| Safe Haskell | Safe-Inferred |
|---|---|
| Language | GHC2021 |
Internal.Prelude
Synopsis
- type String = [Char]
- data Bool
- data Char
- data Int
- data Maybe a
- class a ~# b => (a :: k0) ~~ (b :: k1)
- class a ~# b => (a :: k) ~ (b :: k)
- data Natural
- data Integer
- data IO a
- type Type = TYPE LiftedRep
- type Constraint = CONSTRAINT LiftedRep
- class Show a where
- class Functor f => Applicative (f :: Type -> Type) where
- class Functor (f :: Type -> Type) where
- fmap :: (a -> b) -> f a -> f b
- class Applicative m => Monad (m :: Type -> Type) where
- class Arbitrary a where
- newtype Fixed (a :: k) = MkFixed Integer
- class Generic a
- class Bounded a where
- class Enum a where
- class (Real a, Fractional a) => RealFrac a where
- class (Real a, Enum a) => Integral a where
- class Read a
- type family (a :: k) == (b :: k) :: Bool where ...
- class Eq a => Ord a where
- class Eq a where
- data ByteString
- data Map k a
- data Word32
- data Text
- data Either a b
- class Monad m => MonadThrow (m :: Type -> Type) where
- throwM :: (HasCallStack, Exception e) => e -> m a
- data SomeException = Exception e => SomeException e
- class (Typeable e, Show e) => Exception e
- class Monad m => MonadIO (m :: Type -> Type) where
- data Set a
- type HasCallStack = ?callStack :: CallStack
- class Num a where
- class TestEquality (f :: k -> Type) where
- testEquality :: forall (a :: k) (b :: k). f a -> f b -> Maybe (a :~: b)
- data (a :: k1) :~~: (b :: k2) where
- data (a :: k) :~: (b :: k) where
- newtype Min a = Min {
- getMin :: a
- newtype IdentityT (f :: k -> Type) (a :: k) = IdentityT {
- runIdentityT :: f a
- class (forall (m :: Type -> Type). Monad m => Monad (t m)) => MonadTrans (t :: (Type -> Type) -> Type -> Type) where
- data ReaderT r (m :: Type -> Type) a
- data Seq a
- data GenericArbitrary a
- class Monad m => MonadError e (m :: Type -> Type) | m -> e where
- throwError :: e -> m a
- ($) :: forall (r :: RuntimeRep) a (b :: TYPE r). (a -> b) -> a -> b
- otherwise :: Bool
- join :: Monad m => m (m a) -> m a
- (<>) :: Semigroup a => a -> a -> a
- toList :: Foldable t => t a -> [a]
- minimum :: (Foldable t, Ord a) => t a -> a
- foldMap :: (Foldable t, Monoid m) => (a -> m) -> t a -> m
- genericShrink :: (Generic a, RecursivelyShrink (Rep a), GSubterms (Rep a) a) => a -> [a]
- apply :: forall {k1} {k2} (f :: k1 -> k2) (g :: k1 -> k2) (a :: k1) (b :: k1). (f :~: g) -> (a :~: b) -> f a :~: g b
- fromIntegral :: (Integral a, Num b) => a -> b
- empty :: Alternative f => f a
- (<|>) :: Alternative f => f a -> f a -> f a
- filter :: (a -> Bool) -> [a] -> [a]
- bool :: a -> a -> Bool -> a
- when :: Applicative f => Bool -> f () -> f ()
- fromMaybe :: a -> Maybe a -> a
- catMaybes :: [Maybe a] -> [a]
- ($>) :: Functor f => f a -> b -> f b
- void :: Functor f => f a -> f ()
- unless :: Applicative f => Bool -> f () -> f ()
- id :: a -> a
- fail :: MonadFail m => String -> m a
- (<$>) :: Functor f => (a -> b) -> f a -> f b
- guard :: Alternative f => Bool -> f ()
- throwWithCallStack :: (HasCallStack, MonadThrow m, Exception e) => e -> m a
- checkpointCallStack :: (MonadCatch m, HasCallStack) => m a -> m a
- swap :: (a, b) -> (b, a)
- bimap :: Bifunctor p => (a -> b) -> (c -> d) -> p a c -> p b d
- (.) :: (b -> c) -> (a -> b) -> a -> c
- const :: a -> b -> a
- fst :: (a, b) -> a
- readMaybe :: Read a => String -> Maybe a
- uncurry :: (a -> b -> c) -> (a, b) -> c
- for :: (Traversable t, Applicative f) => t a -> (a -> f b) -> f (t b)
- concat :: Foldable t => t [a] -> [a]
- (>>>) :: forall {k} cat (a :: k) (b :: k) (c :: k). Category cat => cat a b -> cat b c -> cat a c
- (&&) :: Bool -> Bool -> Bool
- (||) :: Bool -> Bool -> Bool
- not :: Bool -> Bool
- (=<<) :: Monad m => (a -> m b) -> m a -> m b
- flip :: (a -> b -> c) -> b -> a -> c
- ($!) :: forall (r :: RuntimeRep) a (b :: TYPE r). (a -> b) -> a -> b
- maybe :: b -> (a -> b) -> Maybe a -> b
- isJust :: Maybe a -> Bool
- isNothing :: Maybe a -> Bool
- all :: Foldable t => (a -> Bool) -> t a -> Bool
- concatMap :: Foldable t => (a -> [b]) -> t a -> [b]
- (/) :: Fractional a => a -> a -> a
- snd :: (a, b) -> b
- (<&>) :: Functor f => f a -> (a -> b) -> f b
- (&) :: a -> (a -> b) -> b
- either :: (a -> c) -> (b -> c) -> Either a b -> c
- fromRight :: b -> Either a b -> b
- sym :: forall {k} (a :: k) (b :: k). (a :~: b) -> b :~: a
- trans :: forall {k} (a :: k) (b :: k) (c :: k). (a :~: b) -> (b :~: c) -> a :~: c
- castWith :: (a :~: b) -> a -> b
- gcastWith :: forall {k} (a :: k) (b :: k) r. (a :~: b) -> (a ~ b => r) -> r
- inner :: forall {k1} {k2} (f :: k1 -> k2) (a :: k1) (g :: k1 -> k2) (b :: k1). (f a :~: g b) -> a :~: b
- outer :: forall {k1} {k2} (f :: k1 -> k2) (a :: k1) (g :: k1 -> k2) (b :: k1). (f a :~: g b) -> f :~: g
- traverse_ :: (Foldable t, Applicative f) => (a -> f b) -> t a -> f ()
- for_ :: (Foldable t, Applicative f) => t a -> (a -> f b) -> f ()
- (>=>) :: Monad m => (a -> m b) -> (b -> m c) -> a -> m c
- (<=<) :: Monad m => (b -> m c) -> (a -> m b) -> a -> m c
- replicateM :: Applicative m => Int -> m a -> m [a]
- replicateM_ :: Applicative m => Int -> m a -> m ()
- nonEmpty :: [a] -> Maybe (NonEmpty a)
- genericArbitrary :: forall a (ga :: Type -> Type) (some :: Bool). (Generic a, GArbitrary a ga some, ga ~ Rep a) => Gen a
Documentation
Instances
The character type Char is an enumeration whose values represent
Unicode (or equivalently ISO/IEC 10646) code points (i.e. characters, see
http://www.unicode.org/ for details). This set extends the ISO 8859-1
(Latin-1) character set (the first 256 characters), which is itself an extension
of the ASCII character set (the first 128 characters). A character literal in
Haskell has type Char.
To convert a Char to or from the corresponding Int value defined
by Unicode, use toEnum and fromEnum from the
Enum class respectively (or equivalently ord and
chr).
Instances
A fixed-precision integer type with at least the range [-2^29 .. 2^29-1].
The exact range for a given implementation can be determined by using
minBound and maxBound from the Bounded class.
Instances
| Arbitrary Int | |
| CoArbitrary Int | |
Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Int -> Gen b -> Gen b # | |
| FromJSON Int | |
Defined in Data.Aeson.Types.FromJSON | |
| FromJSONKey Int | |
Defined in Data.Aeson.Types.FromJSON | |
| ToJSON Int | |
| ToJSONKey Int | |
Defined in Data.Aeson.Types.ToJSON | |
| Data Int | Since: base-4.0.0.0 |
Defined in Data.Data Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Int -> c Int # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c Int # dataTypeOf :: Int -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c Int) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c Int) # gmapT :: (forall b. Data b => b -> b) -> Int -> Int # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Int -> r # gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Int -> r # gmapQ :: (forall d. Data d => d -> u) -> Int -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> Int -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> Int -> m Int # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Int -> m Int # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Int -> m Int # | |
| Bounded Int | Since: base-2.1 |
| Enum Int | Since: base-2.1 |
| Num Int | Since: base-2.1 |
| Read Int | Since: base-2.1 |
| Integral Int | Since: base-2.0.1 |
| Real Int | Since: base-2.0.1 |
Defined in GHC.Real Methods toRational :: Int -> Rational # | |
| Show Int | Since: base-2.1 |
| Subtractive Int | |
Defined in Basement.Numerical.Subtractive Associated Types type Difference Int # | |
| PrimMemoryComparable Int | |
Defined in Basement.PrimType | |
| PrimType Int | |
Defined in Basement.PrimType Methods primSizeInBytes :: Proxy Int -> CountOf Word8 # primShiftToBytes :: Proxy Int -> Int # primBaUIndex :: ByteArray# -> Offset Int -> Int # primMbaURead :: PrimMonad prim => MutableByteArray# (PrimState prim) -> Offset Int -> prim Int # primMbaUWrite :: PrimMonad prim => MutableByteArray# (PrimState prim) -> Offset Int -> Int -> prim () # primAddrIndex :: Addr# -> Offset Int -> Int # primAddrRead :: PrimMonad prim => Addr# -> Offset Int -> prim Int # primAddrWrite :: PrimMonad prim => Addr# -> Offset Int -> Int -> prim () # | |
| Default Int | |
Defined in Data.Default.Class | |
| NFData Int | |
Defined in Control.DeepSeq | |
| Eq Int | |
| Ord Int | |
| Hashable Int | |
Defined in Data.Hashable.Class | |
| PersistField Int | |
Defined in Database.Persist.Class.PersistField | |
| Uniform Int | |
Defined in System.Random.Internal Methods uniformM :: StatefulGen g m => g -> m Int # | |
| UniformRange Int | |
Defined in System.Random.Internal | |
| ByteSource Int | |
Defined in Data.UUID.Types.Internal.Builder | |
| Unbox Int | |
Defined in Data.Vector.Unboxed.Base | |
| Lift Int | |
| Vector Vector Int | |
Defined in Data.Vector.Unboxed.Base Methods basicUnsafeFreeze :: Mutable Vector s Int -> ST s (Vector Int) # basicUnsafeThaw :: Vector Int -> ST s (Mutable Vector s Int) # basicLength :: Vector Int -> Int # basicUnsafeSlice :: Int -> Int -> Vector Int -> Vector Int # basicUnsafeIndexM :: Vector Int -> Int -> Box Int # basicUnsafeCopy :: Mutable Vector s Int -> Vector Int -> ST s () # | |
| MVector MVector Int | |
Defined in Data.Vector.Unboxed.Base Methods basicLength :: MVector s Int -> Int # basicUnsafeSlice :: Int -> Int -> MVector s Int -> MVector s Int # basicOverlaps :: MVector s Int -> MVector s Int -> Bool # basicUnsafeNew :: Int -> ST s (MVector s Int) # basicInitialize :: MVector s Int -> ST s () # basicUnsafeReplicate :: Int -> Int -> ST s (MVector s Int) # basicUnsafeRead :: MVector s Int -> Int -> ST s Int # basicUnsafeWrite :: MVector s Int -> Int -> Int -> ST s () # basicClear :: MVector s Int -> ST s () # basicSet :: MVector s Int -> Int -> ST s () # basicUnsafeCopy :: MVector s Int -> MVector s Int -> ST s () # basicUnsafeMove :: MVector s Int -> MVector s Int -> ST s () # basicUnsafeGrow :: MVector s Int -> Int -> ST s (MVector s Int) # | |
| Generic1 (URec Int :: k -> Type) | |
| Foldable (UInt :: Type -> Type) | Since: base-4.9.0.0 |
Defined in Data.Foldable Methods fold :: Monoid m => UInt m -> m # foldMap :: Monoid m => (a -> m) -> UInt a -> m # foldMap' :: Monoid m => (a -> m) -> UInt a -> m # foldr :: (a -> b -> b) -> b -> UInt a -> b # foldr' :: (a -> b -> b) -> b -> UInt a -> b # foldl :: (b -> a -> b) -> b -> UInt a -> b # foldl' :: (b -> a -> b) -> b -> UInt a -> b # foldr1 :: (a -> a -> a) -> UInt a -> a # foldl1 :: (a -> a -> a) -> UInt a -> a # elem :: Eq a => a -> UInt a -> Bool # maximum :: Ord a => UInt a -> a # | |
| Traversable (UInt :: Type -> Type) | Since: base-4.9.0.0 |
| Functor (URec Int :: Type -> Type) | Since: base-4.9.0.0 |
| Generic (URec Int p) | |
| Show (URec Int p) | Since: base-4.9.0.0 |
| Eq (URec Int p) | Since: base-4.9.0.0 |
| Ord (URec Int p) | Since: base-4.9.0.0 |
| type NatNumMaxBound Int | |
Defined in Basement.Nat | |
| type Difference Int | |
Defined in Basement.Numerical.Subtractive | |
| type PrimSize Int | |
Defined in Basement.PrimType | |
| newtype Vector Int | |
| data URec Int (p :: k) | Used for marking occurrences of Since: base-4.9.0.0 |
| type ByteSink Int g | |
Defined in Data.UUID.Types.Internal.Builder type ByteSink Int g = Takes4Bytes g | |
| newtype MVector s Int | |
| type Rep1 (URec Int :: k -> Type) | Since: base-4.9.0.0 |
Defined in GHC.Generics | |
| type Rep (URec Int p) | Since: base-4.9.0.0 |
Defined in GHC.Generics | |
The Maybe type encapsulates an optional value. A value of type
Maybe aa (represented as Just aNothing). Using Maybe is a good way to
deal with errors or exceptional cases without resorting to drastic
measures such as error.
The Maybe type is also a monad. It is a simple kind of error
monad, where all errors are represented by Nothing. A richer
error monad can be built using the Either type.
