traversable GenClosure 
Instance details

Defined in GHC.Exts.Heap.Closures

Methods

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

sequenceA :: Applicative f => GenClosure (f a) -> f (GenClosure a) #

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

sequence :: Monad m => GenClosure (m a) -> m (GenClosure a) #

Traversable NonEmpty

Since: base-4.9.0.0

Instance details

Defined in Data.Traversable

Methods

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

sequenceA :: Applicative f => NonEmpty (f a) -> f (NonEmpty a) #

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

sequence :: Monad m => NonEmpty (m a) -> m (NonEmpty a) #

Traversable Maybe

Since: base-2.1

Instance details

Defined in Data.Traversable

Methods

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

sequenceA :: Applicative f => Maybe (f a) -> f (Maybe a) #

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

sequence :: Monad m => Maybe (m a) -> m (Maybe a) #

Traversable Solo

Since: base-4.15

Instance details

Defined in Data.Traversable

Methods

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

sequenceA :: Applicative f => Solo (f a) -> f (Solo a) #

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

sequence :: Monad m => Solo (m a) -> m (Solo a) #

Traversable []

Since: base-2.1

Instance details

Defined in Data.Traversable

Methods

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

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

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

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

Traversable (Either a)

Since: base-4.7.0.0

Instance details

Defined in Data.Traversable

Methods

traverse :: Applicative f => (a0 -> f b) -> Either a a0 -> f (Either a b) #

sequenceA :: Applicative f => Either a (f a0) -> f (Either a a0) #

mapM :: Monad m => (a0 -> m b) -> Either a a0 -> m (Either a b) #

sequence :: Monad m => Either a (m a0) -> m (Either a a0) #

Traversable (Proxy :: Type -> Type)

Since: base-4.7.0.0

Instance details

Defined in Data.Traversable

Methods

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

sequenceA :: Applicative f => Proxy (f a) -> f (Proxy a) #

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

sequence :: Monad m => Proxy (m a) -> m (Proxy a) #

Traversable (Arg a)

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Methods

traverse :: Applicative f => (a0 -> f b) -> Arg a a0 -> f (Arg a b) #

sequenceA :: Applicative f => Arg a (f a0) -> f (Arg a a0) #

mapM :: Monad m => (a0 -> m b) -> Arg a a0 -> m (Arg a b) #

sequence :: Monad m => Arg a (m a0) -> m (Arg a a0) #

Ix i => Traversable (Array i)

Since: base-2.1

Instance details

Defined in Data.Traversable

Methods

traverse :: Applicative f => (a -> f b) -> Array i a -> f (Array i b) #

sequenceA :: Applicative f => Array i (f a) -> f (Array i a) #

mapM :: Monad m => (a -> m b) -> Array i a -> m (Array i b) #

sequence :: Monad m => Array i (m a) -> m (Array i a) #

Traversable (U1 :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in Data.Traversable

Methods

traverse :: Applicative f => (a -> f b) -> U1 a -> f (U1 b) #

sequenceA :: Applicative f => U1 (f a) -> f (U1 a) #

mapM :: Monad m => (a -> m b) -> U1 a -> m (U1 b) #

sequence :: Monad m => U1 (m a) -> m (U1 a) #

Traversable (UAddr :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in Data.Traversable

Methods

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

sequenceA :: Applicative f => UAddr (f a) -> f (UAddr a) #

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

sequence :: Monad m => UAddr (m a) -> m (UAddr a) #

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) #

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

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

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

Traversable (UDouble :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in Data.Traversable

Methods

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

sequenceA :: Applicative f => UDouble (f a) -> f (UDouble a) #

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

sequence :: Monad m => UDouble (m a) -> m (UDouble a) #

Traversable (UFloat :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in Data.Traversable

Methods

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

sequenceA :: Applicative f => UFloat (f a) -> f (UFloat a) #

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

sequence :: Monad m => UFloat (m a) -> m (UFloat a) #

Traversable (UInt :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in Data.Traversable

Methods

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

sequenceA :: Applicative f => UInt (f a) -> f (UInt a) #

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

sequence :: Monad m => UInt (m a) -> m (UInt a) #

Traversable (UWord :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in Data.Traversable

Methods

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

sequenceA :: Applicative f => UWord (f a) -> f (UWord a) #

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

sequence :: Monad m => UWord (m a) -> m (UWord a) #

Traversable (V1 :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in Data.Traversable

Methods

traverse :: Applicative f => (a -> f b) -> V1 a -> f (V1 b) #

sequenceA :: Applicative f => V1 (f a) -> f (V1 a) #

mapM :: Monad m => (a -> m b) -> V1 a -> m (V1 b) #

sequence :: Monad m => V1 (m a) -> m (V1 a) #

Traversable (Map k)

Traverses in order of increasing key.

Instance details

Defined in Data.Map.Internal

Methods

traverse :: Applicative f => (a -> f b) -> Map k a -> f (Map k b) #

sequenceA :: Applicative f => Map k (f a) -> f (Map k a) #

mapM :: Monad m => (a -> m b) -> Map k a -> m (Map k b) #

sequence :: Monad m => Map k (m a) -> m (Map k a) #

Traversable (These a) 
Instance details

Defined in Data.These

Methods

traverse :: Applicative f => (a0 -> f b) -> These a a0 -> f (These a b) #

sequenceA :: Applicative f => These a (f a0) -> f (These a a0) #

mapM :: Monad m => (a0 -> m b) -> These a a0 -> m (These a b) #

sequence :: Monad m => These a (m a0) -> m (These a a0) #

Traversable f => Traversable (Lift f) 
Instance details

Defined in Control.Applicative.Lift

Methods

traverse :: Applicative f0 => (a -> f0 b) -> Lift f a -> f0 (Lift f b) #

sequenceA :: Applicative f0 => Lift f (f0 a) -> f0 (Lift f a) #

mapM :: Monad m => (a -> m b) -> Lift f a -> m (Lift f b) #

sequence :: Monad m => Lift f (m a) -> m (Lift f a) #

Traversable (HashMap k) 
Instance details

Defined in Data.HashMap.Internal

Methods

traverse :: Applicative f => (a -> f b) -> HashMap k a -> f (HashMap k b) #

sequenceA :: Applicative f => HashMap k (f a) -> f (HashMap k a) #

mapM :: Monad m => (a -> m b) -> HashMap k a -> m (HashMap k b) #

sequence :: Monad m => HashMap k (m a) -> m (HashMap k a) #

Traversable (Validation e)

Traverse values inside Success with some effectful computation.

Examples

>>> parseInt = readMaybe :: String -> Maybe Int
>>> traverse parseInt (Success "42")
Just (Success 42)
>>> traverse parseInt (Success "int")
Nothing
>>> traverse parseInt (Failure ["42"])
Just (Failure ["42"])
Instance details

Defined in Validation

Methods

traverse :: Applicative f => (a -> f b) -> Validation e a -> f (Validation e b) #

sequenceA :: Applicative f => Validation e (f a) -> f (Validation e a) #

mapM :: Monad m => (a -> m b) -> Validation e a -> m (Validation e b) #

sequence :: Monad m => Validation e (m a) -> m (Validation e a) #

Traversable ((,) a)

Since: base-4.7.0.0

Instance details

Defined in Data.Traversable

Methods

traverse :: Applicative f => (a0 -> f b) -> (a, a0) -> f (a, b) #

sequenceA :: Applicative f => (a, f a0) -> f (a, a0) #

mapM :: Monad m => (a0 -> m b) -> (a, a0) -> m (a, b) #

sequence :: Monad m => (a, m a0) -> m (a, a0) #

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) #

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

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

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

Traversable f => Traversable (Ap f)

Since: base-4.12.0.0

Instance details

Defined in Data.Traversable

Methods

traverse :: Applicative f0 => (a -> f0 b) -> Ap f a -> f0 (Ap f b) #

sequenceA :: Applicative f0 => Ap f (f0 a) -> f0 (Ap f a) #

mapM :: Monad m => (a -> m b) -> Ap f a -> m (Ap f b) #

sequence :: Monad m => Ap f (m a) -> m (Ap f a) #

Traversable f => Traversable (Alt f)

Since: base-4.12.0.0

Instance details

Defined in Data.Traversable

Methods

traverse :: Applicative f0 => (a -> f0 b) -> Alt f a -> f0 (Alt f b) #

sequenceA :: Applicative f0 => Alt f (f0 a) -> f0 (Alt f a) #

mapM :: Monad m => (a -> m b) -> Alt f a -> m (Alt f b) #

sequence :: Monad m => Alt f (m a) -> m (Alt f a) #

Traversable f => Traversable (Rec1 f)

Since: base-4.9.0.0

Instance details

Defined in Data.Traversable

Methods

traverse :: Applicative f0 => (a -> f0 b) -> Rec1 f a -> f0 (Rec1 f b) #

sequenceA :: Applicative f0 => Rec1 f (f0 a) -> f0 (Rec1 f a) #

mapM :: Monad m => (a -> m b) -> Rec1 f a -> m (Rec1 f b) #

sequence :: Monad m => Rec1 f (m a) -> m (Rec1 f a) #

Bitraversable p => Traversable (Join p) 
Instance details

Defined in Data.Bifunctor.Join

Methods

traverse :: Applicative f => (a -> f b) -> Join p a -> f (Join p b) #

sequenceA :: Applicative f => Join p (f a) -> f (Join p a) #

mapM :: Monad m => (a -> m b) -> Join p a -> m (Join p b) #

sequence :: Monad m => Join p (m a) -> m (Join p a) #

Traversable (Tagged s) 
Instance details

Defined in Data.Tagged

Methods

traverse :: Applicative f => (a -> f b) -> Tagged s a -> f (Tagged s b) #

sequenceA :: Applicative f => Tagged s (f a) -> f (Tagged s a) #

mapM :: Monad m => (a -> m b) -> Tagged s a -> m (Tagged s b) #

sequence :: Monad m => Tagged s (m a) -> m (Tagged s a) #

Traversable f => Traversable (Backwards f)

Derived instance.

Instance details

Defined in Control.Applicative.Backwards

Methods

traverse :: Applicative f0 => (a -> f0 b) -> Backwards f a -> f0 (Backwards f b) #

sequenceA :: Applicative f0 => Backwards f (f0 a) -> f0 (Backwards f a) #

mapM :: Monad m => (a -> m b) -> Backwards f a -> m (Backwards f b) #

sequence :: Monad m => Backwards f (m a) -> m (Backwards f a) #

Traversable f => Traversable (ErrorT e f) 
Instance details

Defined in Control.Monad.Trans.Error

Methods

traverse :: Applicative f0 => (a -> f0 b) -> ErrorT e f a -> f0 (ErrorT e f b) #

sequenceA :: Applicative f0 => ErrorT e f (f0 a) -> f0 (ErrorT e f a) #

mapM :: Monad m => (a -> m b) -> ErrorT e f a -> m (ErrorT e f b) #

sequence :: Monad m => ErrorT e f (m a) -> m (ErrorT e f a) #

Traversable f => Traversable (ExceptT e f) 
Instance details

Defined in Control.Monad.Trans.Except

Methods

traverse :: Applicative f0 => (a -> f0 b) -> ExceptT e f a -> f0 (ExceptT e f b) #

sequenceA :: Applicative f0 => ExceptT e f (f0 a) -> f0 (ExceptT e f a) #

mapM :: Monad m => (a -> m b) -> ExceptT e f a -> m (ExceptT e f b) #

sequence :: Monad m => ExceptT e f (m a) -> m (ExceptT e f a) #

Traversable f => Traversable (IdentityT f) 
Instance details

Defined in Control.Monad.Trans.Identity

Methods

traverse :: Applicative f0 => (a -> f0 b) -> IdentityT f a -> f0 (IdentityT f b) #

sequenceA :: Applicative f0 => IdentityT f (f0 a) -> f0 (IdentityT f a) #

mapM :: Monad m => (a -> m b) -> IdentityT f a -> m (IdentityT f b) #

sequence :: Monad m => IdentityT f (m a) -> m (IdentityT f a) #

Traversable f => Traversable (Reverse f)

Traverse from right to left.

Instance details

Defined in Data.Functor.Reverse

Methods

traverse :: Applicative f0 => (a -> f0 b) -> Reverse f a -> f0 (Reverse f b) #

sequenceA :: Applicative f0 => Reverse f (f0 a) -> f0 (Reverse f a) #

mapM :: Monad m => (a -> m b) -> Reverse f a -> m (Reverse f b) #

sequence :: Monad m => Reverse f (m a) -> m (Reverse f a) #

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

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Product

Methods

traverse :: Applicative f0 => (a -> f0 b) -> Product f g a -> f0 (Product f g b) #

sequenceA :: Applicative f0 => Product f g (f0 a) -> f0 (Product f g a) #

mapM :: Monad m => (a -> m b) -> Product f g a -> m (Product f g b) #

sequence :: Monad m => Product f g (m a) -> m (Product f g a) #

(Traversable f, Traversable g) => Traversable (Sum f g)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Sum

Methods

traverse :: Applicative f0 => (a -> f0 b) -> Sum f g a -> f0 (Sum f g b) #

sequenceA :: Applicative f0 => Sum f g (f0 a) -> f0 (Sum f g a) #

mapM :: Monad m => (a -> m b) -> Sum f g a -> m (Sum f g b) #

sequence :: Monad m => Sum f g (m a) -> m (Sum f g a) #

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

Since: base-4.9.0.0

Instance details

Defined in Data.Traversable

Methods

traverse :: Applicative f0 => (a -> f0 b) -> (f :*: g) a -> f0 ((f :*: g) b) #

sequenceA :: Applicative f0 => (f :*: g) (f0 a) -> f0 ((f :*: g) a) #

mapM :: Monad m => (a -> m b) -> (f :*: g) a -> m ((f :*: g) b) #

sequence :: Monad m => (f :*: g) (m a) -> m ((f :*: g) a) #

(Traversable f, Traversable g) => Traversable (f :+: g)

Since: base-4.9.0.0

Instance details

Defined in Data.Traversable

Methods

traverse :: Applicative f0 => (a -> f0 b) -> (f :+: g) a -> f0 ((f :+: g) b) #

sequenceA :: Applicative f0 => (f :+: g) (f0 a) -> f0 ((f :+: g) a) #

mapM :: Monad m => (a -> m b) -> (f :+: g) a -> m ((f :+: g) b) #

sequence :: Monad m => (f :+: g) (m a) -> m ((f :+: g) a) #

Traversable (K1 i c :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in Data.Traversable

Methods

traverse :: Applicative f => (a -> f b) -> K1 i c a -> f (K1 i c b) #

sequenceA :: Applicative f => K1 i c (f a) -> f (K1 i c a) #

mapM :: Monad m => (a -> m b) -> K1 i c a -> m (K1 i c b) #

sequence :: Monad m => K1 i c (m a) -> m (K1 i c a) #

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

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Compose

Methods

traverse :: Applicative f0 => (a -> f0 b) -> Compose f g a -> f0 (Compose f g b) #

sequenceA :: Applicative f0 => Compose f g (f0 a) -> f0 (Compose f g a) #

mapM :: Monad m => (a -> m b) -> Compose f g a -> m (Compose f g b) #

sequence :: Monad m => Compose f g (m a) -> m (Compose f g a) #

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

Since: base-4.9.0.0

Instance details

Defined in Data.Traversable

Methods

traverse :: Applicative f0 => (a -> f0 b) -> (f :.: g) a -> f0 ((f :.: g) b) #

sequenceA :: Applicative f0 => (f :.: g) (f0 a) -> f0 ((f :.: g) a) #

mapM :: Monad m => (a -> m b) -> (f :.: g) a -> m ((f :.: g) b) #

sequence :: Monad m => (f :.: g) (m a) -> m ((f :.: g) a) #

Traversable f => Traversable (M1 i c f)

Since: base-4.9.0.0

Instance details

Defined in Data.Traversable

Methods

traverse :: Applicative f0 => (a -> f0 b) -> M1 i c f a -> f0 (M1 i c f b) #

sequenceA :: Applicative f0 => M1 i c f (f0 a) -> f0 (M1 i c f a) #

mapM :: Monad m => (a -> m b) -> M1 i c f a -> m (M1 i c f b) #

sequence :: Monad m => M1 i c f (m a) -> m (M1 i c f a) #

Traversable (Clown f a :: Type -> Type) 
Instance details

Defined in Data.Bifunctor.Clown

Methods

traverse :: Applicative f0 => (a0 -> f0 b) -> Clown f a a0 -> f0 (Clown f a b) #

sequenceA :: Applicative f0 => Clown f a (f0 a0) -> f0 (Clown f a a0) #

mapM :: Monad m => (a0 -> m b) -> Clown f a a0 -> m (Clown f a b) #

sequence :: Monad m => Clown f a (m a0) -> m (Clown f a a0) #

Bitraversable p => Traversable (Flip p a) 
Instance details

Defined in Data.Bifunctor.Flip

Methods

traverse :: Applicative f => (a0 -> f b) -> Flip p a a0 -> f (Flip p a b) #

sequenceA :: Applicative f => Flip p a (f a0) -> f (Flip p a a0) #

mapM :: Monad m => (a0 -> m b) -> Flip p a a0 -> m (Flip p a b) #

sequence :: Monad m => Flip p a (m a0) -> m (Flip p a a0) #

Traversable g => Traversable (Joker g a) 
Instance details

Defined in Data.Bifunctor.Joker

Methods

traverse :: Applicative f => (a0 -> f b) -> Joker g a a0 -> f (Joker g a b) #

sequenceA :: Applicative f => Joker g a (f a0) -> f (Joker g a a0) #

mapM :: Monad m => (a0 -> m b) -> Joker g a a0 -> m (Joker g a b) #

sequence :: Monad m => Joker g a (m a0) -> m (Joker g a a0) #

Bitraversable p => Traversable (WrappedBifunctor p a) 
Instance details

Defined in Data.Bifunctor.Wrapped

Methods

traverse :: Applicative f => (a0 -> f b) -> WrappedBifunctor p a a0 -> f (WrappedBifunctor p a b) #

sequenceA :: Applicative f => WrappedBifunctor p a (f a0) -> f (WrappedBifunctor p a a0) #

mapM :: Monad m => (a0 -> m b) -> WrappedBifunctor p a a0 -> m (WrappedBifunctor p a b) #

sequence :: Monad m => WrappedBifunctor p a (m a0) -> m (WrappedBifunctor p a a0) #

(Traversable (f a), Traversable (g a)) => Traversable (Product f g a) 
Instance details

Defined in Data.Bifunctor.Product

Methods

traverse :: Applicative f0 => (a0 -> f0 b) -> Product f g a a0 -> f0 (Product f g a b) #

sequenceA :: Applicative f0 => Product f g a (f0 a0) -> f0 (Product f g a a0) #

mapM :: Monad m => (a0 -> m b) -> Product f g a a0 -> m (Product f g a b) #

sequence :: Monad m => Product f g a (m a0) -> m (Product f g a a0) #

(Traversable (f a), Traversable (g a)) => Traversable (Sum f g a) 
Instance details

Defined in Data.Bifunctor.Sum

Methods

traverse :: Applicative f0 => (a0 -> f0 b) -> Sum f g a a0 -> f0 (Sum f g a b) #

sequenceA :: Applicative f0 => Sum f g a (f0 a0) -> f0 (Sum f g a a0) #

mapM :: Monad m => (a0 -> m b) -> Sum f g a a0 -> m (Sum f g a b) #

sequence :: Monad m => Sum f g a (m a0) -> m (Sum f g a a0) #

(Traversable f, Bitraversable p) => Traversable (Tannen f p a) 
Instance details

Defined in Data.Bifunctor.Tannen

Methods

traverse :: Applicative f0 => (a0 -> f0 b) -> Tannen f p a a0 -> f0 (Tannen f p a b) #

sequenceA :: Applicative f0 => Tannen f p a (f0 a0) -> f0 (Tannen f p a a0) #

mapM :: Monad m => (a0 -> m b) -> Tannen f p a a0 -> m (Tannen f p a b) #

sequence :: Monad m => Tannen f p a (m a0) -> m (Tannen f p a a0) #

(Bitraversable p, Traversable g) => Traversable (Biff p f g a) 
Instance details

Defined in Data.Bifunctor.Biff

Methods

traverse :: Applicative f0 => (a0 -> f0 b) -> Biff p f g a a0 -> f0 (Biff p f g a b) #

sequenceA :: Applicative f0 => Biff p f g a (f0 a0) -> f0 (Biff p f g a a0) #

mapM :: Monad m => (a0 -> m b) -> Biff p f g a a0 -> m (Biff p f g a b) #

sequence :: Monad m => Biff p f g a (m a0) -> m (Biff p f g a a0) #

for :: (Traversable t, Applicative f) => t a -> (a -> f b) -> f (t b) #

for is traverse with its arguments flipped. For a version that ignores the results see for_.

for_ :: (Foldable t, Applicative f) => t a -> (a -> f b) -> f () #

for_ is traverse_ with its arguments flipped. For a version that doesn't ignore the results see for. This is forM_ generalised to Applicative actions.

for_ is just like forM_, but generalised to Applicative actions.

Examples

Expand

Basic usage:

>>> for_ [1..4] print
1
2
3
4

traverse :: (Traversable t, Applicative f) => (a -> f b) -> t a -> f (t b) #

Map each element of a structure to an action, evaluate these actions from left to right, and collect the results. For a version that ignores the results see traverse_.

Examples

Expand

Basic usage:

In the first two examples we show each evaluated action mapping to the output structure.

>>> traverse Just [1,2,3,4]
Just [1,2,3,4]
>>> traverse id [Right 1, Right 2, Right 3, Right 4]
Right [1,2,3,4]

In the next examples, we show that Nothing and Left values short circuit the created structure.

>>> traverse (const Nothing) [1,2,3,4]
Nothing
>>> traverse (\x -> if odd x then Just x else Nothing)  [1,2,3,4]
Nothing
>>> traverse id [Right 1, Right 2, Right 3, Right 4, Left 0]
Left 0

traverse_ :: (Foldable t, Applicative f) => (a -> f b) -> t a -> f () #

Map each element of a structure to an Applicative action, evaluate these actions from left to right, and ignore the results. For a version that doesn't ignore the results see traverse.

traverse_ is just like mapM_, but generalised to Applicative actions.

Examples

Expand

Basic usage:

>>> traverse_ print ["Hello", "world", "!"]
"Hello"
"world"
"!"

traverseFold :: (Applicative ap, Traversable t, Monoid m) => (a -> ap m) -> t a -> ap m Source #

Run some function producing applicative over a traversable data structure, then collect the results in a Monoid.

Very helpful with side-effecting functions returning (Validation err a):

let
  f :: Text -> IO (Validation (NonEmpty Error) Text)
  f t = pure $ if t == "foo" then Success t else Failure (singleton ("not foo: " <> t))

in traverseFold f [ "foo", "bar", "baz" ]
  == Failure ("not foo bar" :| ["not foo baz"])

… since (Semigroup err => Validation err a) is a Semigroup/Monoid itself.

traverseFold1 :: (Applicative ap, Traversable1 t, Semigroup s) => (a -> ap s) -> t a -> ap s Source #

Same as traverseFold, but with a Semigroup and Traversable1 restriction.

traverseFoldDefault :: (Applicative ap, Traversable t, Semigroup m) => m -> (a -> ap m) -> t a -> ap m Source #

Like traverseFold, but fold over a semigroup instead of a Monoid, by providing a starting element.

class MonadTrans (t :: (Type -> Type) -> Type -> Type) #

The class of monad transformers. Instances should satisfy the following laws, which state that lift is a monad transformation:

Minimal complete definition

lift

Instances

Instances details
MonadTrans (ErrorT e) 
Instance details

Defined in Control.Monad.Trans.Error

Methods

lift :: Monad m => m a -> ErrorT e m a #

MonadTrans (ExceptT e) 
Instance details

Defined in Control.Monad.Trans.Except

Methods

lift :: Monad m => m a -> ExceptT e m a #

MonadTrans (IdentityT :: (Type -> Type) -> Type -> Type) 
Instance details

Defined in Control.Monad.Trans.Identity

Methods

lift :: Monad m => m a -> IdentityT m a #

lift :: (MonadTrans t, Monad m) => m a -> t m a #

Lift a computation from the argument monad to the constructed monad.

Data types

class a ~R# b => Coercible (a :: k) (b :: k) #

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-4.7.0.0

coerce :: forall {k :: RuntimeRep} (a :: TYPE k) (b :: TYPE k). Coercible a b => a -> b #

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 runtime-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.

data Proxy (t :: k) #

Proxy is a type that holds no data, but has a phantom parameter of arbitrary type (or even kind). Its use is to provide type information, even though there is no value available of that type (or it may be too costly to create one).

Historically, Proxy :: Proxy a is a safer alternative to the undefined :: a idiom.