Instances
| Arbitrary1 Maybe | |
Defined in Test.QuickCheck.Arbitrary | |
| FromJSON1 Maybe | |
Defined in Data.Aeson.Types.FromJSON | |
| ToJSON1 Maybe | |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON :: (a -> Bool) -> (a -> Value) -> ([a] -> Value) -> Maybe a -> Value # liftToJSONList :: (a -> Bool) -> (a -> Value) -> ([a] -> Value) -> [Maybe a] -> Value # liftToEncoding :: (a -> Bool) -> (a -> Encoding) -> ([a] -> Encoding) -> Maybe a -> Encoding # liftToEncodingList :: (a -> Bool) -> (a -> Encoding) -> ([a] -> Encoding) -> [Maybe a] -> Encoding # liftOmitField :: (a -> Bool) -> Maybe a -> Bool # | |
| MonadFail Maybe | Since: base-4.9.0.0 |
Defined in Control.Monad.Fail | |
| Foldable Maybe | Since: base-2.1 |
Defined in Data.Foldable Methods fold :: Monoid m => Maybe m -> m # foldMap :: Monoid m => (a -> m) -> Maybe a -> m # foldMap' :: Monoid m => (a -> m) -> Maybe a -> m # foldr :: (a -> b -> b) -> b -> Maybe a -> b # foldr' :: (a -> b -> b) -> b -> Maybe a -> b # foldl :: (b -> a -> b) -> b -> Maybe a -> b # foldl' :: (b -> a -> b) -> b -> Maybe a -> b # foldr1 :: (a -> a -> a) -> Maybe a -> a # foldl1 :: (a -> a -> a) -> Maybe a -> a # elem :: Eq a => a -> Maybe a -> Bool # maximum :: Ord a => Maybe a -> a # minimum :: Ord a => Maybe a -> a # | |
| Traversable Maybe | Since: base-2.1 |
| Alternative Maybe | Picks the leftmost Since: base-2.1 |
| Applicative Maybe | Since: base-2.1 |
| Functor Maybe | Since: base-2.1 |
| Monad Maybe | Since: base-2.1 |
| MonadPlus Maybe | Picks the leftmost Since: base-2.1 |
| MonadFailure Maybe | |
| NFData1 Maybe | Since: deepseq-1.4.3.0 |
Defined in Control.DeepSeq | |
| MonadThrow Maybe | |
Defined in Control.Monad.Catch Methods throwM :: (HasCallStack, Exception e) => e -> Maybe a # | |
| Hashable1 Maybe | |
Defined in Data.Hashable.Class | |
| Generic1 Maybe | |
| MonadBaseControl Maybe Maybe | |
| MonadError () Maybe | Since: mtl-2.2.2 |
Defined in Control.Monad.Error.Class | |
| Lift a => Lift (Maybe a :: Type) | |
| Arbitrary a => Arbitrary (Maybe a) | |
| CoArbitrary a => CoArbitrary (Maybe a) | |
Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Maybe a -> Gen b -> Gen b # | |
| FromJSON a => FromJSON (Maybe a) | |
Defined in Data.Aeson.Types.FromJSON | |
| ToJSON a => ToJSON (Maybe a) | |
| Data a => Data (Maybe a) | Since: base-4.0.0.0 |
Defined in Data.Data Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Maybe a -> c (Maybe a) # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Maybe a) # toConstr :: Maybe a -> Constr # dataTypeOf :: Maybe a -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Maybe a)) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Maybe a)) # gmapT :: (forall b. Data b => b -> b) -> Maybe a -> Maybe a # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Maybe a -> r # gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Maybe a -> r # gmapQ :: (forall d. Data d => d -> u) -> Maybe a -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> Maybe a -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> Maybe a -> m (Maybe a) # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Maybe a -> m (Maybe a) # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Maybe a -> m (Maybe a) # | |
| Semigroup a => Monoid (Maybe a) | Lift a semigroup into Since 4.11.0: constraint on inner Since: base-2.1 |
| Semigroup a => Semigroup (Maybe a) | Since: base-4.9.0.0 |
| Generic (Maybe a) | |
| SingKind a => SingKind (Maybe a) | Since: base-4.9.0.0 |
Defined in GHC.Generics Associated Types type DemoteRep (Maybe a) | |
| Read a => Read (Maybe a) | Since: base-2.1 |
| Show a => Show (Maybe a) | Since: base-2.1 |
| Default (Maybe a) | |
Defined in Data.Default.Class | |
| NFData a => NFData (Maybe a) | |
Defined in Control.DeepSeq | |
| Eq a => Eq (Maybe a) | Since: base-2.1 |
| Ord a => Ord (Maybe a) | Since: base-2.1 |
| Hashable a => Hashable (Maybe a) | |
Defined in Data.Hashable.Class | |
| MonoFoldable (Maybe a) | |
Defined in Data.MonoTraversable Methods ofoldMap :: Monoid m => (Element (Maybe a) -> m) -> Maybe a -> m # ofoldr :: (Element (Maybe a) -> b -> b) -> b -> Maybe a -> b # ofoldl' :: (a0 -> Element (Maybe a) -> a0) -> a0 -> Maybe a -> a0 # otoList :: Maybe a -> [Element (Maybe a)] # oall :: (Element (Maybe a) -> Bool) -> Maybe a -> Bool # oany :: (Element (Maybe a) -> Bool) -> Maybe a -> Bool # olength64 :: Maybe a -> Int64 # ocompareLength :: Integral i => Maybe a -> i -> Ordering # otraverse_ :: Applicative f => (Element (Maybe a) -> f b) -> Maybe a -> f () # ofor_ :: Applicative f => Maybe a -> (Element (Maybe a) -> f b) -> f () # omapM_ :: Applicative m => (Element (Maybe a) -> m ()) -> Maybe a -> m () # oforM_ :: Applicative m => Maybe a -> (Element (Maybe a) -> m ()) -> m () # ofoldlM :: Monad m => (a0 -> Element (Maybe a) -> m a0) -> a0 -> Maybe a -> m a0 # ofoldMap1Ex :: Semigroup m => (Element (Maybe a) -> m) -> Maybe a -> m # ofoldr1Ex :: (Element (Maybe a) -> Element (Maybe a) -> Element (Maybe a)) -> Maybe a -> Element (Maybe a) # ofoldl1Ex' :: (Element (Maybe a) -> Element (Maybe a) -> Element (Maybe a)) -> Maybe a -> Element (Maybe a) # headEx :: Maybe a -> Element (Maybe a) # lastEx :: Maybe a -> Element (Maybe a) # unsafeHead :: Maybe a -> Element (Maybe a) # unsafeLast :: Maybe a -> Element (Maybe a) # maximumByEx :: (Element (Maybe a) -> Element (Maybe a) -> Ordering) -> Maybe a -> Element (Maybe a) # minimumByEx :: (Element (Maybe a) -> Element (Maybe a) -> Ordering) -> Maybe a -> Element (Maybe a) # | |
| MonoFunctor (Maybe a) | |
| MonoPointed (Maybe a) | |
| MonoTraversable (Maybe a) | |
| PersistField a => PersistField (Maybe a) | |
Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Maybe a -> PersistValue # fromPersistValue :: PersistValue -> Either Text (Maybe a) # | |
| SingI ('Nothing :: Maybe a) | Since: base-4.9.0.0 |
Defined in GHC.Generics | |
| SingI a2 => SingI ('Just a2 :: Maybe a1) | Since: base-4.9.0.0 |
Defined in GHC.Generics | |
| type Failure Maybe | |
Defined in Basement.Monad | |
| type Rep1 Maybe | Since: base-4.6.0.0 |
| type StM Maybe a | |
Defined in Control.Monad.Trans.Control | |
| type DemoteRep (Maybe a) | |
Defined in GHC.Generics | |
| type Rep (Maybe a) | Since: base-4.6.0.0 |
Defined in GHC.Generics | |
| data Sing (b :: Maybe a) | |
| type Element (Maybe a) | |
Defined in Data.MonoTraversable | |
class a ~# b => (a :: k0) ~~ (b :: k1) infix 4 #
Lifted, heterogeneous equality. By lifted, we mean that it
can be bogus (deferred type error). By heterogeneous, the two
types a and b might have different kinds. Because ~~ can
appear unexpectedly in error messages to users who do not care
about the difference between heterogeneous equality ~~ and
homogeneous equality ~, this is printed as ~ unless
-fprint-equality-relations is set.
In 0.7.0, the fixity was set to infix 4 to match the fixity of :~~:.
class a ~# b => (a :: k) ~ (b :: k) infix 4 #
Lifted, homogeneous equality. By lifted, we mean that it
can be bogus (deferred type error). By homogeneous, the two
types a and b must have the same kinds.
Natural number
Invariant: numbers <= 0xffffffffffffffff use the NS constructor
Instances
| FromJSON Natural | |
Defined in Data.Aeson.Types.FromJSON | |
| FromJSONKey Natural | |
Defined in Data.Aeson.Types.FromJSON Methods | |
| ToJSON Natural | |
| ToJSONKey Natural | |
Defined in Data.Aeson.Types.ToJSON | |
| Data Natural | Since: base-4.8.0.0 |
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 |
| Num Natural | Note that Since: base-4.8.0.0 |
| Read Natural | Since: base-4.8.0.0 |
| Integral Natural | Since: base-4.8.0.0 |
Defined in GHC.Real | |
| Real Natural | Since: base-4.8.0.0 |
Defined in GHC.Real Methods toRational :: Natural -> Rational # | |
| Show Natural | Since: base-4.8.0.0 |
| Subtractive Natural | |
Defined in Basement.Numerical.Subtractive Associated Types type Difference Natural # | |
| NFData Natural | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
| Eq Natural | |
| Ord Natural | |
| Hashable Natural | |
Defined in Data.Hashable.Class | |
| (TypeError ((((('Text "The instance of PersistField for the Natural type was removed." ':$$: 'Text "Please see the documentation for OverflowNatural if you want to ") ':$$: 'Text "continue using the old behavior or want to see documentation on ") ':$$: 'Text "why the instance was removed.") ':$$: 'Text "") ':$$: 'Text "This error instance will be removed in a future release.") :: Constraint) => PersistField Natural | |
Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Natural -> PersistValue # | |
| UniformRange Natural | |
Defined in System.Random.Internal | |
| KnownNat n => HasResolution (n :: Nat) | For example, |
Defined in Data.Fixed Methods resolution :: p n -> Integer # | |
| TestCoercion SNat | Since: base-4.18.0.0 |
Defined in GHC.TypeNats | |
| TestEquality SNat | Since: base-4.18.0.0 |
Defined in GHC.TypeNats | |
| Lift Natural | |
| type Difference Natural | |
Defined in Basement.Numerical.Subtractive | |
| type Compare (a :: Natural) (b :: Natural) | |
Defined in Data.Type.Ord | |
Arbitrary precision integers. In contrast with fixed-size integral types
such as Int, the Integer type represents the entire infinite range of
integers.
Integers are stored in a kind of sign-magnitude form, hence do not expect two's complement form when using bit operations.
If the value is small (fit into an Int), IS constructor is used.
Otherwise Integer and IN constructors are used to store a BigNat
representing respectively the positive or the negative value magnitude.
Invariant: Integer and IN are used iff value doesn't fit in IS
Instances
| Arbitrary Integer | |
| CoArbitrary Integer | |
Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Integer -> Gen b -> Gen b # | |
| FromJSON Integer | This instance includes a bounds check to prevent maliciously
large inputs to fill up the memory of the target system. You can
newtype |
Defined in Data.Aeson.Types.FromJSON | |
| FromJSONKey Integer | |
Defined in Data.Aeson.Types.FromJSON Methods | |
| ToJSON Integer | |
| ToJSONKey Integer | |
Defined in Data.Aeson.Types.ToJSON | |
| Data Integer | Since: base-4.0.0.0 |
Defined in Data.Data Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Integer -> c Integer # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c Integer # toConstr :: Integer -> Constr # dataTypeOf :: Integer -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c Integer) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c Integer) # gmapT :: (forall b. Data b => b -> b) -> Integer -> Integer # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Integer -> r # gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Integer -> r # gmapQ :: (forall d. Data d => d -> u) -> Integer -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> Integer -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> Integer -> m Integer # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Integer -> m Integer # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Integer -> m Integer # | |
| Enum Integer | Since: base-2.1 |
| Num Integer | Since: base-2.1 |
| Read Integer | Since: base-2.1 |
| Integral Integer | Since: base-2.0.1 |
Defined in GHC.Real | |
| Real Integer | Since: base-2.0.1 |
Defined in GHC.Real Methods toRational :: Integer -> Rational # | |
| Show Integer | Since: base-2.1 |
| Subtractive Integer | |
Defined in Basement.Numerical.Subtractive Associated Types type Difference Integer # | |
| Default Integer | |
Defined in Data.Default.Class | |
| NFData Integer | |
Defined in Control.DeepSeq | |
| Eq Integer | |
| Ord Integer | |
| Hashable Integer | |
Defined in Data.Hashable.Class | |
| PersistField Rational | |
Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Rational -> PersistValue # | |
| UniformRange Integer | |
Defined in System.Random.Internal | |
| Lift Integer | |
| type Difference Integer | |
Defined in Basement.Numerical.Subtractive | |
A value of type IO aa.
There is really only one way to "perform" an I/O action: bind it to
Main.main in your program. When your program is run, the I/O will
be performed. It isn't possible to perform I/O from an arbitrary
function, unless that function is itself in the IO monad and called
at some point, directly or indirectly, from Main.main.
IO is a monad, so IO actions can be combined using either the do-notation
or the >> and >>= operations from the Monad
class.
Instances
type Constraint = CONSTRAINT LiftedRep #
The kind of lifted constraints
Conversion of values to readable Strings.
Derived instances of Show have the following properties, which
are compatible with derived instances of Read:
- The result of
showis a syntactically correct Haskell expression containing only constants, given the fixity declarations in force at the point where the type is declared. It contains only the constructor names defined in the data type, parentheses, and spaces. When labelled constructor fields are used, braces, commas, field names, and equal signs are also used. - If the constructor is defined to be an infix operator, then
showsPrecwill produce infix applications of the constructor. - the representation will be enclosed in parentheses if the
precedence of the top-level constructor in
xis less thand(associativity is ignored). Thus, ifdis0then the result is never surrounded in parentheses; ifdis11it is always surrounded in parentheses, unless it is an atomic expression. - If the constructor is defined using record syntax, then
showwill produce the record-syntax form, with the fields given in the same order as the original declaration.
For example, given the declarations
infixr 5 :^: data Tree a = Leaf a | Tree a :^: Tree a
the derived instance of Show is equivalent to
instance (Show a) => Show (Tree a) where
showsPrec d (Leaf m) = showParen (d > app_prec) $
showString "Leaf " . showsPrec (app_prec+1) m
where app_prec = 10
showsPrec d (u :^: v) = showParen (d > up_prec) $
showsPrec (up_prec+1) u .
showString " :^: " .
showsPrec (up_prec+1) v
where up_prec = 5Note that right-associativity of :^: is ignored. For example,
show(Leaf 1 :^: Leaf 2 :^: Leaf 3)"Leaf 1 :^: (Leaf 2 :^: Leaf 3)".
Methods
Instances
class Functor f => Applicative (f :: Type -> Type) where #
A functor with application, providing operations to
A minimal complete definition must include implementations of pure
and of either <*> or liftA2. If it defines both, then they must behave
the same as their default definitions:
(<*>) =liftA2id
liftA2f x y = f<$>x<*>y
Further, any definition must satisfy the following:
- Identity
pureid<*>v = v- Composition
pure(.)<*>u<*>v<*>w = u<*>(v<*>w)- Homomorphism
puref<*>purex =pure(f x)- Interchange
u
<*>purey =pure($y)<*>u
The other methods have the following default definitions, which may be overridden with equivalent specialized implementations:
As a consequence of these laws, the Functor instance for f will satisfy
It may be useful to note that supposing
forall x y. p (q x y) = f x . g y
it follows from the above that
liftA2p (liftA2q u v) =liftA2f u .liftA2g v
If f is also a Monad, it should satisfy
(which implies that pure and <*> satisfy the applicative functor laws).
Methods
Lift a value.
(<*>) :: f (a -> b) -> f a -> f b infixl 4 #
Sequential application.
A few functors support an implementation of <*> that is more
efficient than the default one.
Example
Used in combination with (, <$>)( can be used to build a record.<*>)
>>>data MyState = MyState {arg1 :: Foo, arg2 :: Bar, arg3 :: Baz}
>>>produceFoo :: Applicative f => f Foo
>>>produceBar :: Applicative f => f Bar>>>produceBaz :: Applicative f => f Baz
>>>mkState :: Applicative f => f MyState>>>mkState = MyState <$> produceFoo <*> produceBar <*> produceBaz
liftA2 :: (a -> b -> c) -> f a -> f b -> f c #
Lift a binary function to actions.
Some functors support an implementation of liftA2 that is more
efficient than the default one. In particular, if fmap is an
expensive operation, it is likely better to use liftA2 than to
fmap over the structure and then use <*>.
This became a typeclass method in 4.10.0.0. Prior to that, it was
a function defined in terms of <*> and fmap.
Example
>>>liftA2 (,) (Just 3) (Just 5)Just (3,5)
(*>) :: f a -> f b -> f b infixl 4 #
Sequence actions, discarding the value of the first argument.
Examples
If used in conjunction with the Applicative instance for Maybe,
you can chain Maybe computations, with a possible "early return"
in case of Nothing.
>>>Just 2 *> Just 3Just 3
>>>Nothing *> Just 3Nothing
Of course a more interesting use case would be to have effectful computations instead of just returning pure values.
>>>import Data.Char>>>import Text.ParserCombinators.ReadP>>>let p = string "my name is " *> munch1 isAlpha <* eof>>>readP_to_S p "my name is Simon"[("Simon","")]
(<*) :: f a -> f b -> f a infixl 4 #
Sequence actions, discarding the value of the second argument.
Instances
| Applicative Gen | |
| Applicative IResult | |
| Applicative Parser | |
| Applicative Result | |
| Applicative AnnotatedException | |
Defined in Control.Exception.Annotated Methods pure :: a -> AnnotatedException a # (<*>) :: AnnotatedException (a -> b) -> AnnotatedException a -> AnnotatedException b # liftA2 :: (a -> b -> c) -> AnnotatedException a -> AnnotatedException b -> AnnotatedException c # (*>) :: AnnotatedException a -> AnnotatedException b -> AnnotatedException b # (<*) :: AnnotatedException a -> AnnotatedException b -> AnnotatedException a # | |
| Applicative ZipList | f <$> ZipList xs1 <*> ... <*> ZipList xsN
= ZipList (zipWithN f xs1 ... xsN)where (\a b c -> stimes c [a, b]) <$> ZipList "abcd" <*> ZipList "567" <*> ZipList [1..]
= ZipList (zipWith3 (\a b c -> stimes c [a, b]) "abcd" "567" [1..])
= ZipList {getZipList = ["a5","b6b6","c7c7c7"]}Since: base-2.1 |
| Applicative Complex | Since: base-4.9.0.0 |
| Applicative Identity | Since: base-4.8.0.0 |
| Applicative First | Since: base-4.8.0.0 |
| Applicative Last | Since: base-4.8.0.0 |
| Applicative Down | Since: base-4.11.0.0 |
| Applicative First | Since: base-4.9.0.0 |
| Applicative Last | Since: base-4.9.0.0 |
| Applicative Max | Since: base-4.9.0.0 |
| Applicative Min | Since: base-4.9.0.0 |
| Applicative Dual | Since: base-4.8.0.0 |
| Applicative Product | Since: base-4.8.0.0 |
| Applicative Sum | Since: base-4.8.0.0 |
| Applicative NonEmpty | Since: base-4.9.0.0 |
| Applicative Par1 | Since: base-4.9.0.0 |
| Applicative P | Since: base-4.5.0.0 |
| Applicative ReadP | Since: base-4.6.0.0 |
| Applicative ReadPrec | Since: base-4.6.0.0 |
| Applicative Seq | Since: containers-0.5.4 |
| Applicative Tree | |
| Applicative CryptoFailable | |
Defined in Crypto.Error.Types Methods pure :: a -> CryptoFailable a # (<*>) :: CryptoFailable (a -> b) -> CryptoFailable a -> CryptoFailable b # liftA2 :: (a -> b -> c) -> CryptoFailable a -> CryptoFailable b -> CryptoFailable c # (*>) :: CryptoFailable a -> CryptoFailable b -> CryptoFailable b # (<*) :: CryptoFailable a -> CryptoFailable b -> CryptoFailable a # | |
| Applicative CryptoFailable | |
Defined in Crypto.Error.Types Methods pure :: a -> CryptoFailable a # (<*>) :: CryptoFailable (a -> b) -> CryptoFailable a -> CryptoFailable b # liftA2 :: (a -> b -> c) -> CryptoFailable a -> CryptoFailable b -> CryptoFailable c # (*>) :: CryptoFailable a -> CryptoFailable b -> CryptoFailable b # (<*) :: CryptoFailable a -> CryptoFailable b -> CryptoFailable a # | |
| Applicative DNonEmpty | |
Defined in Data.DList.DNonEmpty.Internal | |
| Applicative DList | |
| Applicative IO | Since: base-2.1 |
| Applicative Array | |
| Applicative SmallArray | |
Defined in Data.Primitive.SmallArray Methods pure :: a -> SmallArray a # (<*>) :: SmallArray (a -> b) -> SmallArray a -> SmallArray b # liftA2 :: (a -> b -> c) -> SmallArray a -> SmallArray b -> SmallArray c # (*>) :: SmallArray a -> SmallArray b -> SmallArray b # (<*) :: SmallArray a -> SmallArray b -> SmallArray a # | |
| Applicative Q | |
| Applicative Flat | |
| Applicative FlatApp | |
| Applicative Vector | |
| Applicative Stream | |
| Applicative Maybe | Since: base-2.1 |
| Applicative Solo | Since: base-4.15 |
| Applicative List | Since: base-2.1 |
| Applicative (Parser i) | |
| Monad m => Applicative (WrappedMonad m) | Since: base-2.1 |
Defined in Control.Applicative Methods pure :: a -> WrappedMonad m a # (<*>) :: WrappedMonad m (a -> b) -> WrappedMonad m a -> WrappedMonad m b # liftA2 :: (a -> b -> c) -> WrappedMonad m a -> WrappedMonad m b -> WrappedMonad m c # (*>) :: WrappedMonad m a -> WrappedMonad m b -> WrappedMonad m b # (<*) :: WrappedMonad m a -> WrappedMonad m b -> WrappedMonad m a # | |
| Arrow a => Applicative (ArrowMonad a) | Since: base-4.6.0.0 |
Defined in Control.Arrow Methods pure :: a0 -> ArrowMonad a a0 # (<*>) :: ArrowMonad a (a0 -> b) -> ArrowMonad a a0 -> ArrowMonad a b # liftA2 :: (a0 -> b -> c) -> ArrowMonad a a0 -> ArrowMonad a b -> ArrowMonad a c # (*>) :: ArrowMonad a a0 -> ArrowMonad a b -> ArrowMonad a b # (<*) :: ArrowMonad a a0 -> ArrowMonad a b -> ArrowMonad a a0 # | |
| Applicative (Either e) | Since: base-3.0 |
| Applicative (U1 :: Type -> Type) | Since: base-4.9.0.0 |
| Applicative (Base64 k) | |
| Monad m => Applicative (ZipSource m) | |
Defined in Data.Conduit.Internal.Conduit | |
| DRG gen => Applicative (MonadPseudoRandom gen) | |
Defined in Crypto.Random.Types Methods pure :: a -> MonadPseudoRandom gen a # (<*>) :: MonadPseudoRandom gen (a -> b) -> MonadPseudoRandom gen a -> MonadPseudoRandom gen b # liftA2 :: (a -> b -> c) -> MonadPseudoRandom gen a -> MonadPseudoRandom gen b -> MonadPseudoRandom gen c # (*>) :: MonadPseudoRandom gen a -> MonadPseudoRandom gen b -> MonadPseudoRandom gen b # (<*) :: MonadPseudoRandom gen a -> MonadPseudoRandom gen b -> MonadPseudoRandom gen a # | |
| Applicative m => Applicative (LoggingT m) | |
Defined in Control.Monad.Logger | |
| Applicative m => Applicative (NoLoggingT m) | |
Defined in Control.Monad.Logger Methods pure :: a -> NoLoggingT m a # (<*>) :: NoLoggingT m (a -> b) -> NoLoggingT m a -> NoLoggingT m b # liftA2 :: (a -> b -> c) -> NoLoggingT m a -> NoLoggingT m b -> NoLoggingT m c # (*>) :: NoLoggingT m a -> NoLoggingT m b -> NoLoggingT m b # (<*) :: NoLoggingT m a -> NoLoggingT m b -> NoLoggingT m a # | |
| Applicative m => Applicative (WriterLoggingT m) | |
Defined in Control.Monad.Logger Methods pure :: a -> WriterLoggingT m a # (<*>) :: WriterLoggingT m (a -> b) -> WriterLoggingT m a -> WriterLoggingT m b # liftA2 :: (a -> b -> c) -> WriterLoggingT m a -> WriterLoggingT m b -> WriterLoggingT m c # (*>) :: WriterLoggingT m a -> WriterLoggingT m b -> WriterLoggingT m b # (<*) :: WriterLoggingT m a -> WriterLoggingT m b -> WriterLoggingT m a # | |
| Applicative f => Applicative (WrappedPoly f) | |
Defined in Data.MonoTraversable Methods pure :: a -> WrappedPoly f a # (<*>) :: WrappedPoly f (a -> b) -> WrappedPoly f a -> WrappedPoly f b # liftA2 :: (a -> b -> c) -> WrappedPoly f a -> WrappedPoly f b -> WrappedPoly f c # (*>) :: WrappedPoly f a -> WrappedPoly f b -> WrappedPoly f b # (<*) :: WrappedPoly f a -> WrappedPoly f b -> WrappedPoly f a # | |
| Applicative m => Applicative (ResourceT m) | |
Defined in Control.Monad.Trans.Resource.Internal | |
| Semigroup a => Applicative (These a) | |
| Semigroup a => Applicative (These a) | |
| (Functor m, Monad m) => Applicative (MaybeT m) | |
| MonadUnliftIO m => Applicative (Conc m) | Since: unliftio-0.2.9.0 |
| MonadUnliftIO m => Applicative (Concurrently m) | Since: unliftio-0.1.0.0 |
Defined in UnliftIO.Internals.Async Methods pure :: a -> Concurrently m a # (<*>) :: Concurrently m (a -> b) -> Concurrently m a -> Concurrently m b # liftA2 :: (a -> b -> c) -> Concurrently m a -> Concurrently m b -> Concurrently m c # (*>) :: Concurrently m a -> Concurrently m b -> Concurrently m b # (<*) :: Concurrently m a -> Concurrently m b -> Concurrently m a # | |
| Applicative (HandlerFor site) | |
Defined in Yesod.Core.Types Methods pure :: a -> HandlerFor site a # (<*>) :: HandlerFor site (a -> b) -> HandlerFor site a -> HandlerFor site b # liftA2 :: (a -> b -> c) -> HandlerFor site a -> HandlerFor site b -> HandlerFor site c # (*>) :: HandlerFor site a -> HandlerFor site b -> HandlerFor site b # (<*) :: HandlerFor site a -> HandlerFor site b -> HandlerFor site a # | |
| Applicative (WidgetFor site) | |
Defined in Yesod.Core.Types Methods pure :: a -> WidgetFor site a # (<*>) :: WidgetFor site (a -> b) -> WidgetFor site a -> WidgetFor site b # liftA2 :: (a -> b -> c) -> WidgetFor site a -> WidgetFor site b -> WidgetFor site c # (*>) :: WidgetFor site a -> WidgetFor site b -> WidgetFor site b # (<*) :: WidgetFor site a -> WidgetFor site b -> WidgetFor site a # | |
| Monoid a => Applicative ((,) a) | For tuples, the ("hello ", (+15)) <*> ("world!", 2002)
("hello world!",2017)Since: base-2.1 |
| Arrow a => Applicative (WrappedArrow a b) | Since: base-2.1 |
Defined in Control.Applicative Methods pure :: a0 -> WrappedArrow a b a0 # (<*>) :: WrappedArrow a b (a0 -> b0) -> WrappedArrow a b a0 -> WrappedArrow a b b0 # liftA2 :: (a0 -> b0 -> c) -> WrappedArrow a b a0 -> WrappedArrow a b b0 -> WrappedArrow a b c # (*>) :: WrappedArrow a b a0 -> WrappedArrow a b b0 -> WrappedArrow a b b0 # (<*) :: WrappedArrow a b a0 -> WrappedArrow a b b0 -> WrappedArrow a b a0 # | |
| Applicative m => Applicative (Kleisli m a) | Since: base-4.14.0.0 |
Defined in Control.Arrow | |
| Monoid m => Applicative (Const m :: Type -> Type) | Since: base-2.0.1 |