>>> Proxy :: Proxy (Void, Int -> Int)
Proxy

Proxy can even hold types of higher kinds,

>>> Proxy :: Proxy Either
Proxy
>>> Proxy :: Proxy Functor
Proxy
>>> Proxy :: Proxy complicatedStructure
Proxy

Constructors

Proxy 

Instances

Instances details
Generic1 (Proxy :: k -> Type) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep1 Proxy :: k -> Type #

Methods

from1 :: forall (a :: k0). Proxy a -> Rep1 Proxy a #

to1 :: forall (a :: k0). Rep1 Proxy a -> Proxy a #

Foldable (Proxy :: TYPE LiftedRep -> Type)

Since: base-4.7.0.0

Instance details

Defined in Data.Foldable

Methods

fold :: Monoid m => Proxy m -> m #

foldMap :: Monoid m => (a -> m) -> Proxy a -> m #

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

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

foldr' :: (a -> b -> b) -> b -> Proxy a -> b #

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

foldl' :: (b -> a -> b) -> b -> Proxy a -> b #

foldr1 :: (a -> a -> a) -> Proxy a -> a #

foldl1 :: (a -> a -> a) -> Proxy a -> a #

toList :: Proxy a -> [a] #

null :: Proxy a -> Bool #

length :: Proxy a -> Int #

elem :: Eq a => a -> Proxy a -> Bool #

maximum :: Ord a => Proxy a -> a #

minimum :: Ord a => Proxy a -> a #

sum :: Num a => Proxy a -> a #

product :: Num a => Proxy a -> a #

Eq1 (Proxy :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

liftEq :: (a -> b -> Bool) -> Proxy a -> Proxy b -> Bool #

Ord1 (Proxy :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

liftCompare :: (a -> b -> Ordering) -> Proxy a -> Proxy b -> Ordering #

Read1 (Proxy :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

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

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

liftReadPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec (Proxy a) #

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

Show1 (Proxy :: TYPE LiftedRep -> Type)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

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

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

Contravariant (Proxy :: Type -> Type) 
Instance details

Defined in Data.Functor.Contravariant

Methods

contramap :: (a' -> a) -> Proxy a -> Proxy a' #

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

Traversable (Proxy :: Type -> Type)

Since: base-4.7.0.0

Instance details

Defined in Data.Traversable

Methods

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

sequenceA :: Applicative f => Proxy (f a) -> f (Proxy a) #

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

sequence :: Monad m => Proxy (m a) -> m (Proxy a) #

Alternative (Proxy :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in Data.Proxy

Methods

empty :: Proxy a #

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

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

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

Applicative (Proxy :: Type -> Type)

Since: base-4.7.0.0

Instance details

Defined in Data.Proxy

Methods

pure :: a -> Proxy a #

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

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

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

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

Functor (Proxy :: Type -> Type)

Since: base-4.7.0.0

Instance details

Defined in Data.Proxy

Methods

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

(<$) :: a -> Proxy b -> Proxy a #

Monad (Proxy :: Type -> Type)

Since: base-4.7.0.0

Instance details

Defined in Data.Proxy

Methods

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

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

return :: a -> Proxy a #

MonadPlus (Proxy :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in Data.Proxy

Methods

mzero :: Proxy a #

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

Hashable1 (Proxy :: Type -> Type) 
Instance details

Defined in Data.Hashable.Class

Methods

liftHashWithSalt :: (Int -> a -> Int) -> Int -> Proxy a -> Int #

Alt (Proxy :: Type -> Type) 
Instance details

Defined in Data.Functor.Alt

Methods

(<!>) :: Proxy a -> Proxy a -> Proxy a #

some :: Applicative Proxy => Proxy a -> Proxy [a] #

many :: Applicative Proxy => Proxy a -> Proxy [a] #

Apply (Proxy :: Type -> Type) 
Instance details

Defined in Data.Functor.Bind.Class

Methods

(<.>) :: Proxy (a -> b) -> Proxy a -> Proxy b #

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

(<.) :: Proxy a -> Proxy b -> Proxy a #

liftF2 :: (a -> b -> c) -> Proxy a -> Proxy b -> Proxy c #

Bind (Proxy :: Type -> Type) 
Instance details

Defined in Data.Functor.Bind.Class

Methods

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

join :: Proxy (Proxy a) -> Proxy a #

Extend (Proxy :: Type -> Type) 
Instance details

Defined in Data.Functor.Extend

Methods

duplicated :: Proxy a -> Proxy (Proxy a) #

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

Data t => Data (Proxy t)

Since: base-4.7.0.0

Instance details

Defined in Data.Data

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Proxy t -> c (Proxy t) #

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Proxy t) #

toConstr :: Proxy t -> Constr #

dataTypeOf :: Proxy t -> DataType #

dataCast1 :: Typeable t0 => (forall d. Data d => c (t0 d)) -> Maybe (c (Proxy t)) #

dataCast2 :: Typeable t0 => (forall d e. (Data d, Data e) => c (t0 d e)) -> Maybe (c (Proxy t)) #

gmapT :: (forall b. Data b => b -> b) -> Proxy t -> Proxy t #

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Proxy t -> r #

gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Proxy t -> r #

gmapQ :: (forall d. Data d => d -> u) -> Proxy t -> [u] #

gmapQi :: Int -> (forall d. Data d => d -> u) -> Proxy t -> u #

gmapM :: Monad m => (forall d. Data d => d -> m d) -> Proxy t -> m (Proxy t) #

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Proxy t -> m (Proxy t) #

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Proxy t -> m (Proxy t) #

Monoid (Proxy s)

Since: base-4.7.0.0

Instance details

Defined in Data.Proxy

Methods

mempty :: Proxy s #

mappend :: Proxy s -> Proxy s -> Proxy s #

mconcat :: [Proxy s] -> Proxy s #

Semigroup (Proxy s)

Since: base-4.9.0.0

Instance details

Defined in Data.Proxy

Methods

(<>) :: Proxy s -> Proxy s -> Proxy s #

sconcat :: NonEmpty (Proxy s) -> Proxy s #

stimes :: Integral b => b -> Proxy s -> Proxy s #

Bounded (Proxy t)

Since: base-4.7.0.0

Instance details

Defined in Data.Proxy

Methods

minBound :: Proxy t #

maxBound :: Proxy t #

Enum (Proxy s)

Since: base-4.7.0.0

Instance details

Defined in Data.Proxy

Methods

succ :: Proxy s -> Proxy s #

pred :: Proxy s -> Proxy s #

toEnum :: Int -> Proxy s #

fromEnum :: Proxy s -> Int #

enumFrom :: Proxy s -> [Proxy s] #

enumFromThen :: Proxy s -> Proxy s -> [Proxy s] #

enumFromTo :: Proxy s -> Proxy s -> [Proxy s] #

enumFromThenTo :: Proxy s -> Proxy s -> Proxy s -> [Proxy s] #

Generic (Proxy t) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (Proxy t) :: Type -> Type #

Methods

from :: Proxy t -> Rep (Proxy t) x #

to :: Rep (Proxy t) x -> Proxy t #

Ix (Proxy s)

Since: base-4.7.0.0

Instance details

Defined in Data.Proxy

Methods

range :: (Proxy s, Proxy s) -> [Proxy s] #

index :: (Proxy s, Proxy s) -> Proxy s -> Int #

unsafeIndex :: (Proxy s, Proxy s) -> Proxy s -> Int #

inRange :: (Proxy s, Proxy s) -> Proxy s -> Bool #

rangeSize :: (Proxy s, Proxy s) -> Int #

unsafeRangeSize :: (Proxy s, Proxy s) -> Int #

Read (Proxy t)

Since: base-4.7.0.0

Instance details

Defined in Data.Proxy

Show (Proxy s)

Since: base-4.7.0.0

Instance details

Defined in Data.Proxy

Methods

showsPrec :: Int -> Proxy s -> ShowS #

show :: Proxy s -> String #

showList :: [Proxy s] -> ShowS #

Eq (Proxy s)

Since: base-4.7.0.0

Instance details

Defined in Data.Proxy

Methods

(==) :: Proxy s -> Proxy s -> Bool #

(/=) :: Proxy s -> Proxy s -> Bool #

Ord (Proxy s)

Since: base-4.7.0.0

Instance details

Defined in Data.Proxy

Methods

compare :: Proxy s -> Proxy s -> Ordering #

(<) :: Proxy s -> Proxy s -> Bool #

(<=) :: Proxy s -> Proxy s -> Bool #

(>) :: Proxy s -> Proxy s -> Bool #

(>=) :: Proxy s -> Proxy s -> Bool #

max :: Proxy s -> Proxy s -> Proxy s #

min :: Proxy s -> Proxy s -> Proxy s #

Hashable (Proxy a) 
Instance details

Defined in Data.Hashable.Class

Methods

hashWithSalt :: Int -> Proxy a -> Int #

hash :: Proxy a -> Int #

type Rep1 (Proxy :: k -> Type)

Since: base-4.6.0.0

Instance details

Defined in GHC.Generics

type Rep1 (Proxy :: k -> Type) = D1 ('MetaData "Proxy" "Data.Proxy" "base" 'False) (C1 ('MetaCons "Proxy" 'PrefixI 'False) (U1 :: k -> Type))
type Rep (Proxy t)

Since: base-4.6.0.0

Instance details

Defined in GHC.Generics

type Rep (Proxy t) = D1 ('MetaData "Proxy" "Data.Proxy" "base" 'False) (C1 ('MetaCons "Proxy" 'PrefixI 'False) (U1 :: Type -> Type))

data Map k a #

A Map from keys k to values a.

The Semigroup operation for Map is union, which prefers values from the left operand. If m1 maps a key k to a value a1, and m2 maps the same key to a different value a2, then their union m1 <> m2 maps k to a1.

Instances

Instances details
Bifoldable Map

Since: containers-0.6.3.1

Instance details

Defined in Data.Map.Internal

Methods

bifold :: Monoid m => Map m m -> m #

bifoldMap :: Monoid m => (a -> m) -> (b -> m) -> Map a b -> m #

bifoldr :: (a -> c -> c) -> (b -> c -> c) -> c -> Map a b -> c #

bifoldl :: (c -> a -> c) -> (c -> b -> c) -> c -> Map a b -> c #

Eq2 Map

Since: containers-0.5.9

Instance details

Defined in Data.Map.Internal

Methods

liftEq2 :: (a -> b -> Bool) -> (c -> d -> Bool) -> Map a c -> Map b d -> Bool #

Ord2 Map

Since: containers-0.5.9

Instance details

Defined in Data.Map.Internal

Methods

liftCompare2 :: (a -> b -> Ordering) -> (c -> d -> Ordering) -> Map a c -> Map b d -> Ordering #

Show2 Map

Since: containers-0.5.9

Instance details

Defined in Data.Map.Internal

Methods

liftShowsPrec2 :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> (Int -> b -> ShowS) -> ([b] -> ShowS) -> Int -> Map a b -> ShowS #

liftShowList2 :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> (Int -> b -> ShowS) -> ([b] -> ShowS) -> [Map a b] -> ShowS #

Hashable2 Map

Since: hashable-1.3.4.0

Instance details

Defined in Data.Hashable.Class

Methods

liftHashWithSalt2 :: (Int -> a -> Int) -> (Int -> b -> Int) -> Int -> Map a b -> Int #

(OutputableP env key, OutputableP env elt) => OutputableP env (Map key elt) 
Instance details

Defined in GHC.Utils.Outputable

Methods

pdoc :: env -> Map key elt -> SDoc #

Foldable (Map k)

Folds in order of increasing key.

Instance details

Defined in Data.Map.Internal

Methods

fold :: Monoid m => Map k m -> m #

foldMap :: Monoid m => (a -> m) -> Map k a -> m #

foldMap' :: Monoid m => (a -> m) -> Map k a -> m #

foldr :: (a -> b -> b) -> b -> Map k a -> b #

foldr' :: (a -> b -> b) -> b -> Map k a -> b #

foldl :: (b -> a -> b) -> b -> Map k a -> b #

foldl' :: (b -> a -> b) -> b -> Map k a -> b #

foldr1 :: (a -> a -> a) -> Map k a -> a #

foldl1 :: (a -> a -> a) -> Map k a -> a #

toList :: Map k a -> [a] #

null :: Map k a -> Bool #

length :: Map k a -> Int #

elem :: Eq a => a -> Map k a -> Bool #

maximum :: Ord a => Map k a -> a #

minimum :: Ord a => Map k a -> a #

sum :: Num a => Map k a -> a #

product :: Num a => Map k a -> a #

Eq k => Eq1 (Map k)

Since: containers-0.5.9

Instance details

Defined in Data.Map.Internal

Methods

liftEq :: (a -> b -> Bool) -> Map k a -> Map k b -> Bool #

Ord k => Ord1 (Map k)

Since: containers-0.5.9

Instance details

Defined in Data.Map.Internal

Methods

liftCompare :: (a -> b -> Ordering) -> Map k a -> Map k b -> Ordering #

(Ord k, Read k) => Read1 (Map k)

Since: containers-0.5.9

Instance details

Defined in Data.Map.Internal

Methods

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

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

liftReadPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec (Map k a) #

liftReadListPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec [Map k a] #

Show k => Show1 (Map k)

Since: containers-0.5.9

Instance details

Defined in Data.Map.Internal

Methods

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

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

Traversable (Map k)

Traverses in order of increasing key.

Instance details

Defined in Data.Map.Internal

Methods

traverse :: Applicative f => (a -> f b) -> Map k a -> f (Map k b) #

sequenceA :: Applicative f => Map k (f a) -> f (Map k a) #

mapM :: Monad m => (a -> m b) -> Map k a -> m (Map k b) #

sequence :: Monad m => Map k (m a) -> m (Map k a) #

Functor (Map k) 
Instance details

Defined in Data.Map.Internal

Methods

fmap :: (a -> b) -> Map k a -> Map k b #

(<$) :: a -> Map k b -> Map k a #

Ord k => TrieMap (Map k) 
Instance details

Defined in GHC.Data.TrieMap

Associated Types

type Key (Map k) #

Methods

emptyTM :: Map k a #

lookupTM :: Key (Map k) -> Map k b -> Maybe b #

alterTM :: Key (Map k) -> XT b -> Map k b -> Map k b #

mapTM :: (a -> b) -> Map k a -> Map k b #

filterTM :: (a -> Bool) -> Map k a -> Map k a #

foldTM :: (a -> b -> b) -> Map k a -> b -> b #

Hashable k => Hashable1 (Map k)

Since: hashable-1.3.4.0

Instance details

Defined in Data.Hashable.Class

Methods

liftHashWithSalt :: (Int -> a -> Int) -> Int -> Map k a -> Int #

Ord k => Alt (Map k) 
Instance details

Defined in Data.Functor.Alt

Methods

(<!>) :: Map k a -> Map k a -> Map k a #

some :: Applicative (Map k) => Map k a -> Map k [a] #

many :: Applicative (Map k) => Map k a -> Map k [a] #

Ord k => Apply (Map k)

A 'Map k' is not Applicative, but it is an instance of Apply

Instance details

Defined in Data.Functor.Bind.Class

Methods

(<.>) :: Map k (a -> b) -> Map k a -> Map k b #

(.>) :: Map k a -> Map k b -> Map k b #

(<.) :: Map k a -> Map k b -> Map k a #

liftF2 :: (a -> b -> c) -> Map k a -> Map k b -> Map k c #

Ord k => Bind (Map k)

A 'Map k' is not a Monad, but it is an instance of Bind

Instance details

Defined in Data.Functor.Bind.Class

Methods

(>>-) :: Map k a -> (a -> Map k b) -> Map k b #

join :: Map k (Map k a) -> Map k a #

(Data k, Data a, Ord k) => Data (Map k a) 
Instance details

Defined in Data.Map.Internal

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Map k a -> c (Map k a) #

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Map k a) #

toConstr :: Map k a -> Constr #

dataTypeOf :: Map k a -> DataType #

dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Map k a)) #

dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Map k a)) #

gmapT :: (forall b. Data b => b -> b) -> Map k a -> Map k a #

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Map k a -> r #

gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Map k a -> r #

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

gmapQi :: Int -> (forall d. Data d => d -> u) -> Map k a -> u #

gmapM :: Monad m => (forall d. Data d => d -> m d) -> Map k a -> m (Map k a) #

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Map k a -> m (Map k a) #

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Map k a -> m (Map k a) #

Ord k => Monoid (Map k v) 
Instance details

Defined in Data.Map.Internal

Methods

mempty :: Map k v #

mappend :: Map k v -> Map k v -> Map k v #

mconcat :: [Map k v] -> Map k v #

Ord k => Semigroup (Map k v) 
Instance details

Defined in Data.Map.Internal

Methods

(<>) :: Map k v -> Map k v -> Map k v #

sconcat :: NonEmpty (Map k v) -> Map k v #

stimes :: Integral b => b -> Map k v -> Map k v #

Ord k => IsList (Map k v)

Since: containers-0.5.6.2

Instance details

Defined in Data.Map.Internal

Associated Types

type Item (Map k v) #

Methods

fromList :: [Item (Map k v)] -> Map k v #

fromListN :: Int -> [Item (Map k v)] -> Map k v #

toList :: Map k v -> [Item (Map k v)] #

(Ord k, Read k, Read e) => Read (Map k e) 
Instance details

Defined in Data.Map.Internal

Methods

readsPrec :: Int -> ReadS (Map k e) #

readList :: ReadS [Map k e] #

readPrec :: ReadPrec (Map k e) #

readListPrec :: ReadPrec [Map k e] #

(Show k, Show a) => Show (Map k a) 
Instance details

Defined in Data.Map.Internal

Methods

showsPrec :: Int -> Map k a -> ShowS #

show :: Map k a -> String #

showList :: [Map k a] -> ShowS #

(NFData k, NFData a) => NFData (Map k a) 
Instance details

Defined in Data.Map.Internal

Methods

rnf :: Map k a -> () #

(Outputable key, Outputable elt) => Outputable (Map key elt) 
Instance details

Defined in GHC.Utils.Outputable

Methods

ppr :: Map key elt -> SDoc #

(Eq k, Eq a) => Eq (Map k a) 
Instance details

Defined in Data.Map.Internal

Methods

(==) :: Map k a -> Map k a -> Bool #

(/=) :: Map k a -> Map k a -> Bool #

(Ord k, Ord v) => Ord (Map k v) 
Instance details

Defined in Data.Map.Internal

Methods

compare :: Map k v -> Map k v -> Ordering #

(<) :: Map k v -> Map k v -> Bool #

(<=) :: Map k v -> Map k v -> Bool #

(>) :: Map k v -> Map k v -> Bool #

(>=) :: Map k v -> Map k v -> Bool #

max :: Map k v -> Map k v -> Map k v #

min :: Map k v -> Map k v -> Map k v #

(Hashable k, Hashable v) => Hashable (Map k v)

Since: hashable-1.3.4.0

Instance details

Defined in Data.Hashable.Class

Methods

hashWithSalt :: Int -> Map k v -> Int #

hash :: Map k v -> Int #

type Key (Map k) 
Instance details

Defined in GHC.Data.TrieMap

type Key (Map k) = k
type Item (Map k v) 
Instance details

Defined in Data.Map.Internal

type Item (Map k v) = (k, v)

annotate :: err -> Maybe a -> Either err a Source #

Annotate a Maybe with an error message and turn it into an Either.

data Validation e a #

Validation is a polymorphic sum type for storing either all validation failures or validation success. Unlike Either, which returns only the first error, Validation accumulates all errors using the Semigroup typeclass.

Usually type variables in Validation e a are used as follows:

  • e: is a list or set of failure messages or values of some error data type.
  • a: is some domain type denoting successful validation result.

Some typical use-cases:

  • Validation [String] User
    • Either list of String error messages or a validated value of a custom User type.
  • Validation (NonEmpty UserValidationError) User
    • Similar to previous example, but list of failures guaranteed to be non-empty in case of validation failure, and it stores values of some custom error type.

Constructors

Failure e

Validation failure. The e type is supposed to implement the Semigroup instance.

Success a

Successful validation result of type a.

Instances

Instances details
Bifoldable Validation

Similar to Foldable but allows folding both Failure and Success to the same monoidal value according to given functions.

Examples

>>> one x = [x]
>>> bifoldMap id (one . show) (Success 15)
["15"]
>>> bifoldMap id (one . show) (Failure ["Wrong", "Fail"])
["Wrong","Fail"]
Instance details

Defined in Validation

Methods

bifold :: Monoid m => Validation m m -> m #

bifoldMap :: Monoid m => (a -> m) -> (b -> m) -> Validation a b -> m #

bifoldr :: (a -> c -> c) -> (b -> c -> c) -> c -> Validation a b -> c #

bifoldl :: (c -> a -> c) -> (c -> b -> c) -> c -> Validation a b -> c #

Bifunctor Validation

Similar to Functor but allows mapping of values inside both Failure and Success.

Examples

>>> bimap length show (Success 50)
Success "50"
>>> bimap length show (Failure ["15", "9"])
Failure 2
Instance details

Defined in Validation

Methods

bimap :: (a -> b) -> (c -> d) -> Validation a c -> Validation b d #

first :: (a -> b) -> Validation a c -> Validation b c #

second :: (b -> c) -> Validation a b -> Validation a c #

Bitraversable Validation

Similar to Traversable but traverses both Failure and Success with given effectful computations.

Examples

>>> parseInt = readMaybe :: String -> Maybe Int
>>> bitraverse listToMaybe parseInt (Success "42")
Just (Success 42)
>>> bitraverse listToMaybe parseInt (Success "int")
Nothing
>>> bitraverse listToMaybe parseInt (Failure [15])
Just (Failure 15)
>>> bitraverse listToMaybe parseInt (Failure [])
Nothing
Instance details

Defined in Validation

Methods

bitraverse :: Applicative f => (a -> f c) -> (b -> f d) -> Validation a b -> f (Validation c d) #

NFData2 Validation 
Instance details

Defined in Validation

Methods

liftRnf2 :: (a -> ()) -> (b -> ()) -> Validation a b -> () #

Generic1 (Validation e :: Type -> Type) 
Instance details

Defined in Validation

Associated Types

type Rep1 (Validation e) :: k -> Type #

Methods

from1 :: forall (a :: k). Validation e a -> Rep1 (Validation e) a #

to1 :: forall (a :: k). Rep1 (Validation e) a -> Validation e a #

Foldable (Validation e)

Foldable for Validation allows folding values inside Success.

Examples

>>> fold (Success [16])
[16]
>>> fold (Failure "WRONG!" :: Validation String [Int])
[]
Instance details

Defined in Validation

Methods

fold :: Monoid m => Validation e m -> m #

foldMap :: Monoid m => (a -> m) -> Validation e a -> m #

foldMap' :: Monoid m => (a -> m) -> Validation e a -> m #

foldr :: (a -> b -> b) -> b -> Validation e a -> b #

foldr' :: (a -> b -> b) -> b -> Validation e a -> b #

foldl :: (b -> a -> b) -> b -> Validation e a -> b #

foldl' :: (b -> a -> b) -> b -> Validation e a -> b #

foldr1 :: (a -> a -> a) -> Validation e a -> a #

foldl1 :: (a -> a -> a) -> Validation e a -> a #

toList :: Validation e a -> [a] #

null :: Validation e a -> Bool #

length :: Validation e a -> Int #

elem :: Eq a => a -> Validation e a -> Bool #

maximum :: Ord a => Validation e a -> a #

minimum :: Ord a => Validation e a -> a #

sum :: Num a => Validation e a -> a #

product :: Num a => Validation e a -> a #

Traversable (Validation e)

Traverse values inside Success with some effectful computation.

Examples

>>> parseInt = readMaybe :: String -> Maybe Int
>>> traverse parseInt (Success "42")
Just (Success 42)
>>> traverse parseInt (Success "int")
Nothing
>>> traverse parseInt (Failure ["42"])
Just (Failure ["42"])
Instance details

Defined in Validation

Methods

traverse :: Applicative f => (a -> f b) -> Validation e a -> f (Validation e b) #

sequenceA :: Applicative f => Validation e (f a) -> f (Validation e a) #

mapM :: Monad m => (a -> m b) -> Validation e a -> m (Validation e b) #

sequence :: Monad m => Validation e (m a) -> m (Validation e a) #

Monoid e => Alternative (Validation e)

This instance implements the behaviour when the first Success is returned. Otherwise all Failures are combined.

Examples

>>> success1 = Success [9] :: Validation [String] [Int]
>>> success2 = Success [15] :: Validation [String] [Int]
>>> failure1 = Failure ["WRONG"] :: Validation [String] [Int]
>>> failure2 = Failure ["FAIL"]  :: Validation [String] [Int]
>>> success1 <|> success2
Success [9]
>>> failure1 <|> failure2
Failure ["WRONG","FAIL"]
>>> failure2 <|> success2
Success [15]
Instance details

Defined in Validation

Methods

empty :: Validation e a #

(<|>) :: Validation e a -> Validation e a -> Validation e a #

some :: Validation e a -> Validation e [a] #

many :: Validation e a -> Validation e [a] #

Semigroup e => Applicative (Validation e)

This instance is the most important instance for the Validation data type. It's responsible for the many implementations. And it allows to accumulate errors while performing validation or combining the results in the applicative style.

Examples

>>> success1 = Success 9 :: Validation [String] Int
>>> success2 = Success 15 :: Validation [String] Int
>>> successF = Success (* 2) :: Validation [String] (Int -> Int)
>>> failure1 = Failure ["WRONG"] :: Validation [String] Int
>>> failure2 = Failure ["FAIL"]  :: Validation [String] Int
>>> successF <*> success1
Success 18
>>> successF <*> failure1
Failure ["WRONG"]
>>> (+) <$> success1 <*> success2
Success 24
>>> (+) <$> failure1 <*> failure2
Failure ["WRONG","FAIL"]
>>> liftA2 (+) success1 failure1
Failure ["WRONG"]
>>> liftA3 (,,) failure1 success1 failure2
Failure ["WRONG","FAIL"]

Implementations of all functions are lazy and they correctly work if some arguments are not fully evaluated.

>>> failure1 *> failure2
Failure ["WRONG","FAIL"]
>>> isFailure $ failure1 *> failure2
True
>>> epicFail = error "Impossible validation" :: Validation [String] Int
>>> isFailure $ failure1 *> epicFail
True
Instance details

Defined in Validation

Methods

pure :: a -> Validation e a #

(<*>) :: Validation e (a -> b) -> Validation e a -> Validation e b #

liftA2 :: (a -> b -> c) -> Validation e a -> Validation e b -> Validation e c #

(*>) :: Validation e a -> Validation e b -> Validation e b #

(<*) :: Validation e a -> Validation e b -> Validation e a #

Functor (Validation e)

Allows changing the value inside Success with a given function.

Examples

>>> fmap (+1) (Success 9)
Success 10
>>> fmap (+1) (Failure ["wrong"])
Failure ["wrong"]
Instance details

Defined in Validation

Methods

fmap :: (a -> b) -> Validation e a -> Validation e b #

(<$) :: a -> Validation e b -> Validation e a #

(NoValidationMonadError, Semigroup e) => Monad (Validation e)

⚠️CAUTION⚠️ This instance is for custom error display only.

It's not possible to implement lawful Monad instance for Validation.

In case it is used by mistake, the user will see the following:

>>> Success 42 >>= \n -> if even n then Success n else Failure ["Not even"]
...
... Type 'Validation' doesn't have lawful 'Monad' instance
      which means that you can't use 'Monad' methods with 'Validation'.
...
Instance details

Defined in Validation

Methods

(>>=) :: Validation e a -> (a -> Validation e b) -> Validation e b #

(>>) :: Validation e a -> Validation e b -> Validation e b #

return :: a -> Validation e a #

NFData e => NFData1 (Validation e) 
Instance details

Defined in Validation

Methods

liftRnf :: (a -> ()) -> Validation e a -> () #

Semigroup e => Selective (Validation e)

Selective functors from the selective package. This instance allows choosing which validations to apply based on value inside. Validation can't have a lawful Monad instance but it's highly desirable to have the monadic behavior in cases when you want future checks depend on previous values. Selective allows to circumvent this limitation by providing the desired behavior.

Examples

Expand

To understand better, how Selective can be helpful, let's consider a typical usage example with validating passwords.

>>> :{
newtype Password = Password
    { unPassword :: String
    } deriving stock (Show)
:}

When user enters a password in some form, we want to check the following conditions:

  1. Password must not be empty.
  2. Password must contain at least 8 characters.
  3. Password must contain at least 1 digit.

As in the previous usage example with form validation, let's introduce a custom data type to represent all possible errors.

>>> :{
data PasswordValidationError
    = EmptyPassword
    | ShortPassword
    | NoDigitPassword
    deriving stock (Show)
:}

And, again, we can implement independent functions to validate all these cases:

>>> type PasswordValidation = Validation (NonEmpty PasswordValidationError) Password
>>> :{
validateEmptyPassword :: String -> PasswordValidation
validateEmptyPassword password = Password password <$
    failureIf (null password) EmptyPassword
:}
>>> :{
validateShortPassword :: String -> PasswordValidation
validateShortPassword password = Password password <$
    failureIf (length password < 8) ShortPassword
:}
>>> :{
validatePasswordDigit :: String -> PasswordValidation
validatePasswordDigit password = Password password <$
    failureUnless (any isDigit password) NoDigitPassword
:}

And we can easily compose all these checks into single validation for Password using Applicative instance:

>>> :{
validatePassword :: String -> PasswordValidation
validatePassword password =
    validateEmptyPassword password
    *> validateShortPassword password
    *> validatePasswordDigit password
:}

However, if we try using this function, we can notice a problem immediately:

>>> validatePassword ""
Failure (EmptyPassword :| [ShortPassword,NoDigitPassword])

Due to the nature of the Applicative instance for Validation, we run all checks and combine all possible errors. But you can notice that if password is empty, it doesn't make sense to run other validations. The fact that the password is empty implies that password is shorter than 8 characters.

You may say that check for empty password is redundant because empty password is a special case of a short password. However, when using Validation, we want to display readable and friendly errors to users, so they know how to fix errors and can act correspondingly.

This behaviour could be achieved easily if Validation had the Monad instance. But it can't have a lawful Monad instance. Fortunately, the Selective instance for Validation can help with our problem. But to solve it, we need to write our password validation in a slightly different way.

First, we need to write a function that checks whether the password is empty:

>>> :{
checkEmptyPassword :: String -> Validation e Bool
checkEmptyPassword = Success . null
:}

Now we can use the ifS function from the selective package to branch on the result of checkEmptyPassword:

>>> :{
validatePassword :: String -> PasswordValidation
validatePassword password = ifS
    (checkEmptyPassword password)
    (failure EmptyPassword)
    (validateShortPassword password *> validatePasswordDigit password)
:}

With this implementation we achieved our desired behavior:

>>> validatePassword ""
Failure (EmptyPassword :| [])
>>> validatePassword "abc"
Failure (ShortPassword :| [NoDigitPassword])
>>> validatePassword "abc123"
Failure (ShortPassword :| [])
>>> validatePassword "security567"
Success (Password {unPassword = "security567"})
Instance details

Defined in Validation

Methods

select :: Validation e (Either a b) -> Validation e (a -> b) -> Validation e b #

(Data e, Data a) => Data (Validation e a) 
Instance details

Defined in Validation

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Validation e a -> c (Validation e a) #

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Validation e a) #

toConstr :: Validation e a -> Constr #

dataTypeOf :: Validation e a -> DataType #

dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Validation e a)) #

dataCast2 :: Typeable t => (forall d e0. (Data d, Data e0) => c (t d e0)) -> Maybe (c (Validation e a)) #

gmapT :: (forall b. Data b => b -> b) -> Validation e a -> Validation e a #

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Validation e a -> r #

gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Validation e a -> r #

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

gmapQi :: Int -> (forall d. Data d => d -> u) -> Validation e a -> u #

gmapM :: Monad m => (forall d. Data d => d -> m d) -> Validation e a -> m (Validation e a) #

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Validation e a -> m (Validation e a) #

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Validation e a -> m (Validation e a) #

(Semigroup e, Monoid a) => Monoid (Validation e a)

mempty :: Validation e a is Success which stores mempty :: a to be consistent with the Semigroup instance.

Examples

>>> mempty :: Validation String [Bool]
Success []
Instance details

Defined in Validation

Methods

mempty :: Validation e a #

mappend :: Validation e a -> Validation e a -> Validation e a #

mconcat :: [Validation e a] -> Validation e a #

(Semigroup e, Semigroup a) => Semigroup (Validation e a)

Semigroup allows merging multiple Validations into single one by combining values inside both Failure and Success. The <> operator merges two Validations following the below rules:

  1. If both values are Failures, returns a new Failure with accumulated errors.
  2. If both values are Successful, returns a new Success with combined success using Semigroup for values inside Success.
  3. If one value is Failure and another one is Success, then Failure is returned.

Examples

>>> success1 = Success [9] :: Validation [String] [Int]
>>> success2 = Success [15] :: Validation [String] [Int]
>>> failure1 = Failure ["WRONG"] :: Validation [String] [Int]
>>> failure2 = Failure ["FAIL"]  :: Validation [String] [Int]
>>> success1 <> success2
Success [9,15]
>>> failure1 <> failure2
Failure ["WRONG","FAIL"]
>>> success1 <> failure1
Failure ["WRONG"]
>>> failure2 <> success1 <> success2 <> failure1
Failure ["FAIL","WRONG"]
Instance details

Defined in Validation

Methods

(<>) :: Validation e a -> Validation e a -> Validation e a #

sconcat :: NonEmpty (Validation e a) -> Validation e a #

stimes :: Integral b => b -> Validation e a -> Validation e a #

Generic (Validation e a) 
Instance details

Defined in Validation

Associated Types

type Rep (Validation e a) :: Type -> Type #

Methods

from :: Validation e a -> Rep (Validation e a) x #

to :: Rep (Validation e a) x -> Validation e a #

(Show e, Show a) => Show (Validation e a) 
Instance details

Defined in Validation

Methods

showsPrec :: Int -> Validation e a -> ShowS #

show :: Validation e a -> String #

showList :: [Validation e a] -> ShowS #

(NFData e, NFData a) => NFData (Validation e a) 
Instance details

Defined in Validation

Methods

rnf :: Validation e a -> () #

(Eq e, Eq a) => Eq (Validation e a) 
Instance details

Defined in Validation

Methods

(==) :: Validation e a -> Validation e a -> Bool #

(/=) :: Validation e a -> Validation e a -> Bool #

(Ord e, Ord a) => Ord (Validation e a) 
Instance details

Defined in Validation

Methods

compare :: Validation e a -> Validation e a -> Ordering #

(<) :: Validation e a -> Validation e a -> Bool #

(<=) :: Validation e a -> Validation e a -> Bool #

(>) :: Validation e a -> Validation e a -> Bool #

(>=) :: Validation e a -> Validation e a -> Bool #

max :: Validation e a -> Validation e a -> Validation e a #

min :: Validation e a -> Validation e a -> Validation e a #

type Rep1 (Validation e :: Type -> Type) 
Instance details

Defined in Validation

type Rep1 (Validation e :: Type -> Type) = D1 ('MetaData "Validation" "Validation" "validation-selective-0.2.0.0-5nF29cXFH7PKs0yF5r81Yo" 'False) (C1 ('MetaCons "Failure" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 e)) :+: C1 ('MetaCons "Success" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) Par1))
type Rep (Validation e a) 
Instance details

Defined in Validation

type Rep (Validation e a) = D1 ('MetaData "Validation" "Validation" "validation-selective-0.2.0.0-5nF29cXFH7PKs0yF5r81Yo" 'False) (C1 ('MetaCons "Failure" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 e)) :+: C1 ('MetaCons "Success" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 a)))

failure :: e -> Validation (NonEmpty e) a #

Create a Failure of NonEmpty list with a single given error.

>>> failure "I am a failure"
Failure ("I am a failure" :| [])

successes :: [Validation e a] -> [a] #

Filters out all Success values into the new list of as from the given list of Validations.

Note that the order is preserved.

>>> successes [Failure "Hello", Success 1, Failure "world", Success 2, Failure "!" ]
[1,2]

failures :: [Validation e a] -> [e] #

Filters out all Failure values into the new list of es from the given list of Validations.

Note that the order is preserved.

>>> failures [Failure "Hello", Success 1, Failure "world", Success 2, Failure "!" ]
["Hello","world","!"]

traverseValidate :: forall t a err b. Traversable t => (a -> Either err b) -> t a -> Either (NonEmpty err) (t b) Source #

traverse with a function returning Either and collect all errors that happen, if they happen.

Does not shortcut on error, so will always traverse the whole list/Traversable structure.

This is a useful error handling function in many circumstances, because it won’t only return the first error that happens, but rather all of them.

traverseValidateM :: forall t m a err b. (Traversable t, Applicative m) => (a -> m (Either err b)) -> t a -> m (Either (NonEmpty err) (t b)) Source #

traverse with a function returning 'm Either' and collect all errors that happen, if they happen.

Does not shortcut on error, so will always traverse the whole list/Traversable structure.

This is a useful error handling function in many circumstances, because it won’t only return the first error that happens, but rather all of them.

traverseValidateM_ :: forall t m a err. (Traversable t, Applicative m) => (a -> m (Either err ())) -> t a -> m (Either (NonEmpty err) ()) Source #

traverse_ with a function returning 'm Either' and collect all errors that happen, if they happen.

Does not shortcut on error, so will always traverse the whole list/Traversable structure.

This is a useful error handling function in many circumstances, because it won’t only return the first error that happens, but rather all of them.

eitherToValidation :: Either e a -> Validation e a #

Transform an Either into a Validation.

>>> eitherToValidation (Right "whoop")
Success "whoop"
>>> eitherToValidation (Left "nahh")
Failure "nahh"

eitherToListValidation :: Either a c -> Validation (NonEmpty a) c Source #

Like eitherToValidation, but puts the Error side into a NonEmpty list to make it combine with other validations.

See also validateEithers, if you have a list of Either and want to collect all errors.

validationToEither :: Validation e a -> Either e a #

Transform a Validation into an Either.

>>> validationToEither (Success "whoop")
Right "whoop"
>>> validationToEither (Failure "nahh")
Left "nahh"

data These a b #

The These type represents values with two non-exclusive possibilities.

This can be useful to represent combinations of two values, where the combination is defined if either input is. Algebraically, the type These A B represents (A + B + AB), which doesn't factor easily into sums and products--a type like Either A (B, Maybe A) is unclear and awkward to use.

These has straightforward instances of Functor, Monad, &c., and behaves like a hybrid error/writer monad, as would be expected.

For zipping and unzipping of structures with These values, see Data.Align.

Constructors

This a 
That b 
These a b 

Instances

Instances details
Assoc These

Since: these-0.8

Instance details

Defined in Data.These

Methods

assoc :: These (These a b) c -> These a (These b c) #

unassoc :: These a (These b c) -> These (These a b) c #

Swap These

Since: these-0.8

Instance details

Defined in Data.These

Methods

swap :: These a b -> These b a #

Bifoldable These 
Instance details

Defined in Data.These

Methods

bifold :: Monoid m => These m m -> m #

bifoldMap :: Monoid m => (a -> m) -> (b -> m) -> These a b -> m #

bifoldr :: (a -> c -> c) -> (b -> c -> c) -> c -> These a b -> c #

bifoldl :: (c -> a -> c) -> (c -> b -> c) -> c -> These a b -> c #

Bifunctor These 
Instance details

Defined in Data.These

Methods

bimap :: (a -> b) -> (c -> d) -> These a c -> These b d #

first :: (a -> b) -> These a c -> These b c #

second :: (b -> c) -> These a b -> These a c #

Bitraversable These 
Instance details

Defined in Data.These

Methods

bitraverse :: Applicative f => (a -> f c) -> (b -> f d) -> These a b -> f (These c d) #

Eq2 These

Since: these-1.1.1

Instance details

Defined in Data.These

Methods

liftEq2 :: (a -> b -> Bool) -> (c -> d -> Bool) -> These a c -> These b d -> Bool #

Ord2 These

Since: these-1.1.1

Instance details

Defined in Data.These

Methods

liftCompare2 :: (a -> b -> Ordering) -> (c -> d -> Ordering) -> These a c -> These b d -> Ordering #

Read2 These

Since: these-1.1.1

Instance details

Defined in Data.These

Methods

liftReadsPrec2 :: (Int -> ReadS a) -> ReadS [a] -> (Int -> ReadS b) -> ReadS [b] -> Int -> ReadS (These a b) #

liftReadList2 :: (Int -> ReadS a) -> ReadS [a] -> (Int -> ReadS b) -> ReadS [b] -> ReadS [These a b] #

liftReadPrec2 :: ReadPrec a -> ReadPrec [a] -> ReadPrec b -> ReadPrec [b] -> ReadPrec (These a b) #

liftReadListPrec2 :: ReadPrec a -> ReadPrec [a] -> ReadPrec b -> ReadPrec [b] -> ReadPrec [These a b] #

Show2 These

Since: these-1.1.1

Instance details

Defined in Data.These

Methods

liftShowsPrec2 :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> (Int -> b -> ShowS) -> ([b] -> ShowS) -> Int -> These a b -> ShowS #

liftShowList2 :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> (Int -> b -> ShowS) -> ([b] -> ShowS) -> [These a b] -> ShowS #

NFData2 These

Since: these-1.1.1

Instance details

Defined in Data.These

Methods

liftRnf2 :: (a -> ()) -> (b -> ()) -> These a b -> () #

Bifoldable1 These

Since: these-1.2

Instance details

Defined in Data.These

Methods

bifold1 :: Semigroup m => These m m -> m #

bifoldMap1 :: Semigroup m => (a -> m) -> (b -> m) -> These a b -> m #

Hashable2 These

Since: these-1.1.1

Instance details

Defined in Data.These

Methods

liftHashWithSalt2 :: (Int -> a -> Int) -> (Int -> b -> Int) -> Int -> These a b -> Int #

Generic1 (These a :: Type -> Type) 
Instance details

Defined in Data.These

Associated Types

type Rep1 (These a) :: k -> Type #

Methods

from1 :: forall (a0 :: k). These a a0 -> Rep1 (These a) a0 #

to1 :: forall (a0 :: k). Rep1 (These a) a0 -> These a a0 #

Foldable (These a) 
Instance details

Defined in Data.These

Methods

fold :: Monoid m => These a m -> m #

foldMap :: Monoid m => (a0 -> m) -> These a a0 -> m #

foldMap' :: Monoid m => (a0 -> m) -> These a a0 -> m #

foldr :: (a0 -> b -> b) -> b -> These a a0 -> b #

foldr' :: (a0 -> b -> b) -> b -> These a a0 -> b #

foldl :: (b -> a0 -> b) -> b -> These a a0 -> b #

foldl' :: (b -> a0 -> b) -> b -> These a a0 -> b #

foldr1 :: (a0 -> a0 -> a0) -> These a a0 -> a0 #

foldl1 :: (a0 -> a0 -> a0) -> These a a0 -> a0 #

toList :: These a a0 -> [a0] #

null :: These a a0 -> Bool #

length :: These a a0 -> Int #

elem :: Eq a0 => a0 -> These a a0 -> Bool #

maximum :: Ord a0 => These a a0 -> a0 #

minimum :: Ord a0 => These a a0 -> a0 #

sum :: Num a0 => These a a0 -> a0 #

product :: Num a0 => These a a0 -> a0 #

Eq a => Eq1 (These a)

Since: these-1.1.1

Instance details

Defined in Data.These

Methods

liftEq :: (a0 -> b -> Bool) -> These a a0 -> These a b -> Bool #

Ord a => Ord1 (These a)

Since: these-1.1.1

Instance details

Defined in Data.These

Methods

liftCompare :: (a0 -> b -> Ordering) -> These a a0 -> These a b -> Ordering #

Read a => Read1 (These a)

Since: these-1.1.1

Instance details

Defined in Data.These

Methods

liftReadsPrec :: (Int -> ReadS a0) -> ReadS [a0] -> Int -> ReadS (These a a0) #

liftReadList :: (Int -> ReadS a0) -> ReadS [a0] -> ReadS [These a a0] #

liftReadPrec :: ReadPrec a0 -> ReadPrec [a0] -> ReadPrec (These a a0) #

liftReadListPrec :: ReadPrec a0 -> ReadPrec [a0] -> ReadPrec [These a a0] #

Show a => Show1 (These a)

Since: these-1.1.1

Instance details

Defined in Data.These

Methods

liftShowsPrec :: (Int -> a0 -> ShowS) -> ([a0] -> ShowS) -> Int -> These a a0 -> ShowS #

liftShowList :: (Int -> a0 -> ShowS) -> ([a0] -> ShowS) -> [These a a0] -> ShowS #

Traversable (These a) 
Instance details

Defined in Data.These

Methods

traverse :: Applicative f => (a0 -> f b) -> These a a0 -> f (These a b) #

sequenceA :: Applicative f => These a (f a0) -> f (These a a0) #

mapM :: Monad m => (a0 -> m b) -> These a a0 -> m (These a b) #

sequence :: Monad m => These a (m a0) -> m (These a a0) #

Semigroup a => Applicative (These a) 
Instance details

Defined in Data.These

Methods

pure :: a0 -> These a a0 #

(<*>) :: These a (a0 -> b) -> These a a0 -> These a b #

liftA2 :: (a0 -> b -> c) -> These a a0 -> These a b -> These a c #

(*>) :: These a a0 -> These a b -> These a b #

(<*) :: These a a0 -> These a b -> These a a0 #

Functor (These a) 
Instance details

Defined in Data.These

Methods

fmap :: (a0 -> b) -> These a a0 -> These a b #

(<$) :: a0 -> These a b -> These a a0 #

Semigroup a => Monad (These a) 
Instance details

Defined in Data.These

Methods

(>>=) :: These a a0 -> (a0 -> These a b) -> These a b #

(>>) :: These a a0 -> These a b -> These a b #

return :: a0 -> These a a0 #

NFData a => NFData1 (These a)

Since: these-1.1.1

Instance details

Defined in Data.These

Methods

liftRnf :: (a0 -> ()) -> These a a0 -> () #

Hashable a => Hashable1 (These a)

Since: these-1.1.1

Instance details

Defined in Data.These

Methods

liftHashWithSalt :: (Int -> a0 -> Int) -> Int -> These a a0 -> Int #

(Data a, Data b) => Data (These a b) 
Instance details

Defined in Data.These

Methods

gfoldl :: (forall d b0. Data d => c (d -> b0) -> d -> c b0) -> (forall g. g -> c g) -> These a b -> c (These a b) #

gunfold :: (forall b0 r. Data b0 => c (b0 -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (These a b) #

toConstr :: These a b -> Constr #

dataTypeOf :: These a b -> DataType #

dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (These a b)) #

dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (These a b)) #

gmapT :: (forall b0. Data b0 => b0 -> b0) -> These a b -> These a b #

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> These a b -> r #

gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> These a b -> r #

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

gmapQi :: Int -> (forall d. Data d => d -> u) -> These a b -> u #

gmapM :: Monad m => (forall d. Data d => d -> m d) -> These a b -> m (These a b) #

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> These a b -> m (These a b) #

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> These a b -> m (These a b) #

(Semigroup a, Semigroup b) => Semigroup (These a b) 
Instance details

Defined in Data.These

Methods

(<>) :: These a b -> These a b -> These a b #

sconcat :: NonEmpty (These a b) -> These a b #

stimes :: Integral b0 => b0 -> These a b -> These a b #

Generic (These a b) 
Instance details

Defined in Data.These

Associated Types

type Rep (These a b) :: Type -> Type #

Methods

from :: These a b -> Rep (These a b) x #

to :: Rep (These a b) x -> These a b #

(Read a, Read b) => Read (These a b) 
Instance details

Defined in Data.These

(Show a, Show b) => Show (These a b) 
Instance details

Defined in Data.These

Methods

showsPrec :: Int -> These a b -> ShowS #

show :: These a b -> String #

showList :: [These a b] -> ShowS #

(Binary a, Binary b) => Binary (These a b)

Since: these-0.7.1

Instance details

Defined in Data.These

Methods

put :: These a b -> Put #

get :: Get (These a b) #

putList :: [These a b] -> Put #

(NFData a, NFData b) => NFData (These a b)

Since: these-0.7.1

Instance details

Defined in Data.These

Methods

rnf :: These a b -> () #

(Eq a, Eq b) => Eq (These a b) 
Instance details

Defined in Data.These

Methods

(==) :: These a b -> These a b -> Bool #

(/=) :: These a b -> These a b -> Bool #

(Ord a, Ord b) => Ord (These a b) 
Instance details

Defined in Data.These

Methods

compare :: These a b -> These a b -> Ordering #

(<) :: These a b -> These a b -> Bool #

(<=) :: These a b -> These a b -> Bool #

(>) :: These a b -> These a b -> Bool #

(>=) :: These a b -> These a b -> Bool #

max :: These a b -> These a b -> These a b #

min :: These a b -> These a b -> These a b #

(Hashable a, Hashable b) => Hashable (These a b) 
Instance details

Defined in Data.These

Methods

hashWithSalt :: Int -> These a b -> Int #

hash :: These a b -> Int #

type Rep1 (These a :: Type -> Type) 
Instance details

Defined in Data.These

type Rep (These a b) 
Instance details

Defined in Data.These

eitherToThese :: Either err a -> These err a Source #

Convert an Either to a These.

eitherToListThese :: Either err a -> These (NonEmpty err) a Source #

Like eitherToThese, but puts the Error side into a NonEmpty list to make it combine with other theses.

validationToThese :: Validation err a -> These err a Source #

Convert a Validation to a These.

thenThese :: (Monad m, Semigroup err) => (a -> m (These err b)) -> m (These err a) -> m (These err b) Source #

Nested >>= of a These inside some other m.

Use if you want to collect errors and successes, and want to chain multiple function returning These.

thenValidate :: Monad m => (a -> m (Validation err b)) -> m (Validation err a) -> m (Validation err b) Source #

Nested validating bind-like combinator inside some other m.

Use if you want to collect errors, and want to chain multiple functions returning Validation.

data NonEmpty a #

Non-empty (and non-strict) list type.