| Applicative f => Applicative (Ap f) | Since: base-4.12.0.0 |
| Applicative f => Applicative (Alt f) | Since: base-4.8.0.0 |
| (Generic1 f, Applicative (Rep1 f)) => Applicative (Generically1 f) | Since: base-4.17.0.0 |
Defined in GHC.Generics Methods pure :: a -> Generically1 f a # (<*>) :: Generically1 f (a -> b) -> Generically1 f a -> Generically1 f b # liftA2 :: (a -> b -> c) -> Generically1 f a -> Generically1 f b -> Generically1 f c # (*>) :: Generically1 f a -> Generically1 f b -> Generically1 f b # (<*) :: Generically1 f a -> Generically1 f b -> Generically1 f a # | |
| Applicative f => Applicative (Rec1 f) | Since: base-4.9.0.0 |
| Monad m => Applicative (ZipSink i m) | |
Defined in Data.Conduit.Internal.Conduit | |
| (Applicative f, Monad f) => Applicative (WhenMissing f x) | Equivalent to Since: containers-0.5.9 |
Defined in Data.IntMap.Internal Methods pure :: a -> WhenMissing f x a # (<*>) :: WhenMissing f x (a -> b) -> WhenMissing f x a -> WhenMissing f x b # liftA2 :: (a -> b -> c) -> WhenMissing f x a -> WhenMissing f x b -> WhenMissing f x c # (*>) :: WhenMissing f x a -> WhenMissing f x b -> WhenMissing f x b # (<*) :: WhenMissing f x a -> WhenMissing f x b -> WhenMissing f x a # | |
| Applicative (Tagged s) | |
| Applicative f => Applicative (Backwards f) | Apply |
Defined in Control.Applicative.Backwards | |
| (Monoid w, Functor m, Monad m) => Applicative (AccumT w m) | |
Defined in Control.Monad.Trans.Accum | |
| (Functor m, Monad m) => Applicative (ExceptT e m) | |
Defined in Control.Monad.Trans.Except | |
| Applicative m => Applicative (IdentityT m) | |
Defined in Control.Monad.Trans.Identity | |
| Applicative m => Applicative (ReaderT r m) | |
Defined in Control.Monad.Trans.Reader | |
| (Functor m, Monad m) => Applicative (SelectT r m) | |
Defined in Control.Monad.Trans.Select | |
| (Functor m, Monad m) => Applicative (StateT s m) | |
Defined in Control.Monad.Trans.State.Lazy | |
| (Functor m, Monad m) => Applicative (StateT s m) | |
Defined in Control.Monad.Trans.State.Strict | |
| (Functor m, Monad m) => Applicative (WriterT w m) | |
Defined in Control.Monad.Trans.Writer.CPS | |
| (Monoid w, Applicative m) => Applicative (WriterT w m) | |
Defined in Control.Monad.Trans.Writer.Lazy | |
| (Monoid w, Applicative m) => Applicative (WriterT w m) | |
Defined in Control.Monad.Trans.Writer.Strict | |
| Monoid a => Applicative (Constant a :: Type -> Type) | |
Defined in Data.Functor.Constant | |
| Applicative f => Applicative (Reverse f) | Derived instance. |
| Applicative (SubHandlerFor child master) | |
Defined in Yesod.Core.Types Methods pure :: a -> SubHandlerFor child master a # (<*>) :: SubHandlerFor child master (a -> b) -> SubHandlerFor child master a -> SubHandlerFor child master b # liftA2 :: (a -> b -> c) -> SubHandlerFor child master a -> SubHandlerFor child master b -> SubHandlerFor child master c # (*>) :: SubHandlerFor child master a -> SubHandlerFor child master b -> SubHandlerFor child master b # (<*) :: SubHandlerFor child master a -> SubHandlerFor child master b -> SubHandlerFor child master a # | |
| (Monoid a, Monoid b) => Applicative ((,,) a b) | Since: base-4.14.0.0 |
| (Applicative f, Applicative g) => Applicative (Product f g) | Since: base-4.9.0.0 |
Defined in Data.Functor.Product | |
| (Applicative f, Applicative g) => Applicative (f :*: g) | Since: base-4.9.0.0 |
| Monoid c => Applicative (K1 i c :: Type -> Type) | Since: base-4.12.0.0 |
| Applicative (ConduitT i o m) | |
Defined in Data.Conduit.Internal.Conduit Methods pure :: a -> ConduitT i o m a # (<*>) :: ConduitT i o m (a -> b) -> ConduitT i o m a -> ConduitT i o m b # liftA2 :: (a -> b -> c) -> ConduitT i o m a -> ConduitT i o m b -> ConduitT i o m c # (*>) :: ConduitT i o m a -> ConduitT i o m b -> ConduitT i o m b # (<*) :: ConduitT i o m a -> ConduitT i o m b -> ConduitT i o m a # | |
| Monad m => Applicative (ZipConduit i o m) | |
Defined in Data.Conduit.Internal.Conduit Methods pure :: a -> ZipConduit i o m a # (<*>) :: ZipConduit i o m (a -> b) -> ZipConduit i o m a -> ZipConduit i o m b # liftA2 :: (a -> b -> c) -> ZipConduit i o m a -> ZipConduit i o m b -> ZipConduit i o m c # (*>) :: ZipConduit i o m a -> ZipConduit i o m b -> ZipConduit i o m b # (<*) :: ZipConduit i o m a -> ZipConduit i o m b -> ZipConduit i o m a # | |
| (Monad f, Applicative f) => Applicative (WhenMatched f x y) | Equivalent to Since: containers-0.5.9 |
Defined in Data.IntMap.Internal Methods pure :: a -> WhenMatched f x y a # (<*>) :: WhenMatched f x y (a -> b) -> WhenMatched f x y a -> WhenMatched f x y b # liftA2 :: (a -> b -> c) -> WhenMatched f x y a -> WhenMatched f x y b -> WhenMatched f x y c # (*>) :: WhenMatched f x y a -> WhenMatched f x y b -> WhenMatched f x y b # (<*) :: WhenMatched f x y a -> WhenMatched f x y b -> WhenMatched f x y a # | |
| (Applicative f, Monad f) => Applicative (WhenMissing f k x) | Equivalent to Since: containers-0.5.9 |
Defined in Data.Map.Internal Methods pure :: a -> WhenMissing f k x a # (<*>) :: WhenMissing f k x (a -> b) -> WhenMissing f k x a -> WhenMissing f k x b # liftA2 :: (a -> b -> c) -> WhenMissing f k x a -> WhenMissing f k x b -> WhenMissing f k x c # (*>) :: WhenMissing f k x a -> WhenMissing f k x b -> WhenMissing f k x b # (<*) :: WhenMissing f k x a -> WhenMissing f k x b -> WhenMissing f k x a # | |
| Applicative (ContT r m) | |
Defined in Control.Monad.Trans.Cont | |
| (Monoid a, Monoid b, Monoid c) => Applicative ((,,,) a b c) | Since: base-4.14.0.0 |
Defined in GHC.Base | |
| Applicative ((->) r) | Since: base-2.1 |
| (Applicative f, Applicative g) => Applicative (Compose f g) | Since: base-4.9.0.0 |
Defined in Data.Functor.Compose | |
| (Applicative f, Applicative g) => Applicative (f :.: g) | Since: base-4.9.0.0 |
| Applicative f => Applicative (M1 i c f) | Since: base-4.9.0.0 |
| (Monad f, Applicative f) => Applicative (WhenMatched f k x y) | Equivalent to Since: containers-0.5.9 |
Defined in Data.Map.Internal Methods pure :: a -> WhenMatched f k x y a # (<*>) :: WhenMatched f k x y (a -> b) -> WhenMatched f k x y a -> WhenMatched f k x y b # liftA2 :: (a -> b -> c) -> WhenMatched f k x y a -> WhenMatched f k x y b -> WhenMatched f k x y c # (*>) :: WhenMatched f k x y a -> WhenMatched f k x y b -> WhenMatched f k x y b # (<*) :: WhenMatched f k x y a -> WhenMatched f k x y b -> WhenMatched f k x y a # | |
| (Functor m, Monad m) => Applicative (RWST r w s m) | |
Defined in Control.Monad.Trans.RWS.CPS | |
| (Monoid w, Functor m, Monad m) => Applicative (RWST r w s m) | |
Defined in Control.Monad.Trans.RWS.Lazy | |
| (Monoid w, Functor m, Monad m) => Applicative (RWST r w s m) | |
Defined in Control.Monad.Trans.RWS.Strict | |
| Monad state => Applicative (Builder collection mutCollection step state err) | |
Defined in Basement.MutableBuilder Methods pure :: a -> Builder collection mutCollection step state err a # (<*>) :: Builder collection mutCollection step state err (a -> b) -> Builder collection mutCollection step state err a -> Builder collection mutCollection step state err b # liftA2 :: (a -> b -> c) -> Builder collection mutCollection step state err a -> Builder collection mutCollection step state err b -> Builder collection mutCollection step state err c # (*>) :: Builder collection mutCollection step state err a -> Builder collection mutCollection step state err b -> Builder collection mutCollection step state err b # (<*) :: Builder collection mutCollection step state err a -> Builder collection mutCollection step state err b -> Builder collection mutCollection step state err a # | |
| Monad m => Applicative (Pipe l i o u m) | |
Defined in Data.Conduit.Internal.Pipe Methods pure :: a -> Pipe l i o u m a # (<*>) :: Pipe l i o u m (a -> b) -> Pipe l i o u m a -> Pipe l i o u m b # liftA2 :: (a -> b -> c) -> Pipe l i o u m a -> Pipe l i o u m b -> Pipe l i o u m c # (*>) :: Pipe l i o u m a -> Pipe l i o u m b -> Pipe l i o u m b # (<*) :: Pipe l i o u m a -> Pipe l i o u m b -> Pipe l i o u m a # | |
class Functor (f :: Type -> Type) where #
A type f is a Functor if it provides a function fmap which, given any types a and b
lets you apply any function from (a -> b) to turn an f a into an f b, preserving the
structure of f. Furthermore f needs to adhere to the following:
Note, that the second law follows from the free theorem of the type fmap and
the first law, so you need only check that the former condition holds.
See https://www.schoolofhaskell.com/user/edwardk/snippets/fmap or
https://github.com/quchen/articles/blob/master/second_functor_law.md
for an explanation.
Methods
fmap :: (a -> b) -> f a -> f b #
fmap is used to apply a function of type (a -> b) to a value of type f a,
where f is a functor, to produce a value of type f b.
Note that for any type constructor with more than one parameter (e.g., Either),
only the last type parameter can be modified with fmap (e.g., b in `Either a b`).
Some type constructors with two parameters or more have a Bifunctor
Examples
Convert from a Maybe IntMaybe String
using show:
>>>fmap show NothingNothing>>>fmap show (Just 3)Just "3"
Convert from an Either Int IntEither Int String using show:
>>>fmap show (Left 17)Left 17>>>fmap show (Right 17)Right "17"
Double each element of a list:
>>>fmap (*2) [1,2,3][2,4,6]
Apply even to the second element of a pair:
>>>fmap even (2,2)(2,True)
It may seem surprising that the function is only applied to the last element of the tuple
compared to the list example above which applies it to every element in the list.
To understand, remember that tuples are type constructors with multiple type parameters:
a tuple of 3 elements (a,b,c) can also be written (,,) a b c and its Functor instance
is defined for Functor ((,,) a b) (i.e., only the third parameter is free to be mapped over
with fmap).
It explains why fmap can be used with tuples containing values of different types as in the
following example:
>>>fmap even ("hello", 1.0, 4)("hello",1.0,True)
Instances
class Applicative m => Monad (m :: Type -> Type) where #
The Monad class defines the basic operations over a monad,
a concept from a branch of mathematics known as category theory.
From the perspective of a Haskell programmer, however, it is best to
think of a monad as an abstract datatype of actions.
Haskell's do expressions provide a convenient syntax for writing
monadic expressions.
Instances of Monad should satisfy the following:
- Left identity
returna>>=k = k a- Right identity
m>>=return= m- Associativity
m>>=(\x -> k x>>=h) = (m>>=k)>>=h
Furthermore, the Monad and Applicative operations should relate as follows:
The above laws imply:
and that pure and (<*>) satisfy the applicative functor laws.
The instances of Monad for lists, Maybe and IO
defined in the Prelude satisfy these laws.
Minimal complete definition
Methods
(>>=) :: m a -> (a -> m b) -> m b infixl 1 #
Sequentially compose two actions, passing any value produced by the first as an argument to the second.
'as ' can be understood as the >>= bsdo expression
do a <- as bs a
(>>) :: m a -> m b -> m b infixl 1 #
Sequentially compose two actions, discarding any value produced by the first, like sequencing operators (such as the semicolon) in imperative languages.
'as ' can be understood as the >> bsdo expression
do as bs
Inject a value into the monadic type.
Instances
| Monad Gen | |
| Monad IResult | |
| Monad Parser | |
| Monad Result | |
| Monad Complex | Since: base-4.9.0.0 |
| Monad Identity | Since: base-4.8.0.0 |
| Monad First | Since: base-4.8.0.0 |
| Monad Last | Since: base-4.8.0.0 |
| Monad Down | Since: base-4.11.0.0 |
| Monad First | Since: base-4.9.0.0 |
| Monad Last | Since: base-4.9.0.0 |
| Monad Max | Since: base-4.9.0.0 |
| Monad Min | Since: base-4.9.0.0 |
| Monad Dual | Since: base-4.8.0.0 |
| Monad Product | Since: base-4.8.0.0 |
| Monad Sum | Since: base-4.8.0.0 |
| Monad NonEmpty | Since: base-4.9.0.0 |
| Monad Par1 | Since: base-4.9.0.0 |
| Monad P | Since: base-2.1 |
| Monad ReadP | Since: base-2.1 |
| Monad ReadPrec | Since: base-2.1 |
| Monad Seq | |
| Monad Tree | |
| Monad CryptoFailable | |
Defined in Crypto.Error.Types Methods (>>=) :: CryptoFailable a -> (a -> CryptoFailable b) -> CryptoFailable b # (>>) :: CryptoFailable a -> CryptoFailable b -> CryptoFailable b # return :: a -> CryptoFailable a # | |
| Monad CryptoFailable | |
Defined in Crypto.Error.Types Methods (>>=) :: CryptoFailable a -> (a -> CryptoFailable b) -> CryptoFailable b # (>>) :: CryptoFailable a -> CryptoFailable b -> CryptoFailable b # return :: a -> CryptoFailable a # | |
| Monad DNonEmpty | |
| Monad DList | |
| Monad IO | Since: base-2.1 |
| Monad Array | |
| Monad SmallArray | |
Defined in Data.Primitive.SmallArray Methods (>>=) :: SmallArray a -> (a -> SmallArray b) -> SmallArray b # (>>) :: SmallArray a -> SmallArray b -> SmallArray b # return :: a -> SmallArray a # | |
| Monad Q | |
| Monad Vector | |
| Monad Stream | |
| Monad Maybe | Since: base-2.1 |
| Monad Solo | Since: base-4.15 |
| Monad List | Since: base-2.1 |
| Monad (Parser i) | |
| Monad m => Monad (WrappedMonad m) | Since: base-4.7.0.0 |
Defined in Control.Applicative Methods (>>=) :: WrappedMonad m a -> (a -> WrappedMonad m b) -> WrappedMonad m b # (>>) :: WrappedMonad m a -> WrappedMonad m b -> WrappedMonad m b # return :: a -> WrappedMonad m a # | |
| ArrowApply a => Monad (ArrowMonad a) | Since: base-2.1 |
Defined in Control.Arrow Methods (>>=) :: ArrowMonad a a0 -> (a0 -> ArrowMonad a b) -> ArrowMonad a b # (>>) :: ArrowMonad a a0 -> ArrowMonad a b -> ArrowMonad a b # return :: a0 -> ArrowMonad a a0 # | |
| Monad (Either e) | Since: base-4.4.0.0 |
| Monad (U1 :: Type -> Type) | Since: base-4.9.0.0 |
| Monad (Base64 k) | |
| DRG gen => Monad (MonadPseudoRandom gen) | |
Defined in Crypto.Random.Types Methods (>>=) :: MonadPseudoRandom gen a -> (a -> MonadPseudoRandom gen b) -> MonadPseudoRandom gen b # (>>) :: MonadPseudoRandom gen a -> MonadPseudoRandom gen b -> MonadPseudoRandom gen b # return :: a -> MonadPseudoRandom gen a # | |
| Monad m => Monad (LoggingT m) | |
| Monad m => Monad (NoLoggingT m) | |
Defined in Control.Monad.Logger Methods (>>=) :: NoLoggingT m a -> (a -> NoLoggingT m b) -> NoLoggingT m b # (>>) :: NoLoggingT m a -> NoLoggingT m b -> NoLoggingT m b # return :: a -> NoLoggingT m a # | |
| Monad m => Monad (WriterLoggingT m) | |
Defined in Control.Monad.Logger Methods (>>=) :: WriterLoggingT m a -> (a -> WriterLoggingT m b) -> WriterLoggingT m b # (>>) :: WriterLoggingT m a -> WriterLoggingT m b -> WriterLoggingT m b # return :: a -> WriterLoggingT m a # | |
| Monad f => Monad (WrappedPoly f) | |
Defined in Data.MonoTraversable Methods (>>=) :: WrappedPoly f a -> (a -> WrappedPoly f b) -> WrappedPoly f b # (>>) :: WrappedPoly f a -> WrappedPoly f b -> WrappedPoly f b # return :: a -> WrappedPoly f a # | |
| Monad m => Monad (ResourceT m) | |
| Semigroup a => Monad (These a) | |
| Semigroup a => Monad (These a) | |
| Monad m => Monad (MaybeT m) | |
| Monad (HandlerFor site) | |
Defined in Yesod.Core.Types Methods (>>=) :: HandlerFor site a -> (a -> HandlerFor site b) -> HandlerFor site b # (>>) :: HandlerFor site a -> HandlerFor site b -> HandlerFor site b # return :: a -> HandlerFor site a # | |
| Monad (WidgetFor site) | |
| Monoid a => Monad ((,) a) | Since: base-4.9.0.0 |
| Monad m => Monad (Kleisli m a) | Since: base-4.14.0.0 |
| Monad f => Monad (Ap f) | Since: base-4.12.0.0 |
| Monad f => Monad (Alt f) | Since: base-4.8.0.0 |
| Monad f => Monad (Rec1 f) | Since: base-4.9.0.0 |
| (Applicative f, Monad f) => Monad (WhenMissing f x) | Equivalent to Since: containers-0.5.9 |
Defined in Data.IntMap.Internal Methods (>>=) :: WhenMissing f x a -> (a -> WhenMissing f x b) -> WhenMissing f x b # (>>) :: WhenMissing f x a -> WhenMissing f x b -> WhenMissing f x b # return :: a -> WhenMissing f x a # | |
| Monad (Tagged s) | |
| (Monoid w, Functor m, Monad m) => Monad (AccumT w m) | |
| Monad m => Monad (ExceptT e m) | |
| Monad m => Monad (IdentityT m) | |
| Monad m => Monad (ReaderT r m) | |
| Monad m => Monad (SelectT r m) | |
| Monad m => Monad (StateT s m) | |
| Monad m => Monad (StateT s m) | |
| Monad m => Monad (WriterT w m) | |
| (Monoid w, Monad m) => Monad (WriterT w m) | |
| (Monoid w, Monad m) => Monad (WriterT w m) | |
| Monad m => Monad (Reverse m) | Derived instance. |
| Monad (SubHandlerFor child master) | |
Defined in Yesod.Core.Types Methods (>>=) :: SubHandlerFor child master a -> (a -> SubHandlerFor child master b) -> SubHandlerFor child master b # (>>) :: SubHandlerFor child master a -> SubHandlerFor child master b -> SubHandlerFor child master b # return :: a -> SubHandlerFor child master a # | |
| (Monoid a, Monoid b) => Monad ((,,) a b) | Since: base-4.14.0.0 |
| (Monad f, Monad g) => Monad (Product f g) | Since: base-4.9.0.0 |
| (Monad f, Monad g) => Monad (f :*: g) | Since: base-4.9.0.0 |
| Monad (ConduitT i o m) | |
| (Monad f, Applicative f) => Monad (WhenMatched f x y) | Equivalent to Since: containers-0.5.9 |
Defined in Data.IntMap.Internal Methods (>>=) :: WhenMatched f x y a -> (a -> WhenMatched f x y b) -> WhenMatched f x y b # (>>) :: WhenMatched f x y a -> WhenMatched f x y b -> WhenMatched f x y b # return :: a -> WhenMatched f x y a # | |
| (Applicative f, Monad f) => Monad (WhenMissing f k x) | Equivalent to Since: containers-0.5.9 |
Defined in Data.Map.Internal Methods (>>=) :: WhenMissing f k x a -> (a -> WhenMissing f k x b) -> WhenMissing f k x b # (>>) :: WhenMissing f k x a -> WhenMissing f k x b -> WhenMissing f k x b # return :: a -> WhenMissing f k x a # | |
| Monad (ContT r m) | |
| (Monoid a, Monoid b, Monoid c) => Monad ((,,,) a b c) | Since: base-4.14.0.0 |
| Monad ((->) r) | Since: base-2.1 |
| Monad f => Monad (M1 i c f) | Since: base-4.9.0.0 |
| (Monad f, Applicative f) => Monad (WhenMatched f k x y) | Equivalent to Since: containers-0.5.9 |
Defined in Data.Map.Internal Methods (>>=) :: WhenMatched f k x y a -> (a -> WhenMatched f k x y b) -> WhenMatched f k x y b # (>>) :: WhenMatched f k x y a -> WhenMatched f k x y b -> WhenMatched f k x y b # return :: a -> WhenMatched f k x y a # | |
| Monad m => Monad (RWST r w s m) | |
| (Monoid w, Monad m) => Monad (RWST r w s m) | |
| (Monoid w, Monad m) => Monad (RWST r w s m) | |
| Monad state => Monad (Builder collection mutCollection step state err) | |
Defined in Basement.MutableBuilder Methods (>>=) :: Builder collection mutCollection step state err a -> (a -> Builder collection mutCollection step state err b) -> Builder collection mutCollection step state err b # (>>) :: Builder collection mutCollection step state err a -> Builder collection mutCollection step state err b -> Builder collection mutCollection step state err b # return :: a -> Builder collection mutCollection step state err a # | |
| Monad m => Monad (Pipe l i o u m) | |
Random generation and shrinking of values.
QuickCheck provides Arbitrary instances for most types in base,
except those which incur extra dependencies.
For a wider range of Arbitrary instances see the
quickcheck-instances
package.
Minimal complete definition
Methods
A generator for values of the given type.
It is worth spending time thinking about what sort of test data
you want - good generators are often the difference between
finding bugs and not finding them. You can use sample,
label and classify to check the quality of your test data.
There is no generic arbitrary implementation included because we don't
know how to make a high-quality one. If you want one, consider using the
testing-feat or
generic-random packages.
The QuickCheck manual goes into detail on how to write good generators. Make sure to look at it, especially if your type is recursive!
Produces a (possibly) empty list of all the possible immediate shrinks of the given value.
The default implementation returns the empty list, so will not try to
shrink the value. If your data type has no special invariants, you can
enable shrinking by defining shrink = , but by customising
the behaviour of genericShrinkshrink you can often get simpler counterexamples.
Most implementations of shrink should try at least three things:
- Shrink a term to any of its immediate subterms.
You can use
subtermsto do this. - Recursively apply
shrinkto all immediate subterms. You can userecursivelyShrinkto do this. - Type-specific shrinkings such as replacing a constructor by a simpler constructor.
For example, suppose we have the following implementation of binary trees:
data Tree a = Nil | Branch a (Tree a) (Tree a)
We can then define shrink as follows:
shrink Nil = [] shrink (Branch x l r) = -- shrink Branch to Nil [Nil] ++ -- shrink to subterms [l, r] ++ -- recursively shrink subterms [Branch x' l' r' | (x', l', r') <- shrink (x, l, r)]
There are a couple of subtleties here:
- QuickCheck tries the shrinking candidates in the order they
appear in the list, so we put more aggressive shrinking steps
(such as replacing the whole tree by
Nil) before smaller ones (such as recursively shrinking the subtrees). - It is tempting to write the last line as
[Branch x' l' r' | x' <- shrink x, l' <- shrink l, r' <- shrink r]but this is the wrong thing! It will force QuickCheck to shrinkx,landrin tandem, and shrinking will stop once one of the three is fully shrunk.
There is a fair bit of boilerplate in the code above.
We can avoid it with the help of some generic functions.
The function genericShrink tries shrinking a term to all of its
subterms and, failing that, recursively shrinks the subterms.
Using it, we can define shrink as:
shrink x = shrinkToNil x ++ genericShrink x
where
shrinkToNil Nil = []
shrinkToNil (Branch _ l r) = [Nil]genericShrink is a combination of subterms, which shrinks
a term to any of its subterms, and recursivelyShrink, which shrinks
all subterms of a term. These may be useful if you need a bit more
control over shrinking than genericShrink gives you.
A final gotcha: we cannot define shrink as simply shrink x = Nil:genericShrink xNil to Nil, and shrinking will go into an
infinite loop.
If all this leaves you bewildered, you might try shrink = genericShrinkGeneric for your type. However, if your data type has any
special invariants, you will need to check that genericShrink can't break those invariants.
Instances
The type parameter should be an instance of HasResolution.
Instances
| NFData1 (Fixed :: Type -> Type) | Since: deepseq-1.4.3.0 |
Defined in Control.DeepSeq | |
| HasResolution a => Arbitrary (Fixed a) | |
| HasResolution a => CoArbitrary (Fixed a) | |
Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Fixed a -> Gen b -> Gen b # | |
| HasResolution a => FromJSON (Fixed a) | This instance includes a bounds check to prevent maliciously
large inputs to fill up the memory of the target system. You can
newtype |
Defined in Data.Aeson.Types.FromJSON | |
| HasResolution a => ToJSON (Fixed a) | |
| HasResolution a => ToJSONKey (Fixed a) | |
Defined in Data.Aeson.Types.ToJSON | |
| (Typeable k, Typeable a) => Data (Fixed a) | Since: base-4.1.0.0 |
Defined in Data.Fixed Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Fixed a -> c (Fixed a) # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Fixed a) # toConstr :: Fixed a -> Constr # dataTypeOf :: Fixed a -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Fixed a)) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Fixed a)) # gmapT :: (forall b. Data b => b -> b) -> Fixed a -> Fixed a # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Fixed a -> r # gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Fixed a -> r # gmapQ :: (forall d. Data d => d -> u) -> Fixed a -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> Fixed a -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> Fixed a -> m (Fixed a) # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Fixed a -> m (Fixed a) # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Fixed a -> m (Fixed a) # | |
| Enum (Fixed a) | Recall that, for numeric types, succ (0.000 :: Milli) == 0.001 and likewise pred (0.000 :: Milli) == -0.001 In other words, succ (0.000000000000 :: Pico) == 0.000000000001 and similarly pred (0.000000000000 :: Pico) == -0.000000000001 This is worth bearing in mind when defining [1..10] :: [Pico] evaluates to However, this is not true. On the contrary, similarly to the above
implementations of [1.000000000000, 1.00000000001, 1.00000000002, ..., 10.000000000000] and contains Since: base-2.1 |
| HasResolution a => Num (Fixed a) | Since: base-2.1 |
| HasResolution a => Read (Fixed a) | Since: base-4.3.0.0 |
| HasResolution a => Fractional (Fixed a) | Since: base-2.1 |
| HasResolution a => Real (Fixed a) | Since: base-2.1 |
Defined in Data.Fixed Methods toRational :: Fixed a -> Rational # | |
| HasResolution a => RealFrac (Fixed a) | Since: base-2.1 |
| HasResolution a => Show (Fixed a) | Since: base-2.1 |
| NFData (Fixed a) | Since: deepseq-1.3.0.0 |
Defined in Control.DeepSeq | |
| Eq (Fixed a) | Since: base-2.1 |
| Ord (Fixed a) | Since: base-2.1 |
| Hashable (Fixed a) | |
Defined in Data.Hashable.Class | |
| HasResolution a => PersistField (Fixed a) | |
Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Fixed a -> PersistValue # fromPersistValue :: PersistValue -> Either Text (Fixed 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.to≡idto.from≡id
Instances
The Bounded class is used to name the upper and lower limits of a
type. Ord is not a superclass of Bounded since types that are not
totally ordered may also have upper and lower bounds.
The Bounded class may be derived for any enumeration type;
minBound is the first constructor listed in the data declaration
and maxBound is the last.
Bounded may also be derived for single-constructor datatypes whose
constituent types are in Bounded.