Since: base-4.9.0.0

Constructors

a :| [a] infixr 5 

Instances

Instances details
Foldable NonEmpty

Since: base-4.9.0.0

Instance details

Defined in Data.Foldable

Methods

fold :: Monoid m => NonEmpty m -> m #

foldMap :: Monoid m => (a -> m) -> NonEmpty a -> m #

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

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

foldr' :: (a -> b -> b) -> b -> NonEmpty a -> b #

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

foldl' :: (b -> a -> b) -> b -> NonEmpty a -> b #

foldr1 :: (a -> a -> a) -> NonEmpty a -> a #

foldl1 :: (a -> a -> a) -> NonEmpty a -> a #

toList :: NonEmpty a -> [a] #

null :: NonEmpty a -> Bool #

length :: NonEmpty a -> Int #

elem :: Eq a => a -> NonEmpty a -> Bool #

maximum :: Ord a => NonEmpty a -> a #

minimum :: Ord a => NonEmpty a -> a #

sum :: Num a => NonEmpty a -> a #

product :: Num a => NonEmpty a -> a #

Eq1 NonEmpty

Since: base-4.10.0.0

Instance details

Defined in Data.Functor.Classes

Methods

liftEq :: (a -> b -> Bool) -> NonEmpty a -> NonEmpty b -> Bool #

Ord1 NonEmpty

Since: base-4.10.0.0

Instance details

Defined in Data.Functor.Classes

Methods

liftCompare :: (a -> b -> Ordering) -> NonEmpty a -> NonEmpty b -> Ordering #

Read1 NonEmpty

Since: base-4.10.0.0

Instance details

Defined in Data.Functor.Classes

Methods

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

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

liftReadPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec (NonEmpty a) #

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

Show1 NonEmpty

Since: base-4.10.0.0

Instance details

Defined in Data.Functor.Classes

Methods

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

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

Traversable NonEmpty

Since: base-4.9.0.0

Instance details

Defined in Data.Traversable

Methods

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

sequenceA :: Applicative f => NonEmpty (f a) -> f (NonEmpty a) #

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

sequence :: Monad m => NonEmpty (m a) -> m (NonEmpty a) #

Applicative NonEmpty

Since: base-4.9.0.0

Instance details

Defined in GHC.Base

Methods

pure :: a -> NonEmpty a #

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

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

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

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

Functor NonEmpty

Since: base-4.9.0.0

Instance details

Defined in GHC.Base

Methods

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

(<$) :: a -> NonEmpty b -> NonEmpty a #

Monad NonEmpty

Since: base-4.9.0.0

Instance details

Defined in GHC.Base

Methods

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

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

return :: a -> NonEmpty a #

Comonad NonEmpty 
Instance details

Defined in Control.Comonad

Methods

extract :: NonEmpty a -> a #

duplicate :: NonEmpty a -> NonEmpty (NonEmpty a) #

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

ComonadApply NonEmpty 
Instance details

Defined in Control.Comonad

Methods

(<@>) :: NonEmpty (a -> b) -> NonEmpty a -> NonEmpty b #

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

(<@) :: NonEmpty a -> NonEmpty b -> NonEmpty a #

Foldable1 NonEmpty 
Instance details

Defined in Data.Foldable1

Methods

fold1 :: Semigroup m => NonEmpty m -> m #

foldMap1 :: Semigroup m => (a -> m) -> NonEmpty a -> m #

foldMap1' :: Semigroup m => (a -> m) -> NonEmpty a -> m #

toNonEmpty :: NonEmpty a -> NonEmpty a #

maximum :: Ord a => NonEmpty a -> a #

minimum :: Ord a => NonEmpty a -> a #

head :: NonEmpty a -> a #

last :: NonEmpty a -> a #

foldrMap1 :: (a -> b) -> (a -> b -> b) -> NonEmpty a -> b #

foldlMap1' :: (a -> b) -> (b -> a -> b) -> NonEmpty a -> b #

foldlMap1 :: (a -> b) -> (b -> a -> b) -> NonEmpty a -> b #

foldrMap1' :: (a -> b) -> (a -> b -> b) -> NonEmpty a -> b #

Hashable1 NonEmpty

Since: hashable-1.3.1.0

Instance details

Defined in Data.Hashable.Class

Methods

liftHashWithSalt :: (Int -> a -> Int) -> Int -> NonEmpty a -> Int #

Alt NonEmpty 
Instance details

Defined in Data.Functor.Alt

Apply NonEmpty 
Instance details

Defined in Data.Functor.Bind.Class

Methods

(<.>) :: NonEmpty (a -> b) -> NonEmpty a -> NonEmpty b #

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

(<.) :: NonEmpty a -> NonEmpty b -> NonEmpty a #

liftF2 :: (a -> b -> c) -> NonEmpty a -> NonEmpty b -> NonEmpty c #

Bind NonEmpty 
Instance details

Defined in Data.Functor.Bind.Class

Methods

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

join :: NonEmpty (NonEmpty a) -> NonEmpty a #

Extend NonEmpty 
Instance details

Defined in Data.Functor.Extend

Methods

duplicated :: NonEmpty a -> NonEmpty (NonEmpty a) #

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

Traversable1 NonEmpty 
Instance details

Defined in Data.Semigroup.Traversable.Class

Methods

traverse1 :: Apply f => (a -> f b) -> NonEmpty a -> f (NonEmpty b) #

sequence1 :: Apply f => NonEmpty (f b) -> f (NonEmpty b) #

Generic1 NonEmpty 
Instance details

Defined in GHC.Generics

Associated Types

type Rep1 NonEmpty :: k -> Type #

Methods

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

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

Lift a => Lift (NonEmpty a :: Type)

Since: template-haskell-2.15.0.0

Instance details

Defined in Language.Haskell.TH.Syntax

Methods

lift :: Quote m => NonEmpty a -> m Exp #

liftTyped :: forall (m :: Type -> Type). Quote m => NonEmpty a -> Code m (NonEmpty a) #

Data a => Data (NonEmpty a)

Since: base-4.9.0.0

Instance details

Defined in Data.Data

Methods

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

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

toConstr :: NonEmpty a -> Constr #

dataTypeOf :: NonEmpty a -> DataType #

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

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

gmapT :: (forall b. Data b => b -> b) -> NonEmpty a -> NonEmpty a #

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> NonEmpty a -> r #

gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> NonEmpty a -> r #

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

gmapQi :: Int -> (forall d. Data d => d -> u) -> NonEmpty a -> u #

gmapM :: Monad m => (forall d. Data d => d -> m d) -> NonEmpty a -> m (NonEmpty a) #

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> NonEmpty a -> m (NonEmpty a) #

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> NonEmpty a -> m (NonEmpty a) #

Semigroup (NonEmpty a)

Since: base-4.9.0.0

Instance details

Defined in GHC.Base

Methods

(<>) :: NonEmpty a -> NonEmpty a -> NonEmpty a #

sconcat :: NonEmpty (NonEmpty a) -> NonEmpty a #

stimes :: Integral b => b -> NonEmpty a -> NonEmpty a #

IsList (NonEmpty a)

Since: base-4.9.0.0

Instance details

Defined in GHC.Exts

Associated Types

type Item (NonEmpty a) #

Methods

fromList :: [Item (NonEmpty a)] -> NonEmpty a #

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

toList :: NonEmpty a -> [Item (NonEmpty a)] #

Generic (NonEmpty a) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (NonEmpty a) :: Type -> Type #

Methods

from :: NonEmpty a -> Rep (NonEmpty a) x #

to :: Rep (NonEmpty a) x -> NonEmpty a #

Read a => Read (NonEmpty a)

Since: base-4.11.0.0

Instance details

Defined in GHC.Read

Show a => Show (NonEmpty a)

Since: base-4.11.0.0

Instance details

Defined in GHC.Show

Methods

showsPrec :: Int -> NonEmpty a -> ShowS #

show :: NonEmpty a -> String #

showList :: [NonEmpty a] -> ShowS #

Outputable a => Outputable (NonEmpty a) 
Instance details

Defined in GHC.Utils.Outputable

Methods

ppr :: NonEmpty a -> SDoc #

Eq a => Eq (NonEmpty a)

Since: base-4.9.0.0

Instance details

Defined in GHC.Base

Methods

(==) :: NonEmpty a -> NonEmpty a -> Bool #

(/=) :: NonEmpty a -> NonEmpty a -> Bool #

Ord a => Ord (NonEmpty a)

Since: base-4.9.0.0

Instance details

Defined in GHC.Base

Methods

compare :: NonEmpty a -> NonEmpty a -> Ordering #

(<) :: NonEmpty a -> NonEmpty a -> Bool #

(<=) :: NonEmpty a -> NonEmpty a -> Bool #

(>) :: NonEmpty a -> NonEmpty a -> Bool #

(>=) :: NonEmpty a -> NonEmpty a -> Bool #

max :: NonEmpty a -> NonEmpty a -> NonEmpty a #

min :: NonEmpty a -> NonEmpty a -> NonEmpty a #

Hashable a => Hashable (NonEmpty a) 
Instance details

Defined in Data.Hashable.Class

Methods

hashWithSalt :: Int -> NonEmpty a -> Int #

hash :: NonEmpty a -> Int #

type Rep1 NonEmpty

Since: base-4.6.0.0

Instance details

Defined in GHC.Generics

type Item (NonEmpty a) 
Instance details

Defined in GHC.Exts

type Item (NonEmpty a) = a
type Rep (NonEmpty a)

Since: base-4.6.0.0

Instance details

Defined in GHC.Generics

singleton :: a -> NonEmpty a Source #

Single element in a (non-empty) list.

nonEmpty :: [a] -> Maybe (NonEmpty a) #

nonEmpty efficiently turns a normal list into a NonEmpty stream, producing Nothing if the input is empty.

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

If the given list is empty, use the given default element and return a non-empty list.

toList :: Foldable t => t a -> [a] #

List of elements of a structure, from left to right. If the entire list is intended to be reduced via a fold, just fold the structure directly bypassing the list.

Examples

Expand

Basic usage:

>>> toList Nothing
[]
>>> toList (Just 42)
[42]
>>> toList (Left "foo")
[]
>>> toList (Node (Leaf 5) 17 (Node Empty 12 (Leaf 8)))
[5,17,12,8]

For lists, toList is the identity:

>>> toList [1, 2, 3]
[1,2,3]

Since: base-4.8.0.0

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

Construct a non-empty list, given a default value if the ist list was empty.

maximum1 :: (Foldable1 f, Ord a) => f a -> a Source #

O(n). Get the maximum element from a non-empty structure.

minimum1 :: (Foldable1 f, Ord a) => f a -> a Source #

O(n). Get the minimum element from a non-empty structure.

class Generic a #

Representable types of kind *. This class is derivable in GHC with the DeriveGeneric flag on.

A Generic instance must satisfy the following laws:

from . toid
to . fromid

Minimal complete definition

from, to

Instances

Instances details
Generic All 
Instance details

Defined in Data.Semigroup.Internal

Associated Types

type Rep All :: Type -> Type #

Methods

from :: All -> Rep All x #

to :: Rep All x -> All #

Generic Any 
Instance details

Defined in Data.Semigroup.Internal

Associated Types

type Rep Any :: Type -> Type #

Methods

from :: Any -> Rep Any x #

to :: Rep Any x -> Any #

Generic Void 
Instance details

Defined in Data.Void

Associated Types

type Rep Void :: Type -> Type #

Methods

from :: Void -> Rep Void x #

to :: Rep Void x -> Void #

Generic ByteOrder 
Instance details

Defined in GHC.ByteOrder

Associated Types

type Rep ByteOrder :: Type -> Type #

Generic Fingerprint 
Instance details

Defined in GHC.Generics

Associated Types

type Rep Fingerprint :: Type -> Type #

Generic Associativity 
Instance details

Defined in GHC.Generics

Associated Types

type Rep Associativity :: Type -> Type #

Generic DecidedStrictness 
Instance details

Defined in GHC.Generics

Associated Types

type Rep DecidedStrictness :: Type -> Type #

Generic Fixity 
Instance details

Defined in GHC.Generics

Associated Types

type Rep Fixity :: Type -> Type #

Methods

from :: Fixity -> Rep Fixity x #

to :: Rep Fixity x -> Fixity #

Generic SourceStrictness 
Instance details

Defined in GHC.Generics

Associated Types

type Rep SourceStrictness :: Type -> Type #

Generic SourceUnpackedness 
Instance details

Defined in GHC.Generics

Associated Types

type Rep SourceUnpackedness :: Type -> Type #

Generic ExitCode 
Instance details

Defined in GHC.IO.Exception

Associated Types

type Rep ExitCode :: Type -> Type #

Methods

from :: ExitCode -> Rep ExitCode x #

to :: Rep ExitCode x -> ExitCode #

Generic SrcLoc 
Instance details

Defined in GHC.Generics

Associated Types

type Rep SrcLoc :: Type -> Type #

Methods

from :: SrcLoc -> Rep SrcLoc x #

to :: Rep SrcLoc x -> SrcLoc #

Generic GCDetails 
Instance details

Defined in GHC.Stats

Associated Types

type Rep GCDetails :: Type -> Type #

Generic RTSStats 
Instance details

Defined in GHC.Stats

Associated Types

type Rep RTSStats :: Type -> Type #

Methods

from :: RTSStats -> Rep RTSStats x #

to :: Rep RTSStats x -> RTSStats #

Generic GeneralCategory 
Instance details

Defined in GHC.Generics

Associated Types

type Rep GeneralCategory :: Type -> Type #

Generic ForeignSrcLang 
Instance details

Defined in GHC.ForeignSrcLang.Type

Associated Types

type Rep ForeignSrcLang :: Type -> Type #

Generic Extension 
Instance details

Defined in GHC.LanguageExtensions.Type

Associated Types

type Rep Extension :: Type -> Type #

Generic ClosureType 
Instance details

Defined in GHC.Exts.Heap.ClosureTypes

Associated Types

type Rep ClosureType :: Type -> Type #

Generic PrimType 
Instance details

Defined in GHC.Exts.Heap.Closures

Associated Types

type Rep PrimType :: Type -> Type #

Methods

from :: PrimType -> Rep PrimType x #

to :: Rep PrimType x -> PrimType #

Generic TsoFlags 
Instance details

Defined in GHC.Exts.Heap.Closures

Associated Types

type Rep TsoFlags :: Type -> Type #

Methods

from :: TsoFlags -> Rep TsoFlags x #

to :: Rep TsoFlags x -> TsoFlags #

Generic WhatNext 
Instance details

Defined in GHC.Exts.Heap.Closures

Associated Types

type Rep WhatNext :: Type -> Type #

Methods

from :: WhatNext -> Rep WhatNext x #

to :: Rep WhatNext x -> WhatNext #

Generic WhyBlocked 
Instance details

Defined in GHC.Exts.Heap.Closures

Associated Types

type Rep WhyBlocked :: Type -> Type #

Generic StgInfoTable 
Instance details

Defined in GHC.Exts.Heap.InfoTable.Types

Associated Types

type Rep StgInfoTable :: Type -> Type #

Generic CostCentre 
Instance details

Defined in GHC.Exts.Heap.ProfInfo.Types

Associated Types

type Rep CostCentre :: Type -> Type #

Generic CostCentreStack 
Instance details

Defined in GHC.Exts.Heap.ProfInfo.Types

Associated Types

type Rep CostCentreStack :: Type -> Type #

Generic IndexTable 
Instance details

Defined in GHC.Exts.Heap.ProfInfo.Types

Associated Types

type Rep IndexTable :: Type -> Type #

Generic StgTSOProfInfo 
Instance details

Defined in GHC.Exts.Heap.ProfInfo.Types

Associated Types

type Rep StgTSOProfInfo :: Type -> Type #

Generic Ordering 
Instance details

Defined in GHC.Generics

Associated Types

type Rep Ordering :: Type -> Type #

Methods

from :: Ordering -> Rep Ordering x #

to :: Rep Ordering x -> Ordering #

Generic FFIConv 
Instance details

Defined in GHCi.FFI

Associated Types

type Rep FFIConv :: Type -> Type #

Methods

from :: FFIConv -> Rep FFIConv x #

to :: Rep FFIConv x -> FFIConv #

Generic FFIType 
Instance details

Defined in GHCi.FFI

Associated Types

type Rep FFIType :: Type -> Type #

Methods

from :: FFIType -> Rep FFIType x #

to :: Rep FFIType x -> FFIType #

Generic EvalOpts 
Instance details

Defined in GHCi.Message

Associated Types

type Rep EvalOpts :: Type -> Type #

Methods

from :: EvalOpts -> Rep EvalOpts x #

to :: Rep EvalOpts x -> EvalOpts #

Generic SerializableException 
Instance details

Defined in GHCi.Message

Associated Types

type Rep SerializableException :: Type -> Type #

Generic THResultType 
Instance details

Defined in GHCi.Message

Associated Types

type Rep THResultType :: Type -> Type #

Generic ResolvedBCO 
Instance details

Defined in GHCi.ResolvedBCO

Associated Types

type Rep ResolvedBCO :: Type -> Type #

Generic ResolvedBCOPtr 
Instance details

Defined in GHCi.ResolvedBCO

Associated Types

type Rep ResolvedBCOPtr :: Type -> Type #

Generic Mode 
Instance details

Defined in Text.PrettyPrint.Annotated.HughesPJ

Associated Types

type Rep Mode :: Type -> Type #

Methods

from :: Mode -> Rep Mode x #

to :: Rep Mode x -> Mode #

Generic Style 
Instance details

Defined in Text.PrettyPrint.Annotated.HughesPJ

Associated Types

type Rep Style :: Type -> Type #

Methods

from :: Style -> Rep Style x #

to :: Rep Style x -> Style #

Generic TextDetails 
Instance details

Defined in Text.PrettyPrint.Annotated.HughesPJ

Associated Types

type Rep TextDetails :: Type -> Type #

Generic Doc 
Instance details

Defined in Text.PrettyPrint.HughesPJ

Associated Types

type Rep Doc :: Type -> Type #

Methods

from :: Doc -> Rep Doc x #

to :: Rep Doc x -> Doc #

Generic AnnLookup 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep AnnLookup :: Type -> Type #

Generic AnnTarget 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep AnnTarget :: Type -> Type #

Generic Bang 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Bang :: Type -> Type #

Methods

from :: Bang -> Rep Bang x #

to :: Rep Bang x -> Bang #

Generic Body 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Body :: Type -> Type #

Methods

from :: Body -> Rep Body x #

to :: Rep Body x -> Body #

Generic Bytes 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Bytes :: Type -> Type #

Methods

from :: Bytes -> Rep Bytes x #

to :: Rep Bytes x -> Bytes #

Generic Callconv 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Callconv :: Type -> Type #

Methods

from :: Callconv -> Rep Callconv x #

to :: Rep Callconv x -> Callconv #

Generic Clause 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Clause :: Type -> Type #

Methods

from :: Clause -> Rep Clause x #

to :: Rep Clause x -> Clause #

Generic Con 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Con :: Type -> Type #

Methods

from :: Con -> Rep Con x #

to :: Rep Con x -> Con #

Generic Dec 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Dec :: Type -> Type #

Methods

from :: Dec -> Rep Dec x #

to :: Rep Dec x -> Dec #

Generic DecidedStrictness 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep DecidedStrictness :: Type -> Type #

Generic DerivClause 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep DerivClause :: Type -> Type #

Generic DerivStrategy 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep DerivStrategy :: Type -> Type #

Generic DocLoc 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep DocLoc :: Type -> Type #

Methods

from :: DocLoc -> Rep DocLoc x #

to :: Rep DocLoc x -> DocLoc #

Generic Exp 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Exp :: Type -> Type #

Methods

from :: Exp -> Rep Exp x #

to :: Rep Exp x -> Exp #

Generic FamilyResultSig 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep FamilyResultSig :: Type -> Type #

Generic Fixity 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Fixity :: Type -> Type #

Methods

from :: Fixity -> Rep Fixity x #

to :: Rep Fixity x -> Fixity #

Generic FixityDirection 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep FixityDirection :: Type -> Type #

Generic Foreign 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Foreign :: Type -> Type #

Methods

from :: Foreign -> Rep Foreign x #

to :: Rep Foreign x -> Foreign #

Generic FunDep 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep FunDep :: Type -> Type #

Methods

from :: FunDep -> Rep FunDep x #

to :: Rep FunDep x -> FunDep #

Generic Guard 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Guard :: Type -> Type #

Methods

from :: Guard -> Rep Guard x #

to :: Rep Guard x -> Guard #

Generic Info 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Info :: Type -> Type #

Methods

from :: Info -> Rep Info x #

to :: Rep Info x -> Info #

Generic InjectivityAnn 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep InjectivityAnn :: Type -> Type #

Generic Inline 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Inline :: Type -> Type #

Methods

from :: Inline -> Rep Inline x #

to :: Rep Inline x -> Inline #

Generic Lit 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Lit :: Type -> Type #

Methods

from :: Lit -> Rep Lit x #

to :: Rep Lit x -> Lit #

Generic Loc 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Loc :: Type -> Type #

Methods

from :: Loc -> Rep Loc x #

to :: Rep Loc x -> Loc #

Generic Match 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Match :: Type -> Type #

Methods

from :: Match -> Rep Match x #

to :: Rep Match x -> Match #

Generic ModName 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep ModName :: Type -> Type #

Methods

from :: ModName -> Rep ModName x #

to :: Rep ModName x -> ModName #

Generic Module 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Module :: Type -> Type #

Methods

from :: Module -> Rep Module x #

to :: Rep Module x -> Module #

Generic ModuleInfo 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep ModuleInfo :: Type -> Type #

Generic Name 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Name :: Type -> Type #

Methods

from :: Name -> Rep Name x #

to :: Rep Name x -> Name #

Generic NameFlavour 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep NameFlavour :: Type -> Type #

Generic NameSpace 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep NameSpace :: Type -> Type #

Generic OccName 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep OccName :: Type -> Type #

Methods

from :: OccName -> Rep OccName x #

to :: Rep OccName x -> OccName #

Generic Overlap 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Overlap :: Type -> Type #

Methods

from :: Overlap -> Rep Overlap x #

to :: Rep Overlap x -> Overlap #

Generic Pat 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Pat :: Type -> Type #

Methods

from :: Pat -> Rep Pat x #

to :: Rep Pat x -> Pat #

Generic PatSynArgs 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep PatSynArgs :: Type -> Type #

Generic PatSynDir 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep PatSynDir :: Type -> Type #

Generic Phases 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Phases :: Type -> Type #

Methods

from :: Phases -> Rep Phases x #

to :: Rep Phases x -> Phases #

Generic PkgName 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep PkgName :: Type -> Type #

Methods

from :: PkgName -> Rep PkgName x #

to :: Rep PkgName x -> PkgName #

Generic Pragma 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Pragma :: Type -> Type #

Methods

from :: Pragma -> Rep Pragma x #

to :: Rep Pragma x -> Pragma #

Generic Range 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Range :: Type -> Type #

Methods

from :: Range -> Rep Range x #

to :: Rep Range x -> Range #

Generic Role 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Role :: Type -> Type #

Methods

from :: Role -> Rep Role x #

to :: Rep Role x -> Role #

Generic RuleBndr 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep RuleBndr :: Type -> Type #

Methods

from :: RuleBndr -> Rep RuleBndr x #

to :: Rep RuleBndr x -> RuleBndr #

Generic RuleMatch 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep RuleMatch :: Type -> Type #

Generic Safety 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Safety :: Type -> Type #

Methods

from :: Safety -> Rep Safety x #

to :: Rep Safety x -> Safety #

Generic SourceStrictness 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep SourceStrictness :: Type -> Type #

Generic SourceUnpackedness 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep SourceUnpackedness :: Type -> Type #

Generic Specificity 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Specificity :: Type -> Type #

Generic Stmt 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Stmt :: Type -> Type #

Methods

from :: Stmt -> Rep Stmt x #

to :: Rep Stmt x -> Stmt #

Generic TyLit 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep TyLit :: Type -> Type #

Methods

from :: TyLit -> Rep TyLit x #

to :: Rep TyLit x -> TyLit #

Generic TySynEqn 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep TySynEqn :: Type -> Type #

Methods

from :: TySynEqn -> Rep TySynEqn x #

to :: Rep TySynEqn x -> TySynEqn #

Generic Type 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep Type :: Type -> Type #

Methods

from :: Type -> Rep Type x #

to :: Rep Type x -> Type #

Generic TypeFamilyHead 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep TypeFamilyHead :: Type -> Type #

Generic () 
Instance details

Defined in GHC.Generics

Associated Types

type Rep () :: Type -> Type #

Methods

from :: () -> Rep () x #

to :: Rep () x -> () #

Generic Bool 
Instance details

Defined in GHC.Generics

Associated Types

type Rep Bool :: Type -> Type #

Methods

from :: Bool -> Rep Bool x #

to :: Rep Bool x -> Bool #

Generic (ZipList a) 
Instance details

Defined in Control.Applicative

Associated Types

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

Methods

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

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

Generic (Complex a) 
Instance details

Defined in Data.Complex

Associated Types

type Rep (Complex a) :: Type -> Type #

Methods

from :: Complex a -> Rep (Complex a) x #

to :: Rep (Complex a) x -> Complex a #

Generic (Identity a) 
Instance details

Defined in Data.Functor.Identity

Associated Types

type Rep (Identity a) :: Type -> Type #

Methods

from :: Identity a -> Rep (Identity a) x #

to :: Rep (Identity a) x -> Identity a #

Generic (First a) 
Instance details

Defined in Data.Monoid

Associated Types

type Rep (First a) :: Type -> Type #

Methods

from :: First a -> Rep (First a) x #

to :: Rep (First a) x -> First a #

Generic (Last a) 
Instance details

Defined in Data.Monoid

Associated Types

type Rep (Last a) :: Type -> Type #

Methods

from :: Last a -> Rep (Last a) x #

to :: Rep (Last a) x -> Last a #

Generic (Down a) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (Down a) :: Type -> Type #

Methods

from :: Down a -> Rep (Down a) x #

to :: Rep (Down a) x -> Down a #

Generic (First a) 
Instance details

Defined in Data.Semigroup

Associated Types

type Rep (First a) :: Type -> Type #

Methods

from :: First a -> Rep (First a) x #

to :: Rep (First a) x -> First a #

Generic (Last a) 
Instance details

Defined in Data.Semigroup

Associated Types

type Rep (Last a) :: Type -> Type #

Methods

from :: Last a -> Rep (Last a) x #

to :: Rep (Last a) x -> Last a #

Generic (Max a) 
Instance details

Defined in Data.Semigroup

Associated Types

type Rep (Max a) :: Type -> Type #

Methods

from :: Max a -> Rep (Max a) x #

to :: Rep (Max a) x -> Max a #

Generic (Min a) 
Instance details

Defined in Data.Semigroup

Associated Types

type Rep (Min a) :: Type -> Type #

Methods

from :: Min a -> Rep (Min a) x #

to :: Rep (Min a) x -> Min a #

Generic (WrappedMonoid m) 
Instance details

Defined in Data.Semigroup

Associated Types

type Rep (WrappedMonoid m) :: Type -> Type #

Generic (Dual a) 
Instance details

Defined in Data.Semigroup.Internal

Associated Types

type Rep (Dual a) :: Type -> Type #

Methods

from :: Dual a -> Rep (Dual a) x #

to :: Rep (Dual a) x -> Dual a #

Generic (Endo a) 
Instance details

Defined in Data.Semigroup.Internal

Associated Types

type Rep (Endo a) :: Type -> Type #

Methods

from :: Endo a -> Rep (Endo a) x #

to :: Rep (Endo a) x -> Endo a #

Generic (Product a) 
Instance details

Defined in Data.Semigroup.Internal

Associated Types

type Rep (Product a) :: Type -> Type #

Methods

from :: Product a -> Rep (Product a) x #

to :: Rep (Product a) x -> Product a #

Generic (Sum a) 
Instance details

Defined in Data.Semigroup.Internal

Associated Types

type Rep (Sum a) :: Type -> Type #

Methods

from :: Sum a -> Rep (Sum a) x #

to :: Rep (Sum a) x -> Sum a #

Generic (Par1 p) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (Par1 p) :: Type -> Type #

Methods

from :: Par1 p -> Rep (Par1 p) x #

to :: Rep (Par1 p) x -> Par1 p #

Generic (SCC vertex) 
Instance details

Defined in Data.Graph

Associated Types

type Rep (SCC vertex) :: Type -> Type #

Methods

from :: SCC vertex -> Rep (SCC vertex) x #

to :: Rep (SCC vertex) x -> SCC vertex #

Generic (Digit a) 
Instance details

Defined in Data.Sequence.Internal

Associated Types

type Rep (Digit a) :: Type -> Type #

Methods

from :: Digit a -> Rep (Digit a) x #

to :: Rep (Digit a) x -> Digit a #

Generic (Elem a) 
Instance details

Defined in Data.Sequence.Internal

Associated Types

type Rep (Elem a) :: Type -> Type #

Methods

from :: Elem a -> Rep (Elem a) x #

to :: Rep (Elem a) x -> Elem a #

Generic (FingerTree a) 
Instance details

Defined in Data.Sequence.Internal

Associated Types

type Rep (FingerTree a) :: Type -> Type #

Methods

from :: FingerTree a -> Rep (FingerTree a) x #

to :: Rep (FingerTree a) x -> FingerTree a #

Generic (Node a) 
Instance details

Defined in Data.Sequence.Internal

Associated Types

type Rep (Node a) :: Type -> Type #

Methods

from :: Node a -> Rep (Node a) x #

to :: Rep (Node a) x -> Node a #

Generic (ViewL a) 
Instance details

Defined in Data.Sequence.Internal

Associated Types

type Rep (ViewL a) :: Type -> Type #

Methods

from :: ViewL a -> Rep (ViewL a) x #

to :: Rep (ViewL a) x -> ViewL a #

Generic (ViewR a) 
Instance details

Defined in Data.Sequence.Internal

Associated Types

type Rep (ViewR a) :: Type -> Type #

Methods

from :: ViewR a -> Rep (ViewR a) x #

to :: Rep (ViewR a) x -> ViewR a #

Generic (Tree a) 
Instance details

Defined in Data.Tree

Associated Types

type Rep (Tree a) :: Type -> Type #

Methods

from :: Tree a -> Rep (Tree a) x #

to :: Rep (Tree a) x -> Tree a #

Generic (SizedSeq a) 
Instance details

Defined in GHC.Data.SizedSeq

Associated Types

type Rep (SizedSeq a) :: Type -> Type #

Methods

from :: SizedSeq a -> Rep (SizedSeq a) x #

to :: Rep (SizedSeq a) x -> SizedSeq a #

Generic (GenClosure b) 
Instance details

Defined in GHC.Exts.Heap.Closures

Associated Types

type Rep (GenClosure b) :: Type -> Type #

Methods

from :: GenClosure b -> Rep (GenClosure b) x #

to :: Rep (GenClosure b) x -> GenClosure b #

Generic (EvalExpr a) 
Instance details

Defined in GHCi.Message

Associated Types

type Rep (EvalExpr a) :: Type -> Type #

Methods

from :: EvalExpr a -> Rep (EvalExpr a) x #

to :: Rep (EvalExpr a) x -> EvalExpr a #

Generic (EvalResult a) 
Instance details

Defined in GHCi.Message

Associated Types

type Rep (EvalResult a) :: Type -> Type #

Methods

from :: EvalResult a -> Rep (EvalResult a) x #

to :: Rep (EvalResult a) x -> EvalResult a #

Generic (QResult a) 
Instance details

Defined in GHCi.Message

Associated Types

type Rep (QResult a) :: Type -> Type #

Methods

from :: QResult a -> Rep (QResult a) x #

to :: Rep (QResult a) x -> QResult a #

Generic (THResult a) 
Instance details

Defined in GHCi.Message

Associated Types

type Rep (THResult a) :: Type -> Type #

Methods

from :: THResult a -> Rep (THResult a) x #

to :: Rep (THResult a) x -> THResult a #

Generic (Doc a) 
Instance details

Defined in Text.PrettyPrint.Annotated.HughesPJ

Associated Types

type Rep (Doc a) :: Type -> Type #

Methods

from :: Doc a -> Rep (Doc a) x #

to :: Rep (Doc a) x -> Doc a #

Generic (TyVarBndr flag) 
Instance details

Defined in Language.Haskell.TH.Syntax

Associated Types

type Rep (TyVarBndr flag) :: Type -> Type #

Methods

from :: TyVarBndr flag -> Rep (TyVarBndr flag) x #

to :: Rep (TyVarBndr flag) x -> TyVarBndr flag #

Generic (NonEmpty a) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (NonEmpty a) :: Type -> Type #

Methods

from :: NonEmpty a -> Rep (NonEmpty a) x #

to :: Rep (NonEmpty a) x -> NonEmpty a #

Generic (Maybe a) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (Maybe a) :: Type -> Type #

Methods

from :: Maybe a -> Rep (Maybe a) x #

to :: Rep (Maybe a) x -> Maybe a #

Generic (a) 
Instance details

Defined in GHC.Generics

Associated Types

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

Methods

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

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

Generic [a] 
Instance details

Defined in GHC.Generics

Associated Types

type Rep [a] :: Type -> Type #

Methods

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

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

Generic (WrappedMonad m a) 
Instance details

Defined in Control.Applicative

Associated Types

type Rep (WrappedMonad m a) :: Type -> Type #

Methods

from :: WrappedMonad m a -> Rep (WrappedMonad m a) x #

to :: Rep (WrappedMonad m a) x -> WrappedMonad m a #

Generic (Either a b) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (Either a b) :: Type -> Type #

Methods

from :: Either a b -> Rep (Either a b) x #

to :: Rep (Either a b) x -> Either a b #

Generic (Proxy t) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (Proxy t) :: Type -> Type #

Methods

from :: Proxy t -> Rep (Proxy t) x #

to :: Rep (Proxy t) x -> Proxy t #

Generic (Arg a b) 
Instance details

Defined in Data.Semigroup

Associated Types

type Rep (Arg a b) :: Type -> Type #

Methods

from :: Arg a b -> Rep (Arg a b) x #

to :: Rep (Arg a b) x -> Arg a b #

Generic (U1 p) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (U1 p) :: Type -> Type #

Methods

from :: U1 p -> Rep (U1 p) x #

to :: Rep (U1 p) x -> U1 p #

Generic (V1 p) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (V1 p) :: Type -> Type #

Methods

from :: V1 p -> Rep (V1 p) x #

to :: Rep (V1 p) x -> V1 p #

Generic (EvalStatus_ a b) 
Instance details

Defined in GHCi.Message

Associated Types

type Rep (EvalStatus_ a b) :: Type -> Type #

Methods

from :: EvalStatus_ a b -> Rep (EvalStatus_ a b) x #

to :: Rep (EvalStatus_ a b) x -> EvalStatus_ a b #

Generic (These a b) 
Instance details

Defined in Data.These

Associated Types

type Rep (These a b) :: Type -> Type #

Methods

from :: These a b -> Rep (These a b) x #

to :: Rep (These a b) x -> These a b #

Generic (Validation e a) 
Instance details

Defined in Validation

Associated Types

type Rep (Validation e a) :: Type -> Type #

Methods

from :: Validation e a -> Rep (Validation e a) x #

to :: Rep (Validation e a) x -> Validation e a #

Generic (a, b) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (a, b) :: Type -> Type #

Methods

from :: (a, b) -> Rep (a, b) x #

to :: Rep (a, b) x -> (a, b) #

Generic (WrappedArrow a b c) 
Instance details

Defined in Control.Applicative

Associated Types

type Rep (WrappedArrow a b c) :: Type -> Type #

Methods

from :: WrappedArrow a b c -> Rep (WrappedArrow a b c) x #

to :: Rep (WrappedArrow a b c) x -> WrappedArrow a b c #

Generic (Kleisli m a b) 
Instance details

Defined in Control.Arrow

Associated Types

type Rep (Kleisli m a b) :: Type -> Type #

Methods

from :: Kleisli m a b -> Rep (Kleisli m a b) x #

to :: Rep (Kleisli m a b) x -> Kleisli m a b #

Generic (Const a b) 
Instance details

Defined in Data.Functor.Const

Associated Types

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

Methods

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

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

Generic (Ap f a) 
Instance details

Defined in Data.Monoid

Associated Types

type Rep (Ap f a) :: Type -> Type #

Methods

from :: Ap f a -> Rep (Ap f a) x #

to :: Rep (Ap f a) x -> Ap f a #

Generic (Alt f a) 
Instance details

Defined in Data.Semigroup.Internal

Associated Types

type Rep (Alt f a) :: Type -> Type #

Methods

from :: Alt f a -> Rep (Alt f a) x #

to :: Rep (Alt f a) x -> Alt f a #

Generic (Rec1 f p) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (Rec1 f p) :: Type -> Type #

Methods

from :: Rec1 f p -> Rep (Rec1 f p) x #

to :: Rep (Rec1 f p) x -> Rec1 f p #

Generic (URec (Ptr ()) p) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (URec (Ptr ()) p) :: Type -> Type #

Methods

from :: URec (Ptr ()) p -> Rep (URec (Ptr ()) p) x #

to :: Rep (URec (Ptr ()) p) x -> URec (Ptr ()) p #

Generic (URec Char p) 
Instance details

Defined in GHC.Generics

Associated Types

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

Methods

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

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

Generic (URec Double p) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (URec Double p) :: Type -> Type #

Methods

from :: URec Double p -> Rep (URec Double p) x #

to :: Rep (URec Double p) x -> URec Double p #

Generic (URec Float p) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (URec Float p) :: Type -> Type #

Methods

from :: URec Float p -> Rep (URec Float p) x #

to :: Rep (URec Float p) x -> URec Float p #

Generic (URec Int p) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (URec Int p) :: Type -> Type #

Methods

from :: URec Int p -> Rep (URec Int p) x #

to :: Rep (URec Int p) x -> URec Int p #

Generic (URec Word p) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (URec Word p) :: Type -> Type #

Methods

from :: URec Word p -> Rep (URec Word p) x #

to :: Rep (URec Word p) x -> URec Word p #

Generic (Join p a) 
Instance details

Defined in Data.Bifunctor.Join

Associated Types

type Rep (Join p a) :: Type -> Type #

Methods

from :: Join p a -> Rep (Join p a) x #

to :: Rep (Join p a) x -> Join p a #

Generic (Tagged s b) 
Instance details

Defined in Data.Tagged

Associated Types

type Rep (Tagged s b) :: Type -> Type #

Methods

from :: Tagged s b -> Rep (Tagged s b) x #

to :: Rep (Tagged s b) x -> Tagged s b #

Generic (a, b, c) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (a, b, c) :: Type -> Type #

Methods

from :: (a, b, c) -> Rep (a, b, c) x #

to :: Rep (a, b, c) x -> (a, b, c) #

Generic (Product f g a) 
Instance details

Defined in Data.Functor.Product

Associated Types

type Rep (Product f g a) :: Type -> Type #

Methods

from :: Product f g a -> Rep (Product f g a) x #

to :: Rep (Product f g a) x -> Product f g a #

Generic (Sum f g a) 
Instance details

Defined in Data.Functor.Sum

Associated Types

type Rep (Sum f g a) :: Type -> Type #

Methods

from :: Sum f g a -> Rep (Sum f g a) x #

to :: Rep (Sum f g a) x -> Sum f g a #

Generic ((f :*: g) p) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep ((f :*: g) p) :: Type -> Type #

Methods

from :: (f :*: g) p -> Rep ((f :*: g) p) x #

to :: Rep ((f :*: g) p) x -> (f :*: g) p #

Generic ((f :+: g) p) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep ((f :+: g) p) :: Type -> Type #

Methods

from :: (f :+: g) p -> Rep ((f :+: g) p) x #

to :: Rep ((f :+: g) p) x -> (f :+: g) p #

Generic (K1 i c p) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (K1 i c p) :: Type -> Type #

Methods

from :: K1 i c p -> Rep (K1 i c p) x #

to :: Rep (K1 i c p) x -> K1 i c p #

Generic (a, b, c, d) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (a, b, c, d) :: Type -> Type #

Methods

from :: (a, b, c, d) -> Rep (a, b, c, d) x #

to :: Rep (a, b, c, d) x -> (a, b, c, d) #

Generic (Compose f g a) 
Instance details

Defined in Data.Functor.Compose

Associated Types

type Rep (Compose f g a) :: Type -> Type #

Methods

from :: Compose f g a -> Rep (Compose f g a) x #

to :: Rep (Compose f g a) x -> Compose f g a #

Generic ((f :.: g) p) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep ((f :.: g) p) :: Type -> Type #

Methods

from :: (f :.: g) p -> Rep ((f :.: g) p) x #

to :: Rep ((f :.: g) p) x -> (f :.: g) p #

Generic (M1 i c f p) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (M1 i c f p) :: Type -> Type #

Methods

from :: M1 i c f p -> Rep (M1 i c f p) x #

to :: Rep (M1 i c f p) x -> M1 i c f p #

Generic (Clown f a b) 
Instance details

Defined in Data.Bifunctor.Clown

Associated Types

type Rep (Clown f a b) :: Type -> Type #

Methods

from :: Clown f a b -> Rep (Clown f a b) x #

to :: Rep (Clown f a b) x -> Clown f a b #

Generic (Flip p a b) 
Instance details

Defined in Data.Bifunctor.Flip

Associated Types

type Rep (Flip p a b) :: Type -> Type #

Methods

from :: Flip p a b -> Rep (Flip p a b) x #

to :: Rep (Flip p a b) x -> Flip p a b #

Generic (Joker g a b) 
Instance details

Defined in Data.Bifunctor.Joker

Associated Types

type Rep (Joker g a b) :: Type -> Type #

Methods

from :: Joker g a b -> Rep (Joker g a b) x #

to :: Rep (Joker g a b) x -> Joker g a b #

Generic (WrappedBifunctor p a b) 
Instance details

Defined in Data.Bifunctor.Wrapped

Associated Types

type Rep (WrappedBifunctor p a b) :: Type -> Type #

Methods

from :: WrappedBifunctor p a b -> Rep (WrappedBifunctor p a b) x #

to :: Rep (WrappedBifunctor p a b) x -> WrappedBifunctor p a b #

Generic (a, b, c, d, e) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (a, b, c, d, e) :: Type -> Type #

Methods

from :: (a, b, c, d, e) -> Rep (a, b, c, d, e) x #

to :: Rep (a, b, c, d, e) x -> (a, b, c, d, e) #

Generic (Product f g a b) 
Instance details

Defined in Data.Bifunctor.Product

Associated Types

type Rep (Product f g a b) :: Type -> Type #

Methods

from :: Product f g a b -> Rep (Product f g a b) x #

to :: Rep (Product f g a b) x -> Product f g a b #

Generic (Sum p q a b) 
Instance details

Defined in Data.Bifunctor.Sum

Associated Types

type Rep (Sum p q a b) :: Type -> Type #

Methods

from :: Sum p q a b -> Rep (Sum p q a b) x #

to :: Rep (Sum p q a b) x -> Sum p q a b #

Generic (a, b, c, d, e, f) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (a, b, c, d, e, f) :: Type -> Type #

Methods

from :: (a, b, c, d, e, f) -> Rep (a, b, c, d, e, f) x #

to :: Rep (a, b, c, d, e, f) x -> (a, b, c, d, e, f) #

Generic (Tannen f p a b) 
Instance details

Defined in Data.Bifunctor.Tannen

Associated Types

type Rep (Tannen f p a b) :: Type -> Type #

Methods

from :: Tannen f p a b -> Rep (Tannen f p a b) x #

to :: Rep (Tannen f p a b) x -> Tannen f p a b #

Generic (a, b, c, d, e, f, g) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (a, b, c, d, e, f, g) :: Type -> Type #

Methods

from :: (a, b, c, d, e, f, g) -> Rep (a, b, c, d, e, f, g) x #

to :: Rep (a, b, c, d, e, f, g) x -> (a, b, c, d, e, f, g) #

Generic (a, b, c, d, e, f, g, h) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (a, b, c, d, e, f, g, h) :: Type -> Type #

Methods

from :: (a, b, c, d, e, f, g, h) -> Rep (a, b, c, d, e, f, g, h) x #

to :: Rep (a, b, c, d, e, f, g, h) x -> (a, b, c, d, e, f, g, h) #

Generic (Biff p f g a b) 
Instance details

Defined in Data.Bifunctor.Biff

Associated Types

type Rep (Biff p f g a b) :: Type -> Type #

Methods

from :: Biff p f g a b -> Rep (Biff p f g a b) x #

to :: Rep (Biff p f g a b) x -> Biff p f g a b #

Generic (a, b, c, d, e, f, g, h, i) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (a, b, c, d, e, f, g, h, i) :: Type -> Type #

Methods

from :: (a, b, c, d, e, f, g, h, i) -> Rep (a, b, c, d, e, f, g, h, i) x #

to :: Rep (a, b, c, d, e, f, g, h, i) x -> (a, b, c, d, e, f, g, h, i) #

Generic (a, b, c, d, e, f, g, h, i, j) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (a, b, c, d, e, f, g, h, i, j) :: Type -> Type #

Methods

from :: (a, b, c, d, e, f, g, h, i, j) -> Rep (a, b, c, d, e, f, g, h, i, j) x #

to :: Rep (a, b, c, d, e, f, g, h, i, j) x -> (a, b, c, d, e, f, g, h, i, j) #

Generic (a, b, c, d, e, f, g, h, i, j, k) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (a, b, c, d, e, f, g, h, i, j, k) :: Type -> Type #

Methods

from :: (a, b, c, d, e, f, g, h, i, j, k) -> Rep (a, b, c, d, e, f, g, h, i, j, k) x #

to :: Rep (a, b, c, d, e, f, g, h, i, j, k) x -> (a, b, c, d, e, f, g, h, i, j, k) #

Generic (a, b, c, d, e, f, g, h, i, j, k, l) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (a, b, c, d, e, f, g, h, i, j, k, l) :: Type -> Type #

Methods

from :: (a, b, c, d, e, f, g, h, i, j, k, l) -> Rep (a, b, c, d, e, f, g, h, i, j, k, l) x #

to :: Rep (a, b, c, d, e, f, g, h, i, j, k, l) x -> (a, b, c, d, e, f, g, h, i, j, k, l) #

Generic (a, b, c, d, e, f, g, h, i, j, k, l, m) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (a, b, c, d, e, f, g, h, i, j, k, l, m) :: Type -> Type #

Methods

from :: (a, b, c, d, e, f, g, h, i, j, k, l, m) -> Rep (a, b, c, d, e, f, g, h, i, j, k, l, m) x #

to :: Rep (a, b, c, d, e, f, g, h, i, j, k, l, m) x -> (a, b, c, d, e, f, g, h, i, j, k, l, m) #

Generic (a, b, c, d, e, f, g, h, i, j, k, l, m, n) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (a, b, c, d, e, f, g, h, i, j, k, l, m, n) :: Type -> Type #

Methods

from :: (a, b, c, d, e, f, g, h, i, j, k, l, m, n) -> Rep (a, b, c, d, e, f, g, h, i, j, k, l, m, n) x #

to :: Rep (a, b, c, d, e, f, g, h, i, j, k, l, m, n) x -> (a, b, c, d, e, f, g, h, i, j, k, l, m, n) #

Generic (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) :: Type -> Type #

Methods

from :: (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) -> Rep (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) x #

to :: Rep (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) x -> (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) #

class Semigroup a #

The class of semigroups (types with an associative binary operation).

Instances should satisfy the following:

Associativity
x <> (y <> z) = (x <> y) <> z

Since: base-4.9.0.0

Minimal complete definition

(<>)

Instances

Instances details
Semigroup All

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup.Internal

Methods

(<>) :: All -> All -> All #

sconcat :: NonEmpty All -> All #

stimes :: Integral b => b -> All -> All #

Semigroup Any

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup.Internal

Methods

(<>) :: Any -> Any -> Any #

sconcat :: NonEmpty Any -> Any #

stimes :: Integral b => b -> Any -> Any #

Semigroup Void

Since: base-4.9.0.0

Instance details

Defined in Data.Void

Methods

(<>) :: Void -> Void -> Void #

sconcat :: NonEmpty Void -> Void #

stimes :: Integral b => b -> Void -> Void #

Semigroup Builder 
Instance details

Defined in Data.ByteString.Builder.Internal

Semigroup ByteString 
Instance details

Defined in Data.ByteString.Internal

Semigroup ByteString 
Instance details

Defined in Data.ByteString.Lazy.Internal

Semigroup ShortByteString 
Instance details

Defined in Data.ByteString.Short.Internal

Semigroup IntSet

Since: containers-0.5.7

Instance details

Defined in Data.IntSet.Internal

Semigroup ByteArray 
Instance details

Defined in Data.Array.Byte

Semigroup UniqueSet 
Instance details

Defined in GHC.Cmm.Dataflow.Collections

Semigroup LabelSet 
Instance details

Defined in GHC.Cmm.Dataflow.Label

Semigroup Ordering

Since: base-4.9.0.0

Instance details

Defined in GHC.Base

Semigroup Doc 
Instance details

Defined in Text.PrettyPrint.HughesPJ

Methods

(<>) :: Doc -> Doc -> Doc #

sconcat :: NonEmpty Doc -> Doc #

stimes :: Integral b => b -> Doc -> Doc #

Semigroup ()

Since: base-4.9.0.0

Instance details

Defined in GHC.Base

Methods

(<>) :: () -> () -> () #

sconcat :: NonEmpty () -> () #

stimes :: Integral b => b -> () -> () #

Semigroup (Comparison a)

(<>) on comparisons combines results with (<>) @Ordering. Without newtypes this equals liftA2 (liftA2 (<>)).

(<>) :: Comparison a -> Comparison a -> Comparison a
Comparison cmp <> Comparison cmp' = Comparison a a' ->
  cmp a a' <> cmp a a'
Instance details

Defined in Data.Functor.Contravariant

Semigroup (Equivalence a)

(<>) on equivalences uses logical conjunction (&&) on the results. Without newtypes this equals liftA2 (liftA2 (&&)).

(<>) :: Equivalence a -> Equivalence a -> Equivalence a
Equivalence equiv <> Equivalence equiv' = Equivalence a b ->
  equiv a b && equiv a b
Instance details

Defined in Data.Functor.Contravariant

Semigroup (Predicate a)

(<>) on predicates uses logical conjunction (&&) on the results. Without newtypes this equals liftA2 (&&).