Instances
| Bounded All | Since: base-2.1 |
| Bounded Any | Since: base-2.1 |
| Bounded CBool | |
| Bounded CChar | |
| Bounded CInt | |
| Bounded CIntMax | |
| Bounded CIntPtr | |
| Bounded CLLong | |
| Bounded CLong | |
| Bounded CPtrdiff | |
| Bounded CSChar | |
| Bounded CShort | |
| Bounded CSigAtomic | |
Defined in Foreign.C.Types | |
| Bounded CSize | |
| Bounded CUChar | |
| Bounded CUInt | |
| Bounded CUIntMax | |
| Bounded CUIntPtr | |
| Bounded CULLong | |
| Bounded CULong | |
| Bounded CUShort | |
| Bounded CWchar | |
| Bounded ByteOrder | Since: base-4.11.0.0 |
| Bounded Associativity | Since: base-4.9.0.0 |
Defined in GHC.Generics | |
| Bounded DecidedStrictness | Since: base-4.9.0.0 |
Defined in GHC.Generics | |
| Bounded SourceStrictness | Since: base-4.9.0.0 |
Defined in GHC.Generics | |
| Bounded SourceUnpackedness | Since: base-4.9.0.0 |
Defined in GHC.Generics | |
| Bounded Int16 | Since: base-2.1 |
| Bounded Int32 | Since: base-2.1 |
| Bounded Int64 | Since: base-2.1 |
| Bounded Int8 | Since: base-2.1 |
| Bounded Word16 | Since: base-2.1 |
| Bounded Word32 | Since: base-2.1 |
| Bounded Word64 | Since: base-2.1 |
| Bounded Word8 | Since: base-2.1 |
| Bounded Encoding | |
| Bounded UTF32_Invalid | |
Defined in Basement.String.Encoding.UTF32 | |
| Bounded Extension | |
| Bounded Ordering | Since: base-2.1 |
| Bounded StdMethod | |
| Bounded Status | Since: http-types-0.11 |
| Bounded IPv4 | |
| Bounded IPv6 | |
| Bounded VarType | |
| Bounded SessionFreeze Source # | |
Defined in Session.Freeze | |
| Bounded KeyRotation Source # | |
Defined in Session.KeyRotation | |
| Bounded CompressionStrategy | |
Defined in Codec.Compression.Zlib.Stream | |
| Bounded Format | |
| Bounded Method | |
| Bounded () | Since: base-2.1 |
| Bounded Bool | Since: base-2.1 |
| Bounded Char | Since: base-2.1 |
| Bounded Int | Since: base-2.1 |
| Bounded Levity | Since: base-4.16.0.0 |
| Bounded VecCount | Since: base-4.10.0.0 |
| Bounded VecElem | Since: base-4.10.0.0 |
| Bounded Word | Since: base-2.1 |
| Bounded a => Bounded (Identity a) | Since: base-4.9.0.0 |
| Bounded a => Bounded (Down a) | Swaps Since: base-4.14.0.0 |
| Bounded a => Bounded (First a) | Since: base-4.9.0.0 |
| Bounded a => Bounded (Last a) | Since: base-4.9.0.0 |
| Bounded a => Bounded (Max a) | Since: base-4.9.0.0 |
| Bounded a => Bounded (Min a) | Since: base-4.9.0.0 |
| Bounded m => Bounded (WrappedMonoid m) | Since: base-4.9.0.0 |
Defined in Data.Semigroup | |
| Bounded a => Bounded (Dual a) | Since: base-2.1 |
| Bounded a => Bounded (Product a) | Since: base-2.1 |
| Bounded a => Bounded (Sum a) | Since: base-2.1 |
| SizeValid n => Bounded (Bits n) | |
| Bounded a => Bounded (a) | |
| (Bounded a, Bounded b) => Bounded (Pair a b) | |
| (Bounded a, Bounded b) => Bounded (a, b) | Since: base-2.1 |
| Bounded a => Bounded (Const a b) | Since: base-4.9.0.0 |
| (Applicative f, Bounded a) => Bounded (Ap f a) | Since: base-4.12.0.0 |
| a ~ b => Bounded (a :~: b) | Since: base-4.7.0.0 |
| Bounded b => Bounded (Tagged s b) | |
| (Bounded a, Bounded b, Bounded c) => Bounded (a, b, c) | Since: base-2.1 |
| a ~~ b => Bounded (a :~~: b) | Since: base-4.10.0.0 |
| (Bounded a, Bounded b, Bounded c, Bounded d) => Bounded (a, b, c, d) | Since: base-2.1 |
| (Bounded a, Bounded b, Bounded c, Bounded d, Bounded e) => Bounded (a, b, c, d, e) | Since: base-2.1 |
| (Bounded a, Bounded b, Bounded c, Bounded d, Bounded e, Bounded f) => Bounded (a, b, c, d, e, f) | Since: base-2.1 |
| (Bounded a, Bounded b, Bounded c, Bounded d, Bounded e, Bounded f, Bounded g) => Bounded (a, b, c, d, e, f, g) | Since: base-2.1 |
| (Bounded a, Bounded b, Bounded c, Bounded d, Bounded e, Bounded f, Bounded g, Bounded h) => Bounded (a, b, c, d, e, f, g, h) | Since: base-2.1 |
| (Bounded a, Bounded b, Bounded c, Bounded d, Bounded e, Bounded f, Bounded g, Bounded h, Bounded i) => Bounded (a, b, c, d, e, f, g, h, i) | Since: base-2.1 |
| (Bounded a, Bounded b, Bounded c, Bounded d, Bounded e, Bounded f, Bounded g, Bounded h, Bounded i, Bounded j) => Bounded (a, b, c, d, e, f, g, h, i, j) | Since: base-2.1 |
| (Bounded a, Bounded b, Bounded c, Bounded d, Bounded e, Bounded f, Bounded g, Bounded h, Bounded i, Bounded j, Bounded k) => Bounded (a, b, c, d, e, f, g, h, i, j, k) | Since: base-2.1 |
| (Bounded a, Bounded b, Bounded c, Bounded d, Bounded e, Bounded f, Bounded g, Bounded h, Bounded i, Bounded j, Bounded k, Bounded l) => Bounded (a, b, c, d, e, f, g, h, i, j, k, l) | Since: base-2.1 |
| (Bounded a, Bounded b, Bounded c, Bounded d, Bounded e, Bounded f, Bounded g, Bounded h, Bounded i, Bounded j, Bounded k, Bounded l, Bounded m) => Bounded (a, b, c, d, e, f, g, h, i, j, k, l, m) | Since: base-2.1 |
| (Bounded a, Bounded b, Bounded c, Bounded d, Bounded e, Bounded f, Bounded g, Bounded h, Bounded i, Bounded j, Bounded k, Bounded l, Bounded m, Bounded n) => Bounded (a, b, c, d, e, f, g, h, i, j, k, l, m, n) | Since: base-2.1 |
| (Bounded a, Bounded b, Bounded c, Bounded d, Bounded e, Bounded f, Bounded g, Bounded h, Bounded i, Bounded j, Bounded k, Bounded l, Bounded m, Bounded n, Bounded o) => Bounded (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) | Since: base-2.1 |
Class Enum defines operations on sequentially ordered types.
The enumFrom... methods are used in Haskell's translation of
arithmetic sequences.
Instances of Enum may be derived for any enumeration type (types
whose constructors have no fields). The nullary constructors are
assumed to be numbered left-to-right by fromEnum from 0 through n-1.
See Chapter 10 of the Haskell Report for more details.
For any type that is an instance of class Bounded as well as Enum,
the following should hold:
- The calls
succmaxBoundpredminBound fromEnumandtoEnumshould give a runtime error if the result value is not representable in the result type. For example,toEnum7 ::BoolenumFromandenumFromThenshould be defined with an implicit bound, thus:
enumFrom x = enumFromTo x maxBound
enumFromThen x y = enumFromThenTo x y bound
where
bound | fromEnum y >= fromEnum x = maxBound
| otherwise = minBoundMethods
the successor of a value. For numeric types, succ adds 1.
the predecessor of a value. For numeric types, pred subtracts 1.
Instances
class (Real a, Fractional a) => RealFrac a where #
Extracting components of fractions.
Minimal complete definition
Methods
truncate :: Integral b => a -> b #
truncate xx between zero and x
ceiling :: Integral b => a -> b #
ceiling xx
floor :: Integral b => a -> b #
floor xx
Instances
| RealFrac CDouble | |
| RealFrac CFloat | |
| RealFrac Scientific | WARNING: the methods of the |
Defined in Data.Scientific Methods properFraction :: Integral b => Scientific -> (b, Scientific) # truncate :: Integral b => Scientific -> b # round :: Integral b => Scientific -> b # ceiling :: Integral b => Scientific -> b # floor :: Integral b => Scientific -> b # | |
| RealFrac DiffTime | |
| RealFrac NominalDiffTime | |
Defined in Data.Time.Clock.Internal.NominalDiffTime Methods properFraction :: Integral b => NominalDiffTime -> (b, NominalDiffTime) # truncate :: Integral b => NominalDiffTime -> b # round :: Integral b => NominalDiffTime -> b # ceiling :: Integral b => NominalDiffTime -> b # floor :: Integral b => NominalDiffTime -> b # | |
| RealFrac a => RealFrac (Identity a) | Since: base-4.9.0.0 |
| RealFrac a => RealFrac (Down a) | Since: base-4.14.0.0 |
| Integral a => RealFrac (Ratio a) | Since: base-2.0.1 |
| HasResolution a => RealFrac (Fixed a) | Since: base-2.1 |
| RealFrac a => RealFrac (Const a b) | Since: base-4.9.0.0 |
| RealFrac a => RealFrac (Tagged s a) | |
class (Real a, Enum a) => Integral a where #
Integral numbers, supporting integer division.
The Haskell Report defines no laws for Integral. However, Integral
instances are customarily expected to define a Euclidean domain and have the
following properties for the div/mod and quot/rem pairs, given
suitable Euclidean functions f and g:
x=y * quot x y + rem x ywithrem x y=fromInteger 0org (rem x y)<g yx=y * div x y + mod x ywithmod x y=fromInteger 0orf (mod x y)<f y
An example of a suitable Euclidean function, for Integer's instance, is
abs.
In addition, toInteger should be total, and fromInteger should be a left
inverse for it, i.e. fromInteger (toInteger i) = i.
Instances
Parsing of Strings, producing values.
Derived instances of Read make the following assumptions, which
derived instances of Show obey:
- If the constructor is defined to be an infix operator, then the
derived
Readinstance will parse only infix applications of the constructor (not the prefix form). - Associativity is not used to reduce the occurrence of parentheses, although precedence may be.
- If the constructor is defined using record syntax, the derived
Readwill parse only the record-syntax form, and furthermore, the fields must be given in the same order as the original declaration. - The derived
Readinstance allows arbitrary Haskell whitespace between tokens of the input string. Extra parentheses are also allowed.
For example, given the declarations
infixr 5 :^: data Tree a = Leaf a | Tree a :^: Tree a
the derived instance of Read in Haskell 2010 is equivalent to
instance (Read a) => Read (Tree a) where
readsPrec d r = readParen (d > app_prec)
(\r -> [(Leaf m,t) |
("Leaf",s) <- lex r,
(m,t) <- readsPrec (app_prec+1) s]) r
++ readParen (d > up_prec)
(\r -> [(u:^:v,w) |
(u,s) <- readsPrec (up_prec+1) r,
(":^:",t) <- lex s,
(v,w) <- readsPrec (up_prec+1) t]) r
where app_prec = 10
up_prec = 5Note that right-associativity of :^: is unused.
The derived instance in GHC is equivalent to
instance (Read a) => Read (Tree a) where
readPrec = parens $ (prec app_prec $ do
Ident "Leaf" <- lexP
m <- step readPrec
return (Leaf m))
+++ (prec up_prec $ do
u <- step readPrec
Symbol ":^:" <- lexP
v <- step readPrec
return (u :^: v))
where app_prec = 10
up_prec = 5
readListPrec = readListPrecDefaultWhy do both readsPrec and readPrec exist, and why does GHC opt to
implement readPrec in derived Read instances instead of readsPrec?
The reason is that readsPrec is based on the ReadS type, and although
ReadS is mentioned in the Haskell 2010 Report, it is not a very efficient
parser data structure.
readPrec, on the other hand, is based on a much more efficient ReadPrec
datatype (a.k.a "new-style parsers"), but its definition relies on the use
of the RankNTypes language extension. Therefore, readPrec (and its
cousin, readListPrec) are marked as GHC-only. Nevertheless, it is
recommended to use readPrec instead of readsPrec whenever possible
for the efficiency improvements it brings.