(<>) :: Predicate a -> Predicate a -> Predicate a
Predicate pred <> Predicate pred' = Predicate a ->
  pred a && pred' a
Instance details

Defined in Data.Functor.Contravariant

Methods

(<>) :: Predicate a -> Predicate a -> Predicate a #

sconcat :: NonEmpty (Predicate a) -> Predicate a #

stimes :: Integral b => b -> Predicate a -> Predicate a #

Semigroup a => Semigroup (Identity a)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Identity

Methods

(<>) :: Identity a -> Identity a -> Identity a #

sconcat :: NonEmpty (Identity a) -> Identity a #

stimes :: Integral b => b -> Identity a -> Identity a #

Semigroup (First a)

Since: base-4.9.0.0

Instance details

Defined in Data.Monoid

Methods

(<>) :: First a -> First a -> First a #

sconcat :: NonEmpty (First a) -> First a #

stimes :: Integral b => b -> First a -> First a #

Semigroup (Last a)

Since: base-4.9.0.0

Instance details

Defined in Data.Monoid

Methods

(<>) :: Last a -> Last a -> Last a #

sconcat :: NonEmpty (Last a) -> Last a #

stimes :: Integral b => b -> Last a -> Last a #

Semigroup a => Semigroup (Down a)

Since: base-4.11.0.0

Instance details

Defined in Data.Ord

Methods

(<>) :: Down a -> Down a -> Down a #

sconcat :: NonEmpty (Down a) -> Down a #

stimes :: Integral b => b -> Down a -> Down a #

Semigroup (First a)

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Methods

(<>) :: First a -> First a -> First a #

sconcat :: NonEmpty (First a) -> First a #

stimes :: Integral b => b -> First a -> First a #

Semigroup (Last a)

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Methods

(<>) :: Last a -> Last a -> Last a #

sconcat :: NonEmpty (Last a) -> Last a #

stimes :: Integral b => b -> Last a -> Last a #

Ord a => Semigroup (Max a)

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Methods

(<>) :: Max a -> Max a -> Max a #

sconcat :: NonEmpty (Max a) -> Max a #

stimes :: Integral b => b -> Max a -> Max a #

Ord a => Semigroup (Min a)

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Methods

(<>) :: Min a -> Min a -> Min a #

sconcat :: NonEmpty (Min a) -> Min a #

stimes :: Integral b => b -> Min a -> Min a #

Monoid m => Semigroup (WrappedMonoid m)

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Semigroup a => Semigroup (Dual a)

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup.Internal

Methods

(<>) :: Dual a -> Dual a -> Dual a #

sconcat :: NonEmpty (Dual a) -> Dual a #

stimes :: Integral b => b -> Dual a -> Dual a #

Semigroup (Endo a)

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup.Internal

Methods

(<>) :: Endo a -> Endo a -> Endo a #

sconcat :: NonEmpty (Endo a) -> Endo a #

stimes :: Integral b => b -> Endo a -> Endo a #

Num a => Semigroup (Product a)

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup.Internal

Methods

(<>) :: Product a -> Product a -> Product a #

sconcat :: NonEmpty (Product a) -> Product a #

stimes :: Integral b => b -> Product a -> Product a #

Num a => Semigroup (Sum a)

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup.Internal

Methods

(<>) :: Sum a -> Sum a -> Sum a #

sconcat :: NonEmpty (Sum a) -> Sum a #

stimes :: Integral b => b -> Sum a -> Sum a #

Semigroup p => Semigroup (Par1 p)

Since: base-4.12.0.0

Instance details

Defined in GHC.Generics

Methods

(<>) :: Par1 p -> Par1 p -> Par1 p #

sconcat :: NonEmpty (Par1 p) -> Par1 p #

stimes :: Integral b => b -> Par1 p -> Par1 p #

Semigroup (IntMap a)

Since: containers-0.5.7

Instance details

Defined in Data.IntMap.Internal

Methods

(<>) :: IntMap a -> IntMap a -> IntMap a #

sconcat :: NonEmpty (IntMap a) -> IntMap a #

stimes :: Integral b => b -> IntMap a -> IntMap a #

Semigroup (Seq a)

Since: containers-0.5.7

Instance details

Defined in Data.Sequence.Internal

Methods

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

sconcat :: NonEmpty (Seq a) -> Seq a #

stimes :: Integral b => b -> Seq a -> Seq a #

Semigroup (MergeSet a) 
Instance details

Defined in Data.Set.Internal

Methods

(<>) :: MergeSet a -> MergeSet a -> MergeSet a #

sconcat :: NonEmpty (MergeSet a) -> MergeSet a #

stimes :: Integral b => b -> MergeSet a -> MergeSet a #

Ord a => Semigroup (Set a)

Since: containers-0.5.7

Instance details

Defined in Data.Set.Internal

Methods

(<>) :: Set a -> Set a -> Set a #

sconcat :: NonEmpty (Set a) -> Set a #

stimes :: Integral b => b -> Set a -> Set a #

Semigroup (FromMaybe b) 
Instance details

Defined in Data.Foldable1

Methods

(<>) :: FromMaybe b -> FromMaybe b -> FromMaybe b #

sconcat :: NonEmpty (FromMaybe b) -> FromMaybe b #

stimes :: Integral b0 => b0 -> FromMaybe b -> FromMaybe b #

Semigroup a => Semigroup (JoinWith a) 
Instance details

Defined in Data.Foldable1

Methods

(<>) :: JoinWith a -> JoinWith a -> JoinWith a #

sconcat :: NonEmpty (JoinWith a) -> JoinWith a #

stimes :: Integral b => b -> JoinWith a -> JoinWith a #

Semigroup (NonEmptyDList a) 
Instance details

Defined in Data.Foldable1

Methods

(<>) :: NonEmptyDList a -> NonEmptyDList a -> NonEmptyDList a #

sconcat :: NonEmpty (NonEmptyDList a) -> NonEmptyDList a #

stimes :: Integral b => b -> NonEmptyDList a -> NonEmptyDList a #

Semigroup a => Semigroup (IO a)

Since: base-4.10.0.0

Instance details

Defined in GHC.Base

Methods

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

sconcat :: NonEmpty (IO a) -> IO a #

stimes :: Integral b => b -> IO a -> IO a #

Semigroup (Doc a) 
Instance details

Defined in Text.PrettyPrint.Annotated.HughesPJ

Methods

(<>) :: Doc a -> Doc a -> Doc a #

sconcat :: NonEmpty (Doc a) -> Doc a #

stimes :: Integral b => b -> Doc a -> Doc a #

Semigroup a => Semigroup (JoinWith a) 
Instance details

Defined in Data.Semigroup.Foldable

Methods

(<>) :: JoinWith a -> JoinWith a -> JoinWith a #

sconcat :: NonEmpty (JoinWith a) -> JoinWith a #

stimes :: Integral b => b -> JoinWith a -> JoinWith a #

Semigroup a => Semigroup (Q a)

Since: template-haskell-2.17.0.0

Instance details

Defined in Language.Haskell.TH.Syntax

Methods

(<>) :: Q a -> Q a -> Q a #

sconcat :: NonEmpty (Q a) -> Q a #

stimes :: Integral b => b -> Q a -> Q a #

(Hashable a, Eq a) => Semigroup (HashSet a)

<> = union

\(O(n+m)\)

To obtain good performance, the smaller set must be presented as the first argument.

Examples

Expand
>>> fromList [1,2] <> fromList [2,3]
fromList [1,2,3]
Instance details

Defined in Data.HashSet.Internal

Methods

(<>) :: HashSet a -> HashSet a -> HashSet a #

sconcat :: NonEmpty (HashSet a) -> HashSet a #

stimes :: Integral b => b -> HashSet a -> HashSet a #

Semigroup (NonEmpty a)

Since: base-4.9.0.0

Instance details

Defined in GHC.Base

Methods

(<>) :: NonEmpty a -> NonEmpty a -> NonEmpty a #

sconcat :: NonEmpty (NonEmpty a) -> NonEmpty a #

stimes :: Integral b => b -> NonEmpty a -> NonEmpty a #

Semigroup a => Semigroup (Maybe a)

Since: base-4.9.0.0

Instance details

Defined in GHC.Base

Methods

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

sconcat :: NonEmpty (Maybe a) -> Maybe a #

stimes :: Integral b => b -> Maybe a -> Maybe a #

Semigroup a => Semigroup (a)

Since: base-4.15

Instance details

Defined in GHC.Base

Methods

(<>) :: (a) -> (a) -> (a) #

sconcat :: NonEmpty (a) -> (a) #

stimes :: Integral b => b -> (a) -> (a) #

Semigroup [a]

Since: base-4.9.0.0

Instance details

Defined in GHC.Base

Methods

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

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

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

Semigroup (Either a b)

Since: base-4.9.0.0

Instance details

Defined in Data.Either

Methods

(<>) :: Either a b -> Either a b -> Either a b #

sconcat :: NonEmpty (Either a b) -> Either a b #

stimes :: Integral b0 => b0 -> Either a b -> Either a b #

Semigroup a => Semigroup (Op a b)

(<>) @(Op a b) without newtypes is (<>) @(b->a) = liftA2 (<>). This lifts the Semigroup operation (<>) over the output of a.

(<>) :: Op a b -> Op a b -> Op a b
Op f <> Op g = Op a -> f a <> g a
Instance details

Defined in Data.Functor.Contravariant

Methods

(<>) :: Op a b -> Op a b -> Op a b #

sconcat :: NonEmpty (Op a b) -> Op a b #

stimes :: Integral b0 => b0 -> Op a b -> Op a b #

Semigroup (Proxy s)

Since: base-4.9.0.0

Instance details

Defined in Data.Proxy

Methods

(<>) :: Proxy s -> Proxy s -> Proxy s #

sconcat :: NonEmpty (Proxy s) -> Proxy s #

stimes :: Integral b => b -> Proxy s -> Proxy s #

Semigroup (U1 p)

Since: base-4.12.0.0

Instance details

Defined in GHC.Generics

Methods

(<>) :: U1 p -> U1 p -> U1 p #

sconcat :: NonEmpty (U1 p) -> U1 p #

stimes :: Integral b => b -> U1 p -> U1 p #

Semigroup (V1 p)

Since: base-4.12.0.0

Instance details

Defined in GHC.Generics

Methods

(<>) :: V1 p -> V1 p -> V1 p #

sconcat :: NonEmpty (V1 p) -> V1 p #

stimes :: Integral b => b -> V1 p -> V1 p #

Ord k => Semigroup (Map k v) 
Instance details

Defined in Data.Map.Internal

Methods

(<>) :: Map k v -> Map k v -> Map k v #

sconcat :: NonEmpty (Map k v) -> Map k v #

stimes :: Integral b => b -> Map k v -> Map k v #

Apply f => Semigroup (Act f a) 
Instance details

Defined in Data.Semigroup.Foldable

Methods

(<>) :: Act f a -> Act f a -> Act f a #

sconcat :: NonEmpty (Act f a) -> Act f a #

stimes :: Integral b => b -> Act f a -> Act f a #

Alt f => Semigroup (Alt_ f a) 
Instance details

Defined in Data.Semigroup.Foldable

Methods

(<>) :: Alt_ f a -> Alt_ f a -> Alt_ f a #

sconcat :: NonEmpty (Alt_ f a) -> Alt_ f a #

stimes :: Integral b => b -> Alt_ f a -> Alt_ f a #

(Semigroup a, Semigroup b) => Semigroup (These a b) 
Instance details

Defined in Data.These

Methods

(<>) :: These a b -> These a b -> These a b #

sconcat :: NonEmpty (These a b) -> These a b #

stimes :: Integral b0 => b0 -> These a b -> These a b #

(Eq k, Hashable k) => Semigroup (HashMap k v)

<> = union

If a key occurs in both maps, the mapping from the first will be the mapping in the result.

Examples

Expand
>>> fromList [(1,'a'),(2,'b')] <> fromList [(2,'c'),(3,'d')]
fromList [(1,'a'),(2,'b'),(3,'d')]
Instance details

Defined in Data.HashMap.Internal

Methods

(<>) :: HashMap k v -> HashMap k v -> HashMap k v #

sconcat :: NonEmpty (HashMap k v) -> HashMap k v #

stimes :: Integral b => b -> HashMap k v -> HashMap k v #

(Semigroup e, Semigroup a) => Semigroup (Validation e a)

Semigroup allows merging multiple Validations into single one by combining values inside both Failure and Success. The <> operator merges two Validations following the below rules:

  1. If both values are Failures, returns a new Failure with accumulated errors.
  2. If both values are Successful, returns a new Success with combined success using Semigroup for values inside Success.
  3. If one value is Failure and another one is Success, then Failure is returned.

Examples

>>> success1 = Success [9] :: Validation [String] [Int]
>>> success2 = Success [15] :: Validation [String] [Int]
>>> failure1 = Failure ["WRONG"] :: Validation [String] [Int]
>>> failure2 = Failure ["FAIL"]  :: Validation [String] [Int]
>>> success1 <> success2
Success [9,15]
>>> failure1 <> failure2
Failure ["WRONG","FAIL"]
>>> success1 <> failure1
Failure ["WRONG"]
>>> failure2 <> success1 <> success2 <> failure1
Failure ["FAIL","WRONG"]
Instance details

Defined in Validation

Methods

(<>) :: Validation e a -> Validation e a -> Validation e a #

sconcat :: NonEmpty (Validation e a) -> Validation e a #

stimes :: Integral b => b -> Validation e a -> Validation e a #

Semigroup b => Semigroup (a -> b)

Since: base-4.9.0.0

Instance details

Defined in GHC.Base

Methods

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

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

stimes :: Integral b0 => b0 -> (a -> b) -> a -> b #

(Semigroup a, Semigroup b) => Semigroup (a, b)

Since: base-4.9.0.0

Instance details

Defined in GHC.Base

Methods

(<>) :: (a, b) -> (a, b) -> (a, b) #

sconcat :: NonEmpty (a, b) -> (a, b) #

stimes :: Integral b0 => b0 -> (a, b) -> (a, b) #

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 #

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

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

(Applicative f, Semigroup a) => Semigroup (Ap f a)

Since: base-4.12.0.0

Instance details

Defined in Data.Monoid

Methods

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

sconcat :: NonEmpty (Ap f a) -> Ap f a #

stimes :: Integral b => b -> Ap f a -> Ap f a #

Alternative f => Semigroup (Alt f a)

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup.Internal

Methods

(<>) :: Alt f a -> Alt f a -> Alt f a #

sconcat :: NonEmpty (Alt f a) -> Alt f a #

stimes :: Integral b => b -> Alt f a -> Alt f a #

Semigroup (f p) => Semigroup (Rec1 f p)

Since: base-4.12.0.0

Instance details

Defined in GHC.Generics

Methods

(<>) :: Rec1 f p -> Rec1 f p -> Rec1 f p #

sconcat :: NonEmpty (Rec1 f p) -> Rec1 f p #

stimes :: Integral b => b -> Rec1 f p -> Rec1 f p #

Semigroup a => Semigroup (Tagged s a) 
Instance details

Defined in Data.Tagged

Methods

(<>) :: Tagged s a -> Tagged s a -> Tagged s a #

sconcat :: NonEmpty (Tagged s a) -> Tagged s a #

stimes :: Integral b => b -> Tagged s a -> Tagged s a #

(Semigroup a, Semigroup b, Semigroup c) => Semigroup (a, b, c)

Since: base-4.9.0.0

Instance details

Defined in GHC.Base

Methods

(<>) :: (a, b, c) -> (a, b, c) -> (a, b, c) #

sconcat :: NonEmpty (a, b, c) -> (a, b, c) #

stimes :: Integral b0 => b0 -> (a, b, c) -> (a, b, c) #

(Semigroup (f a), Semigroup (g a)) => Semigroup (Product f g a)

Since: base-4.16.0.0

Instance details

Defined in Data.Functor.Product

Methods

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

sconcat :: NonEmpty (Product f g a) -> Product f g a #

stimes :: Integral b => b -> Product f g a -> Product f g a #

(Semigroup (f p), Semigroup (g p)) => Semigroup ((f :*: g) p)

Since: base-4.12.0.0

Instance details

Defined in GHC.Generics

Methods

(<>) :: (f :*: g) p -> (f :*: g) p -> (f :*: g) p #

sconcat :: NonEmpty ((f :*: g) p) -> (f :*: g) p #

stimes :: Integral b => b -> (f :*: g) p -> (f :*: g) p #

Semigroup c => Semigroup (K1 i c p)

Since: base-4.12.0.0

Instance details

Defined in GHC.Generics

Methods

(<>) :: K1 i c p -> K1 i c p -> K1 i c p #

sconcat :: NonEmpty (K1 i c p) -> K1 i c p #

stimes :: Integral b => b -> K1 i c p -> K1 i c p #

(Semigroup a, Semigroup b, Semigroup c, Semigroup d) => Semigroup (a, b, c, d)

Since: base-4.9.0.0

Instance details

Defined in GHC.Base

Methods

(<>) :: (a, b, c, d) -> (a, b, c, d) -> (a, b, c, d) #

sconcat :: NonEmpty (a, b, c, d) -> (a, b, c, d) #

stimes :: Integral b0 => b0 -> (a, b, c, d) -> (a, b, c, d) #

Semigroup (f (g a)) => Semigroup (Compose f g a)

Since: base-4.16.0.0

Instance details

Defined in Data.Functor.Compose

Methods

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

sconcat :: NonEmpty (Compose f g a) -> Compose f g a #

stimes :: Integral b => b -> Compose f g a -> Compose f g a #

Semigroup (f (g p)) => Semigroup ((f :.: g) p)

Since: base-4.12.0.0

Instance details

Defined in GHC.Generics

Methods

(<>) :: (f :.: g) p -> (f :.: g) p -> (f :.: g) p #

sconcat :: NonEmpty ((f :.: g) p) -> (f :.: g) p #

stimes :: Integral b => b -> (f :.: g) p -> (f :.: g) p #

Semigroup (f p) => Semigroup (M1 i c f p)

Since: base-4.12.0.0

Instance details

Defined in GHC.Generics

Methods

(<>) :: M1 i c f p -> M1 i c f p -> M1 i c f p #

sconcat :: NonEmpty (M1 i c f p) -> M1 i c f p #

stimes :: Integral b => b -> M1 i c f p -> M1 i c f p #

(Semigroup a, Semigroup b, Semigroup c, Semigroup d, Semigroup e) => Semigroup (a, b, c, d, e)

Since: base-4.9.0.0

Instance details

Defined in GHC.Base

Methods

(<>) :: (a, b, c, d, e) -> (a, b, c, d, e) -> (a, b, c, d, e) #

sconcat :: NonEmpty (a, b, c, d, e) -> (a, b, c, d, e) #

stimes :: Integral b0 => b0 -> (a, b, c, d, e) -> (a, b, c, d, e) #

sconcat :: Semigroup a => NonEmpty a -> a #

Reduce a non-empty list with <>

The default definition should be sufficient, but this can be overridden for efficiency.

>>> import Data.List.NonEmpty (NonEmpty (..))
>>> sconcat $ "Hello" :| [" ", "Haskell", "!"]
"Hello Haskell!"

class Semigroup a => Monoid a #

The class of monoids (types with an associative binary operation that has an identity). Instances should satisfy the following:

Right identity
x <> mempty = x
Left identity
mempty <> x = x
Associativity
x <> (y <> z) = (x <> y) <> z (Semigroup law)
Concatenation
mconcat = foldr (<>) mempty

The method names refer to the monoid of lists under concatenation, but there are many other instances.

Some types can be viewed as a monoid in more than one way, e.g. both addition and multiplication on numbers. In such cases we often define newtypes and make those instances of Monoid, e.g. Sum and Product.

NOTE: Semigroup is a superclass of Monoid since base-4.11.0.0.

Minimal complete definition

mempty

Instances

Instances details
Monoid All

Since: base-2.1

Instance details

Defined in Data.Semigroup.Internal

Methods

mempty :: All #

mappend :: All -> All -> All #

mconcat :: [All] -> All #

Monoid Any

Since: base-2.1

Instance details

Defined in Data.Semigroup.Internal

Methods

mempty :: Any #

mappend :: Any -> Any -> Any #

mconcat :: [Any] -> Any #

Monoid Builder 
Instance details

Defined in Data.ByteString.Builder.Internal

Monoid ByteString 
Instance details

Defined in Data.ByteString.Internal

Monoid ByteString 
Instance details

Defined in Data.ByteString.Lazy.Internal

Monoid ShortByteString 
Instance details

Defined in Data.ByteString.Short.Internal

Monoid IntSet 
Instance details

Defined in Data.IntSet.Internal

Monoid ByteArray 
Instance details

Defined in Data.Array.Byte

Monoid UniqueSet 
Instance details

Defined in GHC.Cmm.Dataflow.Collections

Monoid LabelSet 
Instance details

Defined in GHC.Cmm.Dataflow.Label

Monoid Ordering

Since: base-2.1

Instance details

Defined in GHC.Base

Monoid Doc 
Instance details

Defined in Text.PrettyPrint.HughesPJ

Methods

mempty :: Doc #

mappend :: Doc -> Doc -> Doc #

mconcat :: [Doc] -> Doc #

Monoid ()

Since: base-2.1

Instance details

Defined in GHC.Base

Methods

mempty :: () #

mappend :: () -> () -> () #

mconcat :: [()] -> () #

Monoid (Comparison a)

mempty on comparisons always returns EQ. Without newtypes this equals pure (pure EQ).

mempty :: Comparison a
mempty = Comparison _ _ -> EQ
Instance details

Defined in Data.Functor.Contravariant

Monoid (Equivalence a)

mempty on equivalences always returns True. Without newtypes this equals pure (pure True).

mempty :: Equivalence a
mempty = Equivalence _ _ -> True
Instance details

Defined in Data.Functor.Contravariant

Monoid (Predicate a)

mempty on predicates always returns True. Without newtypes this equals pure True.

mempty :: Predicate a
mempty = _ -> True
Instance details

Defined in Data.Functor.Contravariant

Monoid a => Monoid (Identity a)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Identity

Methods

mempty :: Identity a #

mappend :: Identity a -> Identity a -> Identity a #

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

Monoid (First a)

Since: base-2.1

Instance details

Defined in Data.Monoid

Methods

mempty :: First a #

mappend :: First a -> First a -> First a #

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

Monoid (Last a)

Since: base-2.1

Instance details

Defined in Data.Monoid

Methods

mempty :: Last a #

mappend :: Last a -> Last a -> Last a #

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

Monoid a => Monoid (Down a)

Since: base-4.11.0.0

Instance details

Defined in Data.Ord

Methods

mempty :: Down a #

mappend :: Down a -> Down a -> Down a #

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

(Ord a, Bounded a) => Monoid (Max a)

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Methods

mempty :: Max a #

mappend :: Max a -> Max a -> Max a #

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

(Ord a, Bounded a) => Monoid (Min a)

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Methods

mempty :: Min a #

mappend :: Min a -> Min a -> Min a #

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

Monoid m => Monoid (WrappedMonoid m)

Since: base-4.9.0.0

Instance details

Defined in Data.Semigroup

Monoid a => Monoid (Dual a)

Since: base-2.1

Instance details

Defined in Data.Semigroup.Internal

Methods

mempty :: Dual a #

mappend :: Dual a -> Dual a -> Dual a #

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

Monoid (Endo a)

Since: base-2.1

Instance details

Defined in Data.Semigroup.Internal

Methods

mempty :: Endo a #

mappend :: Endo a -> Endo a -> Endo a #

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

Num a => Monoid (Product a)

Since: base-2.1

Instance details

Defined in Data.Semigroup.Internal

Methods

mempty :: Product a #

mappend :: Product a -> Product a -> Product a #

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

Num a => Monoid (Sum a)

Since: base-2.1

Instance details

Defined in Data.Semigroup.Internal

Methods

mempty :: Sum a #

mappend :: Sum a -> Sum a -> Sum a #

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

Monoid p => Monoid (Par1 p)

Since: base-4.12.0.0

Instance details

Defined in GHC.Generics

Methods

mempty :: Par1 p #

mappend :: Par1 p -> Par1 p -> Par1 p #

mconcat :: [Par1 p] -> Par1 p #

Monoid (IntMap a) 
Instance details

Defined in Data.IntMap.Internal

Methods

mempty :: IntMap a #

mappend :: IntMap a -> IntMap a -> IntMap a #

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

Monoid (Seq a) 
Instance details

Defined in Data.Sequence.Internal

Methods

mempty :: Seq a #

mappend :: Seq a -> Seq a -> Seq a #

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

Monoid (MergeSet a) 
Instance details

Defined in Data.Set.Internal

Methods

mempty :: MergeSet a #

mappend :: MergeSet a -> MergeSet a -> MergeSet a #

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

Ord a => Monoid (Set a) 
Instance details

Defined in Data.Set.Internal

Methods

mempty :: Set a #

mappend :: Set a -> Set a -> Set a #

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

Monoid a => Monoid (IO a)

Since: base-4.9.0.0

Instance details

Defined in GHC.Base

Methods

mempty :: IO a #

mappend :: IO a -> IO a -> IO a #

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

Monoid (Doc a) 
Instance details

Defined in Text.PrettyPrint.Annotated.HughesPJ

Methods

mempty :: Doc a #

mappend :: Doc a -> Doc a -> Doc a #

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

Monoid a => Monoid (Q a)

Since: template-haskell-2.17.0.0

Instance details

Defined in Language.Haskell.TH.Syntax

Methods

mempty :: Q a #

mappend :: Q a -> Q a -> Q a #

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

(Hashable a, Eq a) => Monoid (HashSet a)

mempty = empty

mappend = union

\(O(n+m)\)

To obtain good performance, the smaller set must be presented as the first argument.

Examples

Expand
>>> mappend (fromList [1,2]) (fromList [2,3])
fromList [1,2,3]
Instance details

Defined in Data.HashSet.Internal

Methods

mempty :: HashSet a #

mappend :: HashSet a -> HashSet a -> HashSet a #

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

Semigroup a => Monoid (Maybe a)

Lift a semigroup into Maybe forming a Monoid according to http://en.wikipedia.org/wiki/Monoid: "Any semigroup S may be turned into a monoid simply by adjoining an element e not in S and defining e*e = e and e*s = s = s*e for all s ∈ S."

Since 4.11.0: constraint on inner a value generalised from Monoid to Semigroup.

Since: base-2.1

Instance details

Defined in GHC.Base

Methods

mempty :: Maybe a #

mappend :: Maybe a -> Maybe a -> Maybe a #

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

Monoid a => Monoid (a)

Since: base-4.15

Instance details

Defined in GHC.Base

Methods

mempty :: (a) #

mappend :: (a) -> (a) -> (a) #

mconcat :: [(a)] -> (a) #

Monoid [a]

Since: base-2.1

Instance details

Defined in GHC.Base

Methods

mempty :: [a] #

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

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

Monoid a => Monoid (Op a b)

mempty @(Op a b) without newtypes is mempty @(b->a) = _ -> mempty.

mempty :: Op a b
mempty = Op _ -> mempty
Instance details

Defined in Data.Functor.Contravariant

Methods

mempty :: Op a b #

mappend :: Op a b -> Op a b -> Op a b #

mconcat :: [Op a b] -> Op a b #

Monoid (Proxy s)

Since: base-4.7.0.0

Instance details

Defined in Data.Proxy

Methods

mempty :: Proxy s #

mappend :: Proxy s -> Proxy s -> Proxy s #

mconcat :: [Proxy s] -> Proxy s #

Monoid (U1 p)

Since: base-4.12.0.0

Instance details

Defined in GHC.Generics

Methods

mempty :: U1 p #

mappend :: U1 p -> U1 p -> U1 p #

mconcat :: [U1 p] -> U1 p #

Ord k => Monoid (Map k v) 
Instance details

Defined in Data.Map.Internal

Methods

mempty :: Map k v #

mappend :: Map k v -> Map k v -> Map k v #

mconcat :: [Map k v] -> Map k v #

(Eq k, Hashable k) => Monoid (HashMap k v)

mempty = empty

mappend = union

If a key occurs in both maps, the mapping from the first will be the mapping in the result.

Examples

Expand
>>> mappend (fromList [(1,'a'),(2,'b')]) (fromList [(2,'c'),(3,'d')])
fromList [(1,'a'),(2,'b'),(3,'d')]
Instance details

Defined in Data.HashMap.Internal

Methods

mempty :: HashMap k v #

mappend :: HashMap k v -> HashMap k v -> HashMap k v #

mconcat :: [HashMap k v] -> HashMap k v #

(Semigroup e, Monoid a) => Monoid (Validation e a)

mempty :: Validation e a is Success which stores mempty :: a to be consistent with the Semigroup instance.

Examples

>>> mempty :: Validation String [Bool]
Success []
Instance details

Defined in Validation

Methods

mempty :: Validation e a #

mappend :: Validation e a -> Validation e a -> Validation e a #

mconcat :: [Validation e a] -> Validation e a #

Monoid b => Monoid (a -> b)

Since: base-2.1

Instance details

Defined in GHC.Base

Methods

mempty :: a -> b #

mappend :: (a -> b) -> (a -> b) -> a -> b #

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

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

Since: base-2.1

Instance details

Defined in GHC.Base

Methods

mempty :: (a, b) #

mappend :: (a, b) -> (a, b) -> (a, b) #

mconcat :: [(a, b)] -> (a, b) #

Monoid a => Monoid (Const a b)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Const

Methods

mempty :: Const a b #

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

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

(Applicative f, Monoid a) => Monoid (Ap f a)

Since: base-4.12.0.0

Instance details

Defined in Data.Monoid

Methods

mempty :: Ap f a #

mappend :: Ap f a -> Ap f a -> Ap f a #

mconcat :: [Ap f a] -> Ap f a #

Alternative f => Monoid (Alt f a)

Since: base-4.8.0.0

Instance details

Defined in Data.Semigroup.Internal

Methods

mempty :: Alt f a #

mappend :: Alt f a -> Alt f a -> Alt f a #

mconcat :: [Alt f a] -> Alt f a #

Monoid (f p) => Monoid (Rec1 f p)

Since: base-4.12.0.0

Instance details

Defined in GHC.Generics

Methods

mempty :: Rec1 f p #

mappend :: Rec1 f p -> Rec1 f p -> Rec1 f p #

mconcat :: [Rec1 f p] -> Rec1 f p #

(Semigroup a, Monoid a) => Monoid (Tagged s a) 
Instance details

Defined in Data.Tagged

Methods

mempty :: Tagged s a #

mappend :: Tagged s a -> Tagged s a -> Tagged s a #

mconcat :: [Tagged s a] -> Tagged s a #

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

Since: base-2.1

Instance details

Defined in GHC.Base

Methods

mempty :: (a, b, c) #

mappend :: (a, b, c) -> (a, b, c) -> (a, b, c) #

mconcat :: [(a, b, c)] -> (a, b, c) #

(Monoid (f a), Monoid (g a)) => Monoid (Product f g a)

Since: base-4.16.0.0

Instance details

Defined in Data.Functor.Product

Methods

mempty :: Product f g a #

mappend :: Product f g a -> Product f g a -> Product f g a #

mconcat :: [Product f g a] -> Product f g a #

(Monoid (f p), Monoid (g p)) => Monoid ((f :*: g) p)

Since: base-4.12.0.0

Instance details

Defined in GHC.Generics

Methods

mempty :: (f :*: g) p #

mappend :: (f :*: g) p -> (f :*: g) p -> (f :*: g) p #

mconcat :: [(f :*: g) p] -> (f :*: g) p #

Monoid c => Monoid (K1 i c p)

Since: base-4.12.0.0

Instance details

Defined in GHC.Generics

Methods

mempty :: K1 i c p #

mappend :: K1 i c p -> K1 i c p -> K1 i c p #

mconcat :: [K1 i c p] -> K1 i c p #

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

Since: base-2.1

Instance details

Defined in GHC.Base

Methods

mempty :: (a, b, c, d) #

mappend :: (a, b, c, d) -> (a, b, c, d) -> (a, b, c, d) #

mconcat :: [(a, b, c, d)] -> (a, b, c, d) #

Monoid (f (g a)) => Monoid (Compose f g a)

Since: base-4.16.0.0

Instance details

Defined in Data.Functor.Compose

Methods

mempty :: Compose f g a #

mappend :: Compose f g a -> Compose f g a -> Compose f g a #

mconcat :: [Compose f g a] -> Compose f g a #

Monoid (f (g p)) => Monoid ((f :.: g) p)

Since: base-4.12.0.0

Instance details

Defined in GHC.Generics

Methods

mempty :: (f :.: g) p #

mappend :: (f :.: g) p -> (f :.: g) p -> (f :.: g) p #

mconcat :: [(f :.: g) p] -> (f :.: g) p #

Monoid (f p) => Monoid (M1 i c f p)

Since: base-4.12.0.0

Instance details

Defined in GHC.Generics

Methods

mempty :: M1 i c f p #

mappend :: M1 i c f p -> M1 i c f p -> M1 i c f p #

mconcat :: [M1 i c f p] -> M1 i c f p #

(Monoid a, Monoid b, Monoid c, Monoid d, Monoid e) => Monoid (a, b, c, d, e)

Since: base-2.1

Instance details

Defined in GHC.Base

Methods

mempty :: (a, b, c, d, e) #

mappend :: (a, b, c, d, e) -> (a, b, c, d, e) -> (a, b, c, d, e) #

mconcat :: [(a, b, c, d, e)] -> (a, b, c, d, e) #

mconcat :: Monoid a => [a] -> a #

Fold a list using the monoid.

For most types, the default definition for mconcat will be used, but the function is included in the class definition so that an optimized version can be provided for specific types.

>>> mconcat ["Hello", " ", "Haskell", "!"]
"Hello Haskell!"

ifTrue :: Monoid m => Bool -> m -> m Source #

If the predicate is true, return the m, else mempty.

This can be used (together with ifExists) to e.g. create lists with optional elements:

>>> import Data.Monoid (Sum(..))
>>> :{ mconcat [
  ifTrue (1 == 1) [1],
  [2, 3, 4],
  ifTrue False [5],
]
:}
[1,2,3,4]

Or any other Monoid:

>>> mconcat [ Sum 1, ifTrue (1 == 1) (Sum 2), Sum 3 ]

ifExists :: Monoid m => Maybe m -> m Source #

If the given Maybe is Just, return the m, else return mempty.

data Void #

Uninhabited data type

Since: base-4.8.0.0

Instances

Instances details
Data Void

Since: base-4.8.0.0

Instance details

Defined in Data.Void

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Void -> c Void #

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c Void #

toConstr :: Void -> Constr #

dataTypeOf :: Void -> DataType #

dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c Void) #

dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c Void) #

gmapT :: (forall b. Data b => b -> b) -> Void -> Void #

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Void -> r #

gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Void -> r #

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

gmapQi :: Int -> (forall d. Data d => d -> u) -> Void -> u #

gmapM :: Monad m => (forall d. Data d => d -> m d) -> Void -> m Void #

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Void -> m Void #

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Void -> m Void #

Semigroup Void

Since: base-4.9.0.0

Instance details

Defined in Data.Void

Methods

(<>) :: Void -> Void -> Void #

sconcat :: NonEmpty Void -> Void #

stimes :: Integral b => b -> Void -> Void #

Exception Void

Since: base-4.8.0.0

Instance details

Defined in Data.Void

Generic Void 
Instance details

Defined in Data.Void

Associated Types

type Rep Void :: Type -> Type #

Methods

from :: Void -> Rep Void x #

to :: Rep Void x -> Void #

Ix Void

Since: base-4.8.0.0

Instance details

Defined in Data.Void

Methods

range :: (Void, Void) -> [Void] #

index :: (Void, Void) -> Void -> Int #

unsafeIndex :: (Void, Void) -> Void -> Int #

inRange :: (Void, Void) -> Void -> Bool #

rangeSize :: (Void, Void) -> Int #

unsafeRangeSize :: (Void, Void) -> Int #

Read Void

Reading a Void value is always a parse error, considering Void as a data type with no constructors.

Since: base-4.8.0.0

Instance details

Defined in Data.Void

Show Void

Since: base-4.8.0.0

Instance details

Defined in Data.Void

Methods

showsPrec :: Int -> Void -> ShowS #

show :: Void -> String #

showList :: [Void] -> ShowS #

Eq Void

Since: base-4.8.0.0

Instance details

Defined in Data.Void

Methods

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

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

Ord Void

Since: base-4.8.0.0

Instance details

Defined in Data.Void

Methods

compare :: Void -> Void -> Ordering #

(<) :: Void -> Void -> Bool #

(<=) :: Void -> Void -> Bool #

(>) :: Void -> Void -> Bool #

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

max :: Void -> Void -> Void #

min :: Void -> Void -> Void #

Hashable Void 
Instance details

Defined in Data.Hashable.Class

Methods

hashWithSalt :: Int -> Void -> Int #

hash :: Void -> Int #

Lift Void

Since: template-haskell-2.15.0.0

Instance details

Defined in Language.Haskell.TH.Syntax

Methods

lift :: Quote m => Void -> m Exp #

liftTyped :: forall (m :: Type -> Type). Quote m => Void -> Code m Void #

type Rep Void

Since: base-4.8.0.0

Instance details

Defined in Data.Void

type Rep Void = D1 ('MetaData "Void" "Data.Void" "base" 'False) (V1 :: Type -> Type)

absurd :: Void -> a #

Since Void values logically don't exist, this witnesses the logical reasoning tool of "ex falso quodlibet".

>>> let x :: Either Void Int; x = Right 5
>>> :{
case x of
    Right r -> r
    Left l  -> absurd l
:}
5

Since: base-4.8.0.0

newtype Identity a #

Identity functor and monad. (a non-strict monad)

Since: base-4.8.0.0

Constructors

Identity 

Fields

Instances

Instances details
MonadFix Identity

Since: base-4.8.0.0

Instance details

Defined in Data.Functor.Identity

Methods

mfix :: (a -> Identity a) -> Identity a #

Foldable Identity

Since: base-4.8.0.0

Instance details

Defined in Data.Functor.Identity

Methods

fold :: Monoid m => Identity m -> m #

foldMap :: Monoid m => (a -> m) -> Identity a -> m #

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

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

foldr' :: (a -> b -> b) -> b -> Identity a -> b #

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

foldl' :: (b -> a -> b) -> b -> Identity a -> b #

foldr1 :: (a -> a -> a) -> Identity a -> a #

foldl1 :: (a -> a -> a) -> Identity a -> a #

toList :: Identity a -> [a] #

null :: Identity a -> Bool #

length :: Identity a -> Int #

elem :: Eq a => a -> Identity a -> Bool #

maximum :: Ord a => Identity a -> a #

minimum :: Ord a => Identity a -> a #

sum :: Num a => Identity a -> a #

product :: Num a => Identity a -> a #

Eq1 Identity

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

liftEq :: (a -> b -> Bool) -> Identity a -> Identity b -> Bool #

Ord1 Identity

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

liftCompare :: (a -> b -> Ordering) -> Identity a -> Identity b -> Ordering #

Read1 Identity

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

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

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

liftReadPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec (Identity a) #

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

Show1 Identity

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

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

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

Traversable Identity

Since: base-4.9.0.0

Instance details

Defined in Data.Traversable

Methods

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

sequenceA :: Applicative f => Identity (f a) -> f (Identity a) #

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

sequence :: Monad m => Identity (m a) -> m (Identity a) #

Applicative Identity

Since: base-4.8.0.0

Instance details

Defined in Data.Functor.Identity

Methods

pure :: a -> Identity a #

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

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

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

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

Functor Identity

Since: base-4.8.0.0

Instance details

Defined in Data.Functor.Identity

Methods

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

(<$) :: a -> Identity b -> Identity a #

Monad Identity

Since: base-4.8.0.0

Instance details

Defined in Data.Functor.Identity

Methods

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

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

return :: a -> Identity a #

Comonad Identity 
Instance details

Defined in Control.Comonad

Methods

extract :: Identity a -> a #

duplicate :: Identity a -> Identity (Identity a) #

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

ComonadApply Identity 
Instance details

Defined in Control.Comonad

Methods

(<@>) :: Identity (a -> b) -> Identity a -> Identity b #

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

(<@) :: Identity a -> Identity b -> Identity a #

Foldable1 Identity 
Instance details

Defined in Data.Foldable1

Methods

fold1 :: Semigroup m => Identity m -> m #

foldMap1 :: Semigroup m => (a -> m) -> Identity a -> m #

foldMap1' :: Semigroup m => (a -> m) -> Identity a -> m #

toNonEmpty :: Identity a -> NonEmpty a #

maximum :: Ord a => Identity a -> a #

minimum :: Ord a => Identity a -> a #

head :: Identity a -> a #

last :: Identity a -> a #

foldrMap1 :: (a -> b) -> (a -> b -> b) -> Identity a -> b #

foldlMap1' :: (a -> b) -> (b -> a -> b) -> Identity a -> b #

foldlMap1 :: (a -> b) -> (b -> a -> b) -> Identity a -> b #

foldrMap1' :: (a -> b) -> (a -> b -> b) -> Identity a -> b #

Hashable1 Identity 
Instance details

Defined in Data.Hashable.Class

Methods

liftHashWithSalt :: (Int -> a -> Int) -> Int -> Identity a -> Int #

Alt Identity

Choose the first option every time. While 'choose the last option' every time is also valid, this instance satisfies more laws.

Since: semigroupoids-5.3.6

Instance details

Defined in Data.Functor.Alt

Apply Identity 
Instance details

Defined in Data.Functor.Bind.Class

Methods

(<.>) :: Identity (a -> b) -> Identity a -> Identity b #

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

(<.) :: Identity a -> Identity b -> Identity a #

liftF2 :: (a -> b -> c) -> Identity a -> Identity b -> Identity c #

Bind Identity 
Instance details

Defined in Data.Functor.Bind.Class

Methods

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

join :: Identity (Identity a) -> Identity a #

Extend Identity 
Instance details

Defined in Data.Functor.Extend

Methods

duplicated :: Identity a -> Identity (Identity a) #

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

Traversable1 Identity 
Instance details

Defined in Data.Semigroup.Traversable.Class

Methods

traverse1 :: Apply f => (a -> f b) -> Identity a -> f (Identity b) #

sequence1 :: Apply f => Identity (f b) -> f (Identity b) #

Generic1 Identity 
Instance details

Defined in Data.Functor.Identity

Associated Types

type Rep1 Identity :: k -> Type #

Methods

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

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

Data a => Data (Identity a)

Since: base-4.9.0.0

Instance details

Defined in Data.Data

Methods

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

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

toConstr :: Identity a -> Constr #

dataTypeOf :: Identity a -> DataType #

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

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

gmapT :: (forall b. Data b => b -> b) -> Identity a -> Identity a #

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Identity a -> r #

gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Identity a -> r #

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

gmapQi :: Int -> (forall d. Data d => d -> u) -> Identity a -> u #

gmapM :: Monad m => (forall d. Data d => d -> m d) -> Identity a -> m (Identity a) #

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Identity a -> m (Identity a) #

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Identity a -> m (Identity a) #

Storable a => Storable (Identity a)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Identity

Methods

sizeOf :: Identity a -> Int #

alignment :: Identity a -> Int #

peekElemOff :: Ptr (Identity a) -> Int -> IO (Identity a) #

pokeElemOff :: Ptr (Identity a) -> Int -> Identity a -> IO () #

peekByteOff :: Ptr b -> Int -> IO (Identity a) #

pokeByteOff :: Ptr b -> Int -> Identity a -> IO () #

peek :: Ptr (Identity a) -> IO (Identity a) #

poke :: Ptr (Identity a) -> Identity a -> IO () #

Monoid a => Monoid (Identity a)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Identity

Methods

mempty :: Identity a #

mappend :: Identity a -> Identity a -> Identity a #

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

Semigroup a => Semigroup (Identity a)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Identity

Methods

(<>) :: Identity a -> Identity a -> Identity a #

sconcat :: NonEmpty (Identity a) -> Identity a #

stimes :: Integral b => b -> Identity a -> Identity a #

Bits a => Bits (Identity a)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Identity

FiniteBits a => FiniteBits (Identity a)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Identity

Bounded a => Bounded (Identity a)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Identity

Enum a => Enum (Identity a)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Identity

Floating a => Floating (Identity a)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Identity

RealFloat a => RealFloat (Identity a)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Identity

Generic (Identity a) 
Instance details

Defined in Data.Functor.Identity

Associated Types

type Rep (Identity a) :: Type -> Type #

Methods

from :: Identity a -> Rep (Identity a) x #

to :: Rep (Identity a) x -> Identity a #

Ix a => Ix (Identity a)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Identity

Num a => Num (Identity a)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Identity

Read a => Read (Identity a)

This instance would be equivalent to the derived instances of the Identity newtype if the runIdentity field were removed

Since: base-4.8.0.0

Instance details

Defined in Data.Functor.Identity

Fractional a => Fractional (Identity a)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Identity

Integral a => Integral (Identity a)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Identity

Real a => Real (Identity a)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Identity

Methods

toRational :: Identity a -> Rational #

RealFrac a => RealFrac (Identity a)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Identity

Methods

properFraction :: Integral b => Identity a -> (b, Identity a) #

truncate :: Integral b => Identity a -> b #

round :: Integral b => Identity a -> b #

ceiling :: Integral b => Identity a -> b #

floor :: Integral b => Identity a -> b #

Show a => Show (Identity a)

This instance would be equivalent to the derived instances of the Identity newtype if the runIdentity field were removed

Since: base-4.8.0.0

Instance details

Defined in Data.Functor.Identity

Methods

showsPrec :: Int -> Identity a -> ShowS #

show :: Identity a -> String #

showList :: [Identity a] -> ShowS #

Eq a => Eq (Identity a)

Since: base-4.8.0.0

Instance details

Defined in Data.Functor.Identity

Methods

(==) :: Identity a -> Identity a -> Bool #

(/=) :: Identity a -> Identity a -> Bool #

Ord a => Ord (Identity a)

Since: base-4.8.0.0

Instance details

Defined in Data.Functor.Identity

Methods

compare :: Identity a -> Identity a -> Ordering #

(<) :: Identity a -> Identity a -> Bool #

(<=) :: Identity a -> Identity a -> Bool #

(>) :: Identity a -> Identity a -> Bool #

(>=) :: Identity a -> Identity a -> Bool #

max :: Identity a -> Identity a -> Identity a #

min :: Identity a -> Identity a -> Identity a #

Hashable a => Hashable (Identity a) 
Instance details

Defined in Data.Hashable.Class

Methods

hashWithSalt :: Int -> Identity a -> Int #

hash :: Identity a -> Int #

type Rep1 Identity

Since: base-4.8.0.0

Instance details

Defined in Data.Functor.Identity

type Rep1 Identity = D1 ('MetaData "Identity" "Data.Functor.Identity" "base" 'True) (C1 ('MetaCons "Identity" 'PrefixI 'True) (S1 ('MetaSel ('Just "runIdentity") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) Par1))
type Rep (Identity a)

Since: base-4.8.0.0

Instance details

Defined in Data.Functor.Identity

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

data Natural #

Natural number

Invariant: numbers <= 0xffffffffffffffff use the NS constructor

Instances

Instances details
Data Natural

Since: base-4.8.0.0

Instance details

Defined in Data.Data

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Natural -> c Natural #

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c Natural #

toConstr :: Natural -> Constr #

dataTypeOf :: Natural -> DataType #

dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c Natural) #

dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c Natural) #

gmapT :: (forall b. Data b => b -> b) -> Natural -> Natural #

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Natural -> r #

gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Natural -> r #

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

gmapQi :: Int -> (forall d. Data d => d -> u) -> Natural -> u #

gmapM :: Monad m => (forall d. Data d => d -> m d) -> Natural -> m Natural #

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Natural -> m Natural #

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Natural -> m Natural #

Enum Natural

Since: base-4.8.0.0

Instance details

Defined in GHC.Enum

Ix Natural

Since: base-4.8.0.0

Instance details

Defined in GHC.Ix

Num Natural

Note that Natural's Num instance isn't a ring: no element but 0 has an additive inverse. It is a semiring though.

Since: base-4.8.0.0

Instance details

Defined in GHC.Num

Read Natural

Since: base-4.8.0.0

Instance details

Defined in GHC.Read

Integral Natural

Since: base-4.8.0.0

Instance details

Defined in GHC.Real

Real Natural

Since: base-4.8.0.0

Instance details

Defined in GHC.Real

Show Natural

Since: base-4.8.0.0

Instance details

Defined in GHC.Show

Eq Natural 
Instance details

Defined in GHC.Num.Natural

Methods

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

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

Ord Natural 
Instance details

Defined in GHC.Num.Natural

Hashable Natural 
Instance details

Defined in Data.Hashable.Class

Methods

hashWithSalt :: Int -> Natural -> Int #

hash :: Natural -> Int #

Lift Natural 
Instance details

Defined in Language.Haskell.TH.Syntax

Methods

lift :: Quote m => Natural -> m Exp #

liftTyped :: forall (m :: Type -> Type). Quote m => Natural -> Code m Natural #

type PyFClassify Natural 
Instance details

Defined in PyF.Class

intToNatural :: Integral a => a -> Maybe Natural Source #

Convert an integer to a Natural if possible

Named the same as the function from GHC.Natural, but does not crash.

class Contravariant (f :: Type -> Type) #

The class of contravariant functors.

Whereas in Haskell, one can think of a Functor as containing or producing values, a contravariant functor is a functor that can be thought of as consuming values.

As an example, consider the type of predicate functions a -> Bool. One such predicate might be negative x = x < 0, which classifies integers as to whether they are negative. However, given this predicate, we can re-use it in other situations, providing we have a way to map values to integers. For instance, we can use the negative predicate on a person's bank balance to work out if they are currently overdrawn:

newtype Predicate a = Predicate { getPredicate :: a -> Bool }

instance Contravariant Predicate where
  contramap :: (a' -> a) -> (Predicate a -> Predicate a')
  contramap f (Predicate p) = Predicate (p . f)
                                         |   `- First, map the input...
                                         `----- then apply the predicate.

overdrawn :: Predicate Person
overdrawn = contramap personBankBalance negative

Any instance should be subject to the following laws:

Identity
contramap id = id
Composition
contramap (g . f) = contramap f . contramap g

Note, that the second law follows from the free theorem of the type of contramap and the first law, so you need only check that the former condition holds.