As mentioned above, derived Read instances in GHC will implement
readPrec instead of readsPrec. The default implementations of
readsPrec (and its cousin, readList) will simply use readPrec under
the hood. If you are writing a Read instance by hand, it is recommended
to write it like so:
instanceReadT wherereadPrec= ...readListPrec=readListPrecDefault
Instances
| Read Key | |
| Read DotNetTime | |
Defined in Data.Aeson.Types.Internal Methods readsPrec :: Int -> ReadS DotNetTime # readList :: ReadS [DotNetTime] # readPrec :: ReadPrec DotNetTime # readListPrec :: ReadPrec [DotNetTime] # | |
| Read Value | |
| Read All | Since: base-2.1 |
| Read Any | Since: base-2.1 |
| Read Version | Since: base-2.1 |
| Read CBool | |
| Read CChar | |
| Read CClock | |
| Read CDouble | |
| Read CFloat | |
| Read CInt | |
| Read CIntMax | |
| Read CIntPtr | |
| Read CLLong | |
| Read CLong | |
| Read CPtrdiff | |
| Read CSChar | |
| Read CSUSeconds | |
Defined in Foreign.C.Types Methods readsPrec :: Int -> ReadS CSUSeconds # readList :: ReadS [CSUSeconds] # readPrec :: ReadPrec CSUSeconds # readListPrec :: ReadPrec [CSUSeconds] # | |
| Read CShort | |
| Read CSigAtomic | |
Defined in Foreign.C.Types Methods readsPrec :: Int -> ReadS CSigAtomic # readList :: ReadS [CSigAtomic] # readPrec :: ReadPrec CSigAtomic # readListPrec :: ReadPrec [CSigAtomic] # | |
| Read CSize | |
| Read CTime | |
| Read CUChar | |
| Read CUInt | |
| Read CUIntMax | |
| Read CUIntPtr | |
| Read CULLong | |
| Read CULong | |
| Read CUSeconds | |
| Read CUShort | |
| Read CWchar | |
| Read Void | Reading a Since: base-4.8.0.0 |
| Read ByteOrder | Since: base-4.11.0.0 |
| Read Associativity | Since: base-4.6.0.0 |
Defined in GHC.Generics Methods readsPrec :: Int -> ReadS Associativity # readList :: ReadS [Associativity] # | |
| Read DecidedStrictness | Since: base-4.9.0.0 |
Defined in GHC.Generics Methods readsPrec :: Int -> ReadS DecidedStrictness # readList :: ReadS [DecidedStrictness] # | |
| Read Fixity | Since: base-4.6.0.0 |
| Read SourceStrictness | Since: base-4.9.0.0 |
Defined in GHC.Generics Methods readsPrec :: Int -> ReadS SourceStrictness # readList :: ReadS [SourceStrictness] # | |
| Read SourceUnpackedness | Since: base-4.9.0.0 |
Defined in GHC.Generics Methods readsPrec :: Int -> ReadS SourceUnpackedness # readList :: ReadS [SourceUnpackedness] # | |
| Read ExitCode | |
| Read Int16 | Since: base-2.1 |
| Read Int32 | Since: base-2.1 |
| Read Int64 | Since: base-2.1 |
| Read Int8 | Since: base-2.1 |
| Read GCDetails | Since: base-4.10.0.0 |
| Read RTSStats | Since: base-4.10.0.0 |
| Read SomeNat | Since: base-4.7.0.0 |
| Read GeneralCategory | Since: base-2.1 |
Defined in GHC.Read Methods readsPrec :: Int -> ReadS GeneralCategory # readList :: ReadS [GeneralCategory] # | |
| Read Word16 | Since: base-2.1 |
| Read Word32 | Since: base-2.1 |
| Read Word64 | Since: base-2.1 |
| Read Word8 | Since: base-2.1 |
| Read Lexeme | Since: base-2.1 |
| Read ByteString | |
Defined in Data.ByteString.Internal.Type Methods readsPrec :: Int -> ReadS ByteString # readList :: ReadS [ByteString] # readPrec :: ReadPrec ByteString # readListPrec :: ReadPrec [ByteString] # | |
| Read ByteString | |
Defined in Data.ByteString.Lazy.Internal Methods readsPrec :: Int -> ReadS ByteString # readList :: ReadS [ByteString] # readPrec :: ReadPrec ByteString # readListPrec :: ReadPrec [ByteString] # | |
| Read ShortByteString | |
Defined in Data.ByteString.Short.Internal Methods readsPrec :: Int -> ReadS ShortByteString # readList :: ReadS [ShortByteString] # | |
| Read IntSet | |
| Read Ordering | Since: base-2.1 |
| Read StdMethod | |
| Read IP | |
| Read IPv4 | |
| Read IPv6 | |
| Read IPRange | |
| Read LogLevel | |
| Read AddrInfoFlag | |
Defined in Network.Socket.Info Methods readsPrec :: Int -> ReadS AddrInfoFlag # readList :: ReadS [AddrInfoFlag] # | |
| Read NameInfoFlag | |
Defined in Network.Socket.Info Methods readsPrec :: Int -> ReadS NameInfoFlag # readList :: ReadS [NameInfoFlag] # | |
| Read Scientific | Supports the skipping of parentheses and whitespaces. Example: > read " ( (( -1.0e+3 ) ))" :: Scientific -1000.0 (Note: This |
Defined in Data.Scientific Methods readsPrec :: Int -> ReadS Scientific # readList :: ReadS [Scientific] # readPrec :: ReadPrec Scientific # readListPrec :: ReadPrec [Scientific] # | |
| Read ShortText | |
| Read DatatypeVariant | |
Defined in Language.Haskell.TH.Datatype Methods readsPrec :: Int -> ReadS DatatypeVariant # readList :: ReadS [DatatypeVariant] # | |
| Read DiffTime | |
| Read NominalDiffTime | |
Defined in Data.Time.Clock.Internal.NominalDiffTime Methods readsPrec :: Int -> ReadS NominalDiffTime # readList :: ReadS [NominalDiffTime] # | |
| Read UUID | |
| Read UnpackedUUID | |
| Read AuthResult | |
Defined in Yesod.Core.Types Methods readsPrec :: Int -> ReadS AuthResult # readList :: ReadS [AuthResult] # readPrec :: ReadPrec AuthResult # readListPrec :: ReadPrec [AuthResult] # | |
| Read SessionCookie | |
Defined in Yesod.Core.Types Methods readsPrec :: Int -> ReadS SessionCookie # readList :: ReadS [SessionCookie] # | |
| Read SessionFreeze Source # | |
Defined in Session.Freeze Methods readsPrec :: Int -> ReadS SessionFreeze # readList :: ReadS [SessionFreeze] # | |
| Read KeyRotation Source # | |
Defined in Session.KeyRotation Methods readsPrec :: Int -> ReadS KeyRotation # readList :: ReadS [KeyRotation] # readPrec :: ReadPrec KeyRotation # readListPrec :: ReadPrec [KeyRotation] # | |
| Read DictionaryHash | |
| Read Integer | Since: base-2.1 |
| Read Natural | Since: base-4.8.0.0 |
| Read () | Since: base-2.1 |
| Read Bool | Since: base-2.1 |
| Read Char | Since: base-2.1 |
| Read Double | Since: base-2.1 |
| Read Float | Since: base-2.1 |
| Read Int | Since: base-2.1 |
| Read Word | Since: base-4.5.0.0 |
| Read v => Read (KeyMap v) | |
| Read a => Read (ZipList a) | Since: base-4.7.0.0 |
| Read a => Read (Complex a) | Since: base-2.1 |
| Read a => Read (Identity a) | This instance would be equivalent to the derived instances of the
Since: base-4.8.0.0 |
| Read a => Read (First a) | Since: base-2.1 |
| Read a => Read (Last a) | Since: base-2.1 |
| Read a => Read (Down a) | This instance would be equivalent to the derived instances of the
Since: base-4.7.0.0 |
| Read a => Read (First a) | Since: base-4.9.0.0 |
| Read a => Read (Last a) | Since: base-4.9.0.0 |
| Read a => Read (Max a) | Since: base-4.9.0.0 |
| Read a => Read (Min a) | Since: base-4.9.0.0 |
| Read m => Read (WrappedMonoid m) | Since: base-4.9.0.0 |
Defined in Data.Semigroup Methods readsPrec :: Int -> ReadS (WrappedMonoid m) # readList :: ReadS [WrappedMonoid m] # readPrec :: ReadPrec (WrappedMonoid m) # readListPrec :: ReadPrec [WrappedMonoid m] # | |
| Read a => Read (Dual a) | Since: base-2.1 |
| Read a => Read (Product a) | Since: base-2.1 |
| Read a => Read (Sum a) | Since: base-2.1 |
| Read a => Read (NonEmpty a) | Since: base-4.11.0.0 |
| Read p => Read (Par1 p) | Since: base-4.7.0.0 |
| (Integral a, Read a) => Read (Ratio a) | Since: base-2.1 |
| (Read s, FoldCase s) => Read (CI s) | |
| Read e => Read (IntMap e) | |
| Read a => Read (Seq a) | |
| Read a => Read (ViewL a) | |
| Read a => Read (ViewR a) | |
| (Read a, Ord a) => Read (Set a) | |
| Read a => Read (Tree a) | |
| HashAlgorithm a => Read (Digest a) | |
| Read1 f => Read (Fix f) | |
| (Functor f, Read1 f) => Read (Mu f) | |
| (Functor f, Read1 f) => Read (Nu f) | |
| Read a => Read (DNonEmpty a) | |
| Read a => Read (DList a) | |
| Read (AddrRange IPv4) | |
| Read (AddrRange IPv6) | |
| Read mono => Read (NonNull mono) | |
| (Read (Key record), Read record) => Read (Entity record) | |
| Read a => Read (Single a) | |
| Read a => Read (Array a) | |
| Read a => Read (SmallArray a) | |
Defined in Data.Primitive.SmallArray Methods readsPrec :: Int -> ReadS (SmallArray a) # readList :: ReadS [SmallArray a] # readPrec :: ReadPrec (SmallArray a) # readListPrec :: ReadPrec [SmallArray a] # | |
| Read a => Read (Maybe a) | |
| (Eq a, Hashable a, Read a) => Read (HashSet a) | |
| Read a => Read (Vector a) | |
| (Read a, Prim a) => Read (Vector a) | |
| (Read a, Storable a) => Read (Vector a) | |
| Read (Route LiteApp) | |
| Read (Route WaiSubsite) | |
Defined in Yesod.Core.Types Methods readsPrec :: Int -> ReadS (Route WaiSubsite) # readList :: ReadS [Route WaiSubsite] # readPrec :: ReadPrec (Route WaiSubsite) # readListPrec :: ReadPrec [Route WaiSubsite] # | |
| Read (Route WaiSubsiteWithAuth) | |
Defined in Yesod.Core.Types | |
| Read a => Read (Maybe a) | Since: base-2.1 |
| Read a => Read (a) | Since: base-4.15 |
| Read a => Read [a] | Since: base-2.1 |
| (Read a, Read b) => Read (Either a b) | Since: base-3.0 |
| HasResolution a => Read (Fixed a) | Since: base-4.3.0.0 |
| (Read a, Read b) => Read (Arg a b) | Since: base-4.9.0.0 |
| (Ix a, Read a, Read b) => Read (Array a b) | Since: base-2.1 |
| Read (U1 p) | Since: base-4.9.0.0 |
| Read (V1 p) | Since: base-4.9.0.0 |
| (Ord k, Read k, Read e) => Read (Map k e) | |
| (Read a, Read b) => Read (Either a b) | |
| (Read a, Read b) => Read (These a b) | |
| (Read a, Read b) => Read (Pair a b) | |
| (Read a, Read b) => Read (These a b) | |
| (Read1 m, Read a) => Read (MaybeT m a) | |
| (Eq k, Hashable k, Read k, Read e) => Read (HashMap k e) | |
| (Read a, Read b) => Read (a, b) | Since: base-2.1 |
| Read a => Read (Const a b) | This instance would be equivalent to the derived instances of the
Since: base-4.8.0.0 |
| Read (f a) => Read (Ap f a) | Since: base-4.12.0.0 |
| Read (f a) => Read (Alt f a) | Since: base-4.8.0.0 |
| a ~ b => Read (a :~: b) | Since: base-4.7.0.0 |
| Read (f p) => Read (Rec1 f p) | Since: base-4.7.0.0 |
| Read b => Read (Tagged s b) | |
| (Read (f a), Read (g a), Read a) => Read (These1 f g a) | |
| (Read1 f, Read a) => Read (Backwards f a) | |
| (Read e, Read1 m, Read a) => Read (ExceptT e m a) | |
| (Read1 f, Read a) => Read (IdentityT f a) | |
| (Read w, Read1 m, Read a) => Read (WriterT w m a) | |
| (Read w, Read1 m, Read a) => Read (WriterT w m a) | |
| Read a => Read (Constant a b) | |
| (Read1 f, Read a) => Read (Reverse f a) | |
| (Read a, Read b, Read c) => Read (a, b, c) | Since: base-2.1 |
| (Read (f a), Read (g a)) => Read (Product f g a) | Since: base-4.18.0.0 |
| (Read (f a), Read (g a)) => Read (Sum f g a) | Since: base-4.18.0.0 |
| a ~~ b => Read (a :~~: b) | Since: base-4.10.0.0 |
| (Read (f p), Read (g p)) => Read ((f :*: g) p) | Since: base-4.7.0.0 |
| (Read (f p), Read (g p)) => Read ((f :+: g) p) | Since: base-4.7.0.0 |
| Read c => Read (K1 i c p) | Since: base-4.7.0.0 |
| (Read a, Read b, Read c, Read d) => Read (a, b, c, d) | Since: base-2.1 |
| Read (f (g a)) => Read (Compose f g a) | Since: base-4.18.0.0 |
| Read (f (g p)) => Read ((f :.: g) p) | Since: base-4.7.0.0 |
| Read (f p) => Read (M1 i c f p) | Since: base-4.7.0.0 |
| (Read a, Read b, Read c, Read d, Read e) => Read (a, b, c, d, e) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f) => Read (a, b, c, d, e, f) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f, Read g) => Read (a, b, c, d, e, f, g) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f, Read g, Read h) => Read (a, b, c, d, e, f, g, h) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f, Read g, Read h, Read i) => Read (a, b, c, d, e, f, g, h, i) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f, Read g, Read h, Read i, Read j) => Read (a, b, c, d, e, f, g, h, i, j) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f, Read g, Read h, Read i, Read j, Read k) => Read (a, b, c, d, e, f, g, h, i, j, k) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f, Read g, Read h, Read i, Read j, Read k, Read l) => Read (a, b, c, d, e, f, g, h, i, j, k, l) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f, Read g, Read h, Read i, Read j, Read k, Read l, Read m) => Read (a, b, c, d, e, f, g, h, i, j, k, l, m) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f, Read g, Read h, Read i, Read j, Read k, Read l, Read m, Read n) => Read (a, b, c, d, e, f, g, h, i, j, k, l, m, n) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f, Read g, Read h, Read i, Read j, Read k, Read l, Read m, Read n, Read o) => Read (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) | Since: base-2.1 |
Defined in GHC.Read | |
type family (a :: k) == (b :: k) :: Bool where ... infix 4 #
A type family to compute Boolean equality.
The Ord class is used for totally ordered datatypes.
Instances of Ord can be derived for any user-defined datatype whose
constituent types are in Ord. The declared order of the constructors in
the data declaration determines the ordering in derived Ord instances. The
Ordering datatype allows a single comparison to determine the precise
ordering of two objects.
Ord, as defined by the Haskell report, implements a total order and has the
following properties:
- Comparability
x <= y || y <= x=True- Transitivity
- if
x <= y && y <= z=True, thenx <= z=True - Reflexivity
x <= x=True- Antisymmetry
- if
x <= y && y <= x=True, thenx == y=True
The following operator interactions are expected to hold:
x >= y=y <= xx < y=x <= y && x /= yx > y=y < xx < y=compare x y == LTx > y=compare x y == GTx == y=compare x y == EQmin x y == if x <= y then x else y=Truemax x y == if x >= y then x else y=True
Note that (7.) and (8.) do not require min and max to return either of
their arguments. The result is merely required to equal one of the
arguments in terms of (==).
Minimal complete definition: either compare or <=.
Using compare can be more efficient for complex types.
Methods
compare :: a -> a -> Ordering #
(<) :: a -> a -> Bool infix 4 #
(<=) :: a -> a -> Bool infix 4 #
(>) :: a -> a -> Bool infix 4 #
Instances
The Eq class defines equality (==) and inequality (/=).
All the basic datatypes exported by the Prelude are instances of Eq,
and Eq may be derived for any datatype whose constituents are also
instances of Eq.