Minimal complete definition

contramap

Instances

Instances details
Contravariant Comparison

A Comparison is a Contravariant Functor, because contramap can apply its function argument to each input of the comparison function.

Instance details

Defined in Data.Functor.Contravariant

Methods

contramap :: (a' -> a) -> Comparison a -> Comparison a' #

(>$) :: b -> Comparison b -> Comparison a #

Contravariant Equivalence

Equivalence relations are Contravariant, because you can apply the contramapped function to each input to the equivalence relation.

Instance details

Defined in Data.Functor.Contravariant

Methods

contramap :: (a' -> a) -> Equivalence a -> Equivalence a' #

(>$) :: b -> Equivalence b -> Equivalence a #

Contravariant Predicate

A Predicate is a Contravariant Functor, because contramap can apply its function argument to the input of the predicate.

Without newtypes contramap f equals precomposing with f (= (. f)).

contramap :: (a' -> a) -> (Predicate a -> Predicate a')
contramap f (Predicate g) = Predicate (g . f)
Instance details

Defined in Data.Functor.Contravariant

Methods

contramap :: (a' -> a) -> Predicate a -> Predicate a' #

(>$) :: b -> Predicate b -> Predicate a #

Contravariant (Op a) 
Instance details

Defined in Data.Functor.Contravariant

Methods

contramap :: (a' -> a0) -> Op a a0 -> Op a a' #

(>$) :: b -> Op a b -> Op a a0 #

Contravariant (Proxy :: Type -> Type) 
Instance details

Defined in Data.Functor.Contravariant

Methods

contramap :: (a' -> a) -> Proxy a -> Proxy a' #

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

Contravariant (U1 :: Type -> Type) 
Instance details

Defined in Data.Functor.Contravariant

Methods

contramap :: (a' -> a) -> U1 a -> U1 a' #

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

Contravariant (V1 :: Type -> Type) 
Instance details

Defined in Data.Functor.Contravariant

Methods

contramap :: (a' -> a) -> V1 a -> V1 a' #

(>$) :: b -> V1 b -> V1 a #

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

Defined in Data.Functor.Contravariant

Methods

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

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

Contravariant f => Contravariant (Alt f) 
Instance details

Defined in Data.Functor.Contravariant

Methods

contramap :: (a' -> a) -> Alt f a -> Alt f a' #

(>$) :: b -> Alt f b -> Alt f a #

Contravariant f => Contravariant (Rec1 f) 
Instance details

Defined in Data.Functor.Contravariant

Methods

contramap :: (a' -> a) -> Rec1 f a -> Rec1 f a' #

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

Contravariant f => Contravariant (Backwards f)

Derived instance.

Instance details

Defined in Control.Applicative.Backwards

Methods

contramap :: (a' -> a) -> Backwards f a -> Backwards f a' #

(>$) :: b -> Backwards f b -> Backwards f a #

Contravariant m => Contravariant (ErrorT e m) 
Instance details

Defined in Control.Monad.Trans.Error

Methods

contramap :: (a' -> a) -> ErrorT e m a -> ErrorT e m a' #

(>$) :: b -> ErrorT e m b -> ErrorT e m a #

Contravariant m => Contravariant (ExceptT e m) 
Instance details

Defined in Control.Monad.Trans.Except

Methods

contramap :: (a' -> a) -> ExceptT e m a -> ExceptT e m a' #

(>$) :: b -> ExceptT e m b -> ExceptT e m a #

Contravariant f => Contravariant (IdentityT f) 
Instance details

Defined in Control.Monad.Trans.Identity

Methods

contramap :: (a' -> a) -> IdentityT f a -> IdentityT f a' #

(>$) :: b -> IdentityT f b -> IdentityT f a #

Contravariant f => Contravariant (Reverse f)

Derived instance.

Instance details

Defined in Data.Functor.Reverse

Methods

contramap :: (a' -> a) -> Reverse f a -> Reverse f a' #

(>$) :: b -> Reverse f b -> Reverse f a #

(Contravariant f, Contravariant g) => Contravariant (Product f g) 
Instance details

Defined in Data.Functor.Contravariant

Methods

contramap :: (a' -> a) -> Product f g a -> Product f g a' #

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

(Contravariant f, Contravariant g) => Contravariant (Sum f g) 
Instance details

Defined in Data.Functor.Contravariant

Methods

contramap :: (a' -> a) -> Sum f g a -> Sum f g a' #

(>$) :: b -> Sum f g b -> Sum f g a #

(Contravariant f, Contravariant g) => Contravariant (f :*: g) 
Instance details

Defined in Data.Functor.Contravariant

Methods

contramap :: (a' -> a) -> (f :*: g) a -> (f :*: g) a' #

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

(Contravariant f, Contravariant g) => Contravariant (f :+: g) 
Instance details

Defined in Data.Functor.Contravariant

Methods

contramap :: (a' -> a) -> (f :+: g) a -> (f :+: g) a' #

(>$) :: b -> (f :+: g) b -> (f :+: g) a #

Contravariant (K1 i c :: Type -> Type) 
Instance details

Defined in Data.Functor.Contravariant

Methods

contramap :: (a' -> a) -> K1 i c a -> K1 i c a' #

(>$) :: b -> K1 i c b -> K1 i c a #

(Functor f, Contravariant g) => Contravariant (Compose f g) 
Instance details

Defined in Data.Functor.Contravariant

Methods

contramap :: (a' -> a) -> Compose f g a -> Compose f g a' #

(>$) :: b -> Compose f g b -> Compose f g a #

(Functor f, Contravariant g) => Contravariant (f :.: g) 
Instance details

Defined in Data.Functor.Contravariant

Methods

contramap :: (a' -> a) -> (f :.: g) a -> (f :.: g) a' #

(>$) :: b -> (f :.: g) b -> (f :.: g) a #

Contravariant f => Contravariant (M1 i c f) 
Instance details

Defined in Data.Functor.Contravariant

Methods

contramap :: (a' -> a) -> M1 i c f a -> M1 i c f a' #

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

contramap :: Contravariant f => (a' -> a) -> f a -> f a' #

(>$<) :: Contravariant f => (a -> b) -> f b -> f a infixl 4 #

This is an infix alias for contramap.

(>&<) :: Contravariant f => f b -> (a -> b) -> f a infixl 5 Source #

Forward-applying contramap, like &$ and <&><$> but for >$<.

class Profunctor (p :: Type -> Type -> Type) #

Formally, the class Profunctor represents a profunctor from Hask -> Hask.

Intuitively it is a bifunctor where the first argument is contravariant and the second argument is covariant.

You can define a Profunctor by either defining dimap or by defining both lmap and rmap.

If you supply dimap, you should ensure that:

dimap id idid

If you supply lmap and rmap, ensure:

lmap idid
rmap idid

If you supply both, you should also ensure:

dimap f g ≡ lmap f . rmap g

These ensure by parametricity:

dimap (f . g) (h . i) ≡ dimap g h . dimap f i
lmap (f . g) ≡ lmap g . lmap f
rmap (f . g) ≡ rmap f . rmap g

Minimal complete definition

dimap | lmap, rmap

Instances

Instances details
Monad m => Profunctor (Kleisli m) 
Instance details

Defined in Data.Profunctor.Unsafe

Methods

dimap :: (a -> b) -> (c -> d) -> Kleisli m b c -> Kleisli m a d #

lmap :: (a -> b) -> Kleisli m b c -> Kleisli m a c #

rmap :: (b -> c) -> Kleisli m a b -> Kleisli m a c #

(#.) :: forall a b c q. Coercible c b => q b c -> Kleisli m a b -> Kleisli m a c #

(.#) :: forall a b c q. Coercible b a => Kleisli m b c -> q a b -> Kleisli m a c #

Profunctor (Tagged :: Type -> Type -> Type) 
Instance details

Defined in Data.Profunctor.Unsafe

Methods

dimap :: (a -> b) -> (c -> d) -> Tagged b c -> Tagged a d #

lmap :: (a -> b) -> Tagged b c -> Tagged a c #

rmap :: (b -> c) -> Tagged a b -> Tagged a c #

(#.) :: forall a b c q. Coercible c b => q b c -> Tagged a b -> Tagged a c #

(.#) :: forall a b c q. Coercible b a => Tagged b c -> q a b -> Tagged a c #

Functor w => Profunctor (Cokleisli w) 
Instance details

Defined in Data.Profunctor.Unsafe

Methods

dimap :: (a -> b) -> (c -> d) -> Cokleisli w b c -> Cokleisli w a d #

lmap :: (a -> b) -> Cokleisli w b c -> Cokleisli w a c #

rmap :: (b -> c) -> Cokleisli w a b -> Cokleisli w a c #

(#.) :: forall a b c q. Coercible c b => q b c -> Cokleisli w a b -> Cokleisli w a c #

(.#) :: forall a b c q. Coercible b a => Cokleisli w b c -> q a b -> Cokleisli w a c #

Profunctor (->) 
Instance details

Defined in Data.Profunctor.Unsafe

Methods

dimap :: (a -> b) -> (c -> d) -> (b -> c) -> a -> d #

lmap :: (a -> b) -> (b -> c) -> a -> c #

rmap :: (b -> c) -> (a -> b) -> a -> c #

(#.) :: forall a b c q. Coercible c b => q b c -> (a -> b) -> a -> c #

(.#) :: forall a b c q. Coercible b a => (b -> c) -> q a b -> a -> c #

Contravariant f => Profunctor (Clown f :: Type -> Type -> Type) 
Instance details

Defined in Data.Profunctor.Unsafe

Methods

dimap :: (a -> b) -> (c -> d) -> Clown f b c -> Clown f a d #

lmap :: (a -> b) -> Clown f b c -> Clown f a c #

rmap :: (b -> c) -> Clown f a b -> Clown f a c #

(#.) :: forall a b c q. Coercible c b => q b c -> Clown f a b -> Clown f a c #

(.#) :: forall a b c q. Coercible b a => Clown f b c -> q a b -> Clown f a c #

Functor f => Profunctor (Joker f :: Type -> Type -> Type) 
Instance details

Defined in Data.Profunctor.Unsafe

Methods

dimap :: (a -> b) -> (c -> d) -> Joker f b c -> Joker f a d #

lmap :: (a -> b) -> Joker f b c -> Joker f a c #

rmap :: (b -> c) -> Joker f a b -> Joker f a c #

(#.) :: forall a b c q. Coercible c b => q b c -> Joker f a b -> Joker f a c #

(.#) :: forall a b c q. Coercible b a => Joker f b c -> q a b -> Joker f a c #

(Profunctor p, Profunctor q) => Profunctor (Product p q) 
Instance details

Defined in Data.Profunctor.Unsafe

Methods

dimap :: (a -> b) -> (c -> d) -> Product p q b c -> Product p q a d #

lmap :: (a -> b) -> Product p q b c -> Product p q a c #

rmap :: (b -> c) -> Product p q a b -> Product p q a c #

(#.) :: forall a b c q0. Coercible c b => q0 b c -> Product p q a b -> Product p q a c #

(.#) :: forall a b c q0. Coercible b a => Product p q b c -> q0 a b -> Product p q a c #

(Profunctor p, Profunctor q) => Profunctor (Sum p q) 
Instance details

Defined in Data.Profunctor.Unsafe

Methods

dimap :: (a -> b) -> (c -> d) -> Sum p q b c -> Sum p q a d #

lmap :: (a -> b) -> Sum p q b c -> Sum p q a c #

rmap :: (b -> c) -> Sum p q a b -> Sum p q a c #

(#.) :: forall a b c q0. Coercible c b => q0 b c -> Sum p q a b -> Sum p q a c #

(.#) :: forall a b c q0. Coercible b a => Sum p q b c -> q0 a b -> Sum p q a c #

(Functor f, Profunctor p) => Profunctor (Tannen f p) 
Instance details

Defined in Data.Profunctor.Unsafe

Methods

dimap :: (a -> b) -> (c -> d) -> Tannen f p b c -> Tannen f p a d #

lmap :: (a -> b) -> Tannen f p b c -> Tannen f p a c #

rmap :: (b -> c) -> Tannen f p a b -> Tannen f p a c #

(#.) :: forall a b c q. Coercible c b => q b c -> Tannen f p a b -> Tannen f p a c #

(.#) :: forall a b c q. Coercible b a => Tannen f p b c -> q a b -> Tannen f p a c #

(Profunctor p, Functor f, Functor g) => Profunctor (Biff p f g) 
Instance details

Defined in Data.Profunctor.Unsafe

Methods

dimap :: (a -> b) -> (c -> d) -> Biff p f g b c -> Biff p f g a d #

lmap :: (a -> b) -> Biff p f g b c -> Biff p f g a c #

rmap :: (b -> c) -> Biff p f g a b -> Biff p f g a c #

(#.) :: forall a b c q. Coercible c b => q b c -> Biff p f g a b -> Biff p f g a c #

(.#) :: forall a b c q. Coercible b a => Biff p f g b c -> q a b -> Biff p f g a c #

dimap :: Profunctor p => (a -> b) -> (c -> d) -> p b c -> p a d #

Map over both arguments at the same time.

dimap f g ≡ lmap f . rmap g

lmap :: Profunctor p => (a -> b) -> p b c -> p a c #

Map the first argument contravariantly.

lmap f ≡ dimap f id

rmap :: Profunctor p => (b -> c) -> p a b -> p a c #

Map the second argument covariantly.

rmapdimap id

class Semigroupoid (c :: k -> k -> Type) #

Minimal complete definition

o

Instances

Instances details
Semigroupoid Op 
Instance details

Defined in Data.Semigroupoid

Methods

o :: forall (j :: k) (k1 :: k) (i :: k). Op j k1 -> Op i j -> Op i k1 #

Semigroupoid (,)

http://en.wikipedia.org/wiki/Band_(mathematics)#Rectangular_bands

Instance details

Defined in Data.Semigroupoid

Methods

o :: forall (j :: k) (k1 :: k) (i :: k). (j, k1) -> (i, j) -> (i, k1) #

Bind m => Semigroupoid (Kleisli m :: Type -> Type -> TYPE LiftedRep) 
Instance details

Defined in Data.Semigroupoid

Methods

o :: forall (j :: k) (k1 :: k) (i :: k). Kleisli m j k1 -> Kleisli m i j -> Kleisli m i k1 #

Semigroupoid (Const :: Type -> Type -> Type) 
Instance details

Defined in Data.Semigroupoid

Methods

o :: forall (j :: k) (k1 :: k) (i :: k). Const j k1 -> Const i j -> Const i k1 #

Semigroupoid (Tagged :: Type -> Type -> Type) 
Instance details

Defined in Data.Semigroupoid

Methods

o :: forall (j :: k) (k1 :: k) (i :: k). Tagged j k1 -> Tagged i j -> Tagged i k1 #

Semigroupoid (Coercion :: k -> k -> Type) 
Instance details

Defined in Data.Semigroupoid

Methods

o :: forall (j :: k0) (k1 :: k0) (i :: k0). Coercion j k1 -> Coercion i j -> Coercion i k1 #

Semigroupoid ((:~:) :: k -> k -> Type) 
Instance details

Defined in Data.Semigroupoid

Methods

o :: forall (j :: k0) (k1 :: k0) (i :: k0). (j :~: k1) -> (i :~: j) -> i :~: k1 #

Extend w => Semigroupoid (Cokleisli w :: Type -> Type -> TYPE LiftedRep) 
Instance details

Defined in Data.Semigroupoid

Methods

o :: forall (j :: k) (k1 :: k) (i :: k). Cokleisli w j k1 -> Cokleisli w i j -> Cokleisli w i k1 #

Semigroupoid (->) 
Instance details

Defined in Data.Semigroupoid

Methods

o :: forall (j :: k) (k1 :: k) (i :: k). (j -> k1) -> (i -> j) -> i -> k1 #

Semigroupoid ((:~~:) :: k -> k -> Type) 
Instance details

Defined in Data.Semigroupoid

Methods

o :: forall (j :: k0) (k1 :: k0) (i :: k0). (j :~~: k1) -> (i :~~: j) -> i :~~: k1 #

Semigroup m => Semigroupoid (Semi m :: k -> k -> Type) 
Instance details

Defined in Data.Semigroupoid

Methods

o :: forall (j :: k0) (k1 :: k0) (i :: k0). Semi m j k1 -> Semi m i j -> Semi m i k1 #

Category k2 => Semigroupoid (WrappedCategory k2 :: k1 -> k1 -> Type) 
Instance details

Defined in Data.Semigroupoid

Methods

o :: forall (j :: k) (k10 :: k) (i :: k). WrappedCategory k2 j k10 -> WrappedCategory k2 i j -> WrappedCategory k2 i k10 #

class Category (cat :: k -> k -> Type) #

A class for categories. Instances should satisfy the laws

Right identity
f . id = f
Left identity
id . f = f
Associativity
f . (g . h) = (f . g) . h

Minimal complete definition

id, (.)

Instances

Instances details
Category Op 
Instance details

Defined in Data.Functor.Contravariant

Methods

id :: forall (a :: k). Op a a #

(.) :: forall (b :: k) (c :: k) (a :: k). Op b c -> Op a b -> Op a c #

Monad m => Category (Kleisli m :: Type -> Type -> TYPE LiftedRep)

Since: base-3.0

Instance details

Defined in Control.Arrow

Methods

id :: forall (a :: k). Kleisli m a a #

(.) :: forall (b :: k) (c :: k) (a :: k). Kleisli m b c -> Kleisli m a b -> Kleisli m a c #

(Applicative f, Monad f) => Category (WhenMissing f :: Type -> Type -> Type)

Since: containers-0.5.9

Instance details

Defined in Data.IntMap.Internal

Methods

id :: forall (a :: k). WhenMissing f a a #

(.) :: forall (b :: k) (c :: k) (a :: k). WhenMissing f b c -> WhenMissing f a b -> WhenMissing f a c #

Category (Coercion :: k -> k -> Type)

Since: base-4.7.0.0

Instance details

Defined in Control.Category

Methods

id :: forall (a :: k0). Coercion a a #

(.) :: forall (b :: k0) (c :: k0) (a :: k0). Coercion b c -> Coercion a b -> Coercion a c #

Category ((:~:) :: k -> k -> Type)

Since: base-4.7.0.0

Instance details

Defined in Control.Category

Methods

id :: forall (a :: k0). a :~: a #

(.) :: forall (b :: k0) (c :: k0) (a :: k0). (b :~: c) -> (a :~: b) -> a :~: c #

Comonad w => Category (Cokleisli w :: Type -> Type -> TYPE LiftedRep) 
Instance details

Defined in Control.Comonad

Methods

id :: forall (a :: k). Cokleisli w a a #

(.) :: forall (b :: k) (c :: k) (a :: k). Cokleisli w b c -> Cokleisli w a b -> Cokleisli w a c #

(Monad f, Applicative f) => Category (WhenMatched f x :: Type -> Type -> TYPE LiftedRep)

Since: containers-0.5.9

Instance details

Defined in Data.IntMap.Internal

Methods

id :: forall (a :: k). WhenMatched f x a a #

(.) :: forall (b :: k) (c :: k) (a :: k). WhenMatched f x b c -> WhenMatched f x a b -> WhenMatched f x a c #

(Applicative f, Monad f) => Category (WhenMissing f k :: Type -> Type -> Type)

Since: containers-0.5.9

Instance details

Defined in Data.Map.Internal

Methods

id :: forall (a :: k0). WhenMissing f k a a #

(.) :: forall (b :: k0) (c :: k0) (a :: k0). WhenMissing f k b c -> WhenMissing f k a b -> WhenMissing f k a c #

Category (->)

Since: base-3.0

Instance details

Defined in Control.Category

Methods

id :: forall (a :: k). a -> a #

(.) :: forall (b :: k) (c :: k) (a :: k). (b -> c) -> (a -> b) -> a -> c #

Category ((:~~:) :: k -> k -> Type)

Since: base-4.10.0.0

Instance details

Defined in Control.Category

Methods

id :: forall (a :: k0). a :~~: a #

(.) :: forall (b :: k0) (c :: k0) (a :: k0). (b :~~: c) -> (a :~~: b) -> a :~~: c #

(Monad f, Applicative f) => Category (WhenMatched f k x :: Type -> Type -> TYPE LiftedRep)

Since: containers-0.5.9

Instance details

Defined in Data.Map.Internal

Methods

id :: forall (a :: k0). WhenMatched f k x a a #

(.) :: forall (b :: k0) (c :: k0) (a :: k0). WhenMatched f k x b c -> WhenMatched f k x a b -> WhenMatched f k x a c #

Monoid m => Category (Semi m :: k -> k -> Type) 
Instance details

Defined in Data.Semigroupoid

Methods

id :: forall (a :: k0). Semi m a a #

(.) :: forall (b :: k0) (c :: k0) (a :: k0). Semi m b c -> Semi m a b -> Semi m a c #

Category k2 => Category (WrappedCategory k2 :: k1 -> k1 -> Type) 
Instance details

Defined in Data.Semigroupoid

Methods

id :: forall (a :: k). WrappedCategory k2 a a #

(.) :: forall (b :: k) (c :: k) (a :: k). WrappedCategory k2 b c -> WrappedCategory k2 a b -> WrappedCategory k2 a c #

(Category p, Category q) => Category (Product p q :: k -> k -> Type) 
Instance details

Defined in Data.Bifunctor.Product

Methods

id :: forall (a :: k0). Product p q a a #

(.) :: forall (b :: k0) (c :: k0) (a :: k0). Product p q b c -> Product p q a b -> Product p q a c #

(Applicative f, Category p) => Category (Tannen f p :: k -> k -> Type) 
Instance details

Defined in Data.Bifunctor.Tannen

Methods

id :: forall (a :: k0). Tannen f p a a #

(.) :: forall (b :: k0) (c :: k0) (a :: k0). Tannen f p b c -> Tannen f p a b -> Tannen f p a c #

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

Left-to-right composition

(&>>) :: Semigroupoid s => s a b -> s b c -> s a c infixr 1 Source #

Forward semigroupoid application. The same as (>>>), but Semigroupoid is not a superclass of Category (yet).

Specialized examples:

@ for functions : (a -> b) -> (b -> c) -> (a -> c) for Folds: Fold a b -> Fold b c -> Fold a c @

type family Any :: k where ... #

The type constructor Any is type to which you can unsafely coerce any lifted type, and back. More concretely, for a lifted type t and value x :: t, -- unsafeCoerce (unsafeCoerce x :: Any) :: t is equivalent to x.

Enum definition

inverseFunction :: forall a k. (Bounded a, Enum a, Ord k) => (a -> k) -> k -> Maybe a Source #

inverseFunction f creates a function that is the inverse of a given function f. It does so by constructing Map internally for each value f a. The implementation makes sure that the Map is constructed only once and then shared for every call.

Memory usage note: don't inverse functions that have types like Int as their result. In this case the created Map will have huge size.

The complexity of reversed mapping is \(\mathcal{O}(\log n)\).

Performance note: make sure to specialize monomorphic type of your functions that use inverseFunction to avoid Map reconstruction.

One of the common inverseFunction use-case is inverting the show or a show-like function.

>>> data Color = Red | Green | Blue deriving (Show, Enum, Bounded)
>>> parse = inverseFunction show :: String -> Maybe Color
>>> parse "Red"
Just Red
>>> parse "Black"
Nothing

Correctness note: inverseFunction expects injective function as its argument, i.e. the function must map distinct arguments to distinct values.

Typical usage of this function looks like this:

@ data GhcVer = Ghc802 | Ghc822 | Ghc844 | Ghc865 | Ghc881 deriving (Eq, Ord, Show, Enum, Bounded)

showGhcVer :: GhcVer -> Text showGhcVer = \case Ghc802 -> "8.0.2" Ghc822 -> "8.2.2" Ghc844 -> "8.4.4" Ghc865 -> "8.6.5" Ghc881 -> "8.8.1"

parseGhcVer :: Text -> Maybe GhcVer parseGhcVer = inverseFunction showGhcVer

Taken from relude’s Relude.Extra.Enum.

inverseMap :: forall a k. (Bounded a, Enum a, Ord k) => (a -> k) -> Map k a Source #

Like inverseFunction, but instead of returning the function it returns a mapping from all possible outputs to their possible inputs.

This has the same restrictions of inverseFunction.

enumerateAll :: (Enum a, Bounded a) => [a] Source #

All possible values in this enum.

Map helpers

mapFromListOn :: Ord key => (a -> key) -> [a] -> Map key a Source #

Create a Map from a list of values, extracting the map key from each value. Like fromList.

Attention: if the key is not unique, the earliest value with the key will be in the map.

mapFromListOnMerge :: (Ord key, Semigroup s) => (a -> (key, s)) -> [a] -> Map key s Source #

Create a Map from a list of values, merging multiple values at the same key with <> (left-to-right)

f has to extract the key and value. Value must be mergable.

Attention: if the key is not unique, the earliest value with the key will be in the map.

Error handling

type HasCallStack = ?callStack :: CallStack #

Request a CallStack.

NOTE: The implicit parameter ?callStack :: CallStack is an implementation detail and should not be considered part of the CallStack API, we may decide to change the implementation in the future.

Since: base-4.9.0.0

module Data.Error