The Haskell Report defines no laws for Eq. However, instances are
encouraged to follow these properties:
Instances
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
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
| Bifoldable Map | Since: containers-0.6.3.1 |
| Eq2 Map | Since: containers-0.5.9 |
| Ord2 Map | Since: containers-0.5.9 |
Defined in Data.Map.Internal | |
| Show2 Map | Since: containers-0.5.9 |
| Hashable2 Map | Since: hashable-1.3.4.0 |
Defined in Data.Hashable.Class | |
| (Monad m, Ord k) => MapOperations k v (StateT (Map k v) m) Source # | |
| (Lift k, Lift a) => Lift (Map k a :: Type) | Since: containers-0.6.6 |
| (key ~ Text, val ~ Text) => RedirectUrl master (Route master, Map key val) | |
Defined in Yesod.Core.Handler Methods toTextUrl :: (MonadHandler m, HandlerSite m ~ master) => (Route master, Map key val) -> m Text # | |
| (Ord k, Arbitrary k) => Arbitrary1 (Map k) | |
Defined in Test.QuickCheck.Arbitrary | |
| (FromJSONKey k, Ord k) => FromJSON1 (Map k) | |
Defined in Data.Aeson.Types.FromJSON | |
| ToJSONKey k => ToJSON1 (Map k) | |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON :: (a -> Bool) -> (a -> Value) -> ([a] -> Value) -> Map k a -> Value # liftToJSONList :: (a -> Bool) -> (a -> Value) -> ([a] -> Value) -> [Map k a] -> Value # liftToEncoding :: (a -> Bool) -> (a -> Encoding) -> ([a] -> Encoding) -> Map k a -> Encoding # liftToEncodingList :: (a -> Bool) -> (a -> Encoding) -> ([a] -> Encoding) -> [Map k a] -> Encoding # liftOmitField :: (a -> Bool) -> Map k a -> Bool # | |
| Foldable (Map k) | Folds in order of increasing key. |
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 # elem :: Eq a => a -> Map k a -> Bool # maximum :: Ord a => Map k a -> a # minimum :: Ord a => Map k a -> a # | |
| Eq k => Eq1 (Map k) | Since: containers-0.5.9 |
| Ord k => Ord1 (Map k) | Since: containers-0.5.9 |
Defined in Data.Map.Internal | |
| (Ord k, Read k) => Read1 (Map k) | Since: containers-0.5.9 |
Defined in Data.Map.Internal | |
| Show k => Show1 (Map k) | Since: containers-0.5.9 |
| Traversable (Map k) | Traverses in order of increasing key. |
| Functor (Map k) | |
| Hashable k => Hashable1 (Map k) | Since: hashable-1.3.4.0 |
Defined in Data.Hashable.Class | |
| (Ord k, Arbitrary k, Arbitrary v) => Arbitrary (Map k v) | |
| (CoArbitrary k, CoArbitrary v) => CoArbitrary (Map k v) | |
Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Map k v -> Gen b -> Gen b # | |
| (FromJSONKey k, Ord k, FromJSON v) => FromJSON (Map k v) | |
Defined in Data.Aeson.Types.FromJSON | |
| (ToJSON v, ToJSONKey k) => ToJSON (Map k v) | |
| (Data k, Data a, Ord k) => Data (Map k a) | |
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) | |
| Ord k => Semigroup (Map k v) | |
| Ord k => IsList (Map k v) | Since: containers-0.5.6.2 |
| (Ord k, Read k, Read e) => Read (Map k e) | |
| (Show k, Show a) => Show (Map k a) | |
| (NFData k, NFData a) => NFData (Map k a) | |
Defined in Data.Map.Internal | |
| (Eq k, Eq a) => Eq (Map k a) | |
| (Ord k, Ord v) => Ord (Map k v) | |
| (Hashable k, Hashable v) => Hashable (Map k v) | Since: hashable-1.3.4.0 |
Defined in Data.Hashable.Class | |
| Ord k => GrowingAppend (Map k v) | |
Defined in Data.MonoTraversable | |
| MonoFoldable (Map k v) | |
Defined in Data.MonoTraversable Methods ofoldMap :: Monoid m => (Element (Map k v) -> m) -> Map k v -> m # ofoldr :: (Element (Map k v) -> b -> b) -> b -> Map k v -> b # ofoldl' :: (a -> Element (Map k v) -> a) -> a -> Map k v -> a # otoList :: Map k v -> [Element (Map k v)] # oall :: (Element (Map k v) -> Bool) -> Map k v -> Bool # oany :: (Element (Map k v) -> Bool) -> Map k v -> Bool # olength64 :: Map k v -> Int64 # ocompareLength :: Integral i => Map k v -> i -> Ordering # otraverse_ :: Applicative f => (Element (Map k v) -> f b) -> Map k v -> f () # ofor_ :: Applicative f => Map k v -> (Element (Map k v) -> f b) -> f () # omapM_ :: Applicative m => (Element (Map k v) -> m ()) -> Map k v -> m () # oforM_ :: Applicative m => Map k v -> (Element (Map k v) -> m ()) -> m () # ofoldlM :: Monad m => (a -> Element (Map k v) -> m a) -> a -> Map k v -> m a # ofoldMap1Ex :: Semigroup m => (Element (Map k v) -> m) -> Map k v -> m # ofoldr1Ex :: (Element (Map k v) -> Element (Map k v) -> Element (Map k v)) -> Map k v -> Element (Map k v) # ofoldl1Ex' :: (Element (Map k v) -> Element (Map k v) -> Element (Map k v)) -> Map k v -> Element (Map k v) # headEx :: Map k v -> Element (Map k v) # lastEx :: Map k v -> Element (Map k v) # unsafeHead :: Map k v -> Element (Map k v) # unsafeLast :: Map k v -> Element (Map k v) # maximumByEx :: (Element (Map k v) -> Element (Map k v) -> Ordering) -> Map k v -> Element (Map k v) # minimumByEx :: (Element (Map k v) -> Element (Map k v) -> Ordering) -> Map k v -> Element (Map k v) # | |
| MonoFunctor (Map k v) | |
| MonoTraversable (Map k v) | |
| PersistField v => PersistField (Map Text v) | |
Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Map Text v -> PersistValue # fromPersistValue :: PersistValue -> Either Text (Map Text v) # | |
| type Item (Map k v) | |
Defined in Data.Map.Internal | |
| type Element (Map k v) | |
Defined in Data.MonoTraversable | |
32-bit unsigned integer type
Instances
A space efficient, packed, unboxed Unicode text type.
Instances
The Either type represents values with two possibilities: a value of
type Either a bLeft aRight b
The Either type is sometimes used to represent a value which is
either correct or an error; by convention, the Left constructor is
used to hold an error value and the Right constructor is used to
hold a correct value (mnemonic: "right" also means "correct").
Examples
The type Either String IntString or an Int. The Left constructor can be used only on
Strings, and the Right constructor can be used only on Ints:
>>>let s = Left "foo" :: Either String Int>>>sLeft "foo">>>let n = Right 3 :: Either String Int>>>nRight 3>>>:type ss :: Either String Int>>>:type nn :: Either String Int
The fmap from our Functor instance will ignore Left values, but
will apply the supplied function to values contained in a Right:
>>>let s = Left "foo" :: Either String Int>>>let n = Right 3 :: Either String Int>>>fmap (*2) sLeft "foo">>>fmap (*2) nRight 6
The Monad instance for Either allows us to chain together multiple
actions which may fail, and fail overall if any of the individual
steps failed. First we'll write a function that can either parse an
Int from a Char, or fail.
>>>import Data.Char ( digitToInt, isDigit )>>>:{let parseEither :: Char -> Either String Int parseEither c | isDigit c = Right (digitToInt c) | otherwise = Left "parse error">>>:}
The following should work, since both '1' and '2' can be
parsed as Ints.
>>>:{let parseMultiple :: Either String Int parseMultiple = do x <- parseEither '1' y <- parseEither '2' return (x + y)>>>:}
>>>parseMultipleRight 3
But the following should fail overall, since the first operation where
we attempt to parse 'm' as an Int will fail:
>>>:{let parseMultiple :: Either String Int parseMultiple = do x <- parseEither 'm' y <- parseEither '2' return (x + y)>>>:}
>>>parseMultipleLeft "parse error"
Instances
| Arbitrary2 Either | |
Defined in Test.QuickCheck.Arbitrary Methods liftArbitrary2 :: Gen a -> Gen b -> Gen (Either a b) # liftShrink2 :: (a -> [a]) -> (b -> [b]) -> Either a b -> [Either a b] # | |
| FromJSON2 Either | |
Defined in Data.Aeson.Types.FromJSON Methods liftParseJSON2 :: Maybe a -> (Value -> Parser a) -> (Value -> Parser [a]) -> Maybe b -> (Value -> Parser b) -> (Value -> Parser [b]) -> Value -> Parser (Either a b) # liftParseJSONList2 :: Maybe a -> (Value -> Parser a) -> (Value -> Parser [a]) -> Maybe b -> (Value -> Parser b) -> (Value -> Parser [b]) -> Value -> Parser [Either a b] # liftOmittedField2 :: Maybe a -> Maybe b -> Maybe (Either a b) # | |
| ToJSON2 Either | |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON2 :: (a -> Bool) -> (a -> Value) -> ([a] -> Value) -> (b -> Bool) -> (b -> Value) -> ([b] -> Value) -> Either a b -> Value # liftToJSONList2 :: (a -> Bool) -> (a -> Value) -> ([a] -> Value) -> (b -> Bool) -> (b -> Value) -> ([b] -> Value) -> [Either a b] -> Value # liftToEncoding2 :: (a -> Bool) -> (a -> Encoding) -> ([a] -> Encoding) -> (b -> Bool) -> (b -> Encoding) -> ([b] -> Encoding) -> Either a b -> Encoding # liftToEncodingList2 :: (a -> Bool) -> (a -> Encoding) -> ([a] -> Encoding) -> (b -> Bool) -> (b -> Encoding) -> ([b] -> Encoding) -> [Either a b] -> Encoding # liftOmitField2 :: (a -> Bool) -> (b -> Bool) -> Either a b -> Bool # | |
| Bifunctor Either | Since: base-4.8.0.0 |
| NFData2 Either | Since: deepseq-1.4.3.0 |
Defined in Control.DeepSeq | |
| Hashable2 Either | |
Defined in Data.Hashable.Class | |
| Generic1 (Either a :: Type -> Type) | |
| MonadError e (Either e) | |
Defined in Control.Monad.Error.Class | |
| (Lift a, Lift b) => Lift (Either a b :: Type) | |
| Arbitrary a => Arbitrary1 (Either a) | |
Defined in Test.QuickCheck.Arbitrary Methods liftArbitrary :: Gen a0 -> Gen (Either a a0) # liftShrink :: (a0 -> [a0]) -> Either a a0 -> [Either a a0] # | |
| FromJSON a => FromJSON1 (Either a) | |
Defined in Data.Aeson.Types.FromJSON | |
| ToJSON a => ToJSON1 (Either a) | |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON :: (a0 -> Bool) -> (a0 -> Value) -> ([a0] -> Value) -> Either a a0 -> Value # liftToJSONList :: (a0 -> Bool) -> (a0 -> Value) -> ([a0] -> Value) -> [Either a a0] -> Value # liftToEncoding :: (a0 -> Bool) -> (a0 -> Encoding) -> ([a0] -> Encoding) -> Either a a0 -> Encoding # liftToEncodingList :: (a0 -> Bool) -> (a0 -> Encoding) -> ([a0] -> Encoding) -> [Either a a0] -> Encoding # liftOmitField :: (a0 -> Bool) -> Either a a0 -> Bool # | |
| Foldable (Either a) | Since: base-4.7.0.0 |
Defined in Data.Foldable Methods fold :: Monoid m => Either a m -> m # foldMap :: Monoid m => (a0 -> m) -> Either a a0 -> m # foldMap' :: Monoid m => (a0 -> m) -> Either a a0 -> m # foldr :: (a0 -> b -> b) -> b -> Either a a0 -> b # foldr' :: (a0 -> b -> b) -> b -> Either a a0 -> b # foldl :: (b -> a0 -> b) -> b -> Either a a0 -> b # foldl' :: (b -> a0 -> b) -> b -> Either a a0 -> b # foldr1 :: (a0 -> a0 -> a0) -> Either a a0 -> a0 # foldl1 :: (a0 -> a0 -> a0) -> Either a a0 -> a0 # toList :: Either a a0 -> [a0] # length :: Either a a0 -> Int # elem :: Eq a0 => a0 -> Either a a0 -> Bool # maximum :: Ord a0 => Either a a0 -> a0 # minimum :: Ord a0 => Either a a0 -> a0 # | |
| Traversable (Either a) | Since: base-4.7.0.0 |
Defined in Data.Traversable | |
| Applicative (Either e) | Since: base-3.0 |
| Functor (Either a) | Since: base-3.0 |
| Monad (Either e) | Since: base-4.4.0.0 |
| MonadFailure (Either a) | |
| NFData a => NFData1 (Either a) | Since: deepseq-1.4.3.0 |
Defined in Control.DeepSeq | |
| e ~ SomeException => MonadCatch (Either e) | Since: exceptions-0.8.3 |
Defined in Control.Monad.Catch | |
| e ~ SomeException => MonadMask (Either e) | Since: exceptions-0.8.3 |
Defined in Control.Monad.Catch Methods mask :: HasCallStack => ((forall a. Either e a -> Either e a) -> Either e b) -> Either e b # uninterruptibleMask :: HasCallStack => ((forall a. Either e a -> Either e a) -> Either e b) -> Either e b # generalBracket :: HasCallStack => Either e a -> (a -> ExitCase b -> Either e c) -> (a -> Either e b) -> Either e (b, c) # | |
| e ~ SomeException => MonadThrow (Either e) | |
Defined in Control.Monad.Catch Methods throwM :: (HasCallStack, Exception e0) => e0 -> Either e a # | |
| Hashable a => Hashable1 (Either a) | |
Defined in Data.Hashable.Class | |
| MonadBaseControl (Either e) (Either e) | |
| (Arbitrary a, Arbitrary b) => Arbitrary (Either a b) | |
| (CoArbitrary a, CoArbitrary b) => CoArbitrary (Either a b) | |
Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Either a b -> Gen b0 -> Gen b0 # | |
| (FromJSON a, FromJSON b) => FromJSON (Either a b) | |
Defined in Data.Aeson.Types.FromJSON | |
| (ToJSON a, ToJSON b) => ToJSON (Either a b) | |
| (Data a, Data b) => Data (Either a b) | Since: base-4.0.0.0 |
Defined in Data.Data Methods gfoldl :: (forall d b0. Data d => c (d -> b0) -> d -> c b0) -> (forall g. g -> c g) -> Either a b -> c (Either a b) # gunfold :: (forall b0 r. Data b0 => c (b0 -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Either a b) # toConstr :: Either a b -> Constr # dataTypeOf :: Either a b -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Either a b)) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Either a b)) # gmapT :: (forall b0. Data b0 => b0 -> b0) -> Either a b -> Either a b # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Either a b -> r # gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Either a b -> r # gmapQ :: (forall d. Data d => d -> u) -> Either a b -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> Either a b -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> Either a b -> m (Either a b) # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Either a b -> m (Either a b) # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Either a b -> m (Either a b) # | |
| Semigroup (Either a b) | Since: base-4.9.0.0 |
| Generic (Either a b) | |
| (Read a, Read b) => Read (Either a b) | Since: base-3.0 |
| (Show a, Show b) => Show (Either a b) | Since: base-3.0 |
| (NFData a, NFData b) => NFData (Either a b) | |
Defined in Control.DeepSeq | |
| (Eq a, Eq b) => Eq (Either a b) | Since: base-2.1 |
| (Ord a, Ord b) => Ord (Either a b) | Since: base-2.1 |
| (Hashable a, Hashable b) => Hashable (Either a b) | |
Defined in Data.Hashable.Class | |
| MonoFoldable (Either a b) | |
Defined in Data.MonoTraversable Methods ofoldMap :: Monoid m => (Element (Either a b) -> m) -> Either a b -> m # ofoldr :: (Element (Either a b) -> b0 -> b0) -> b0 -> Either a b -> b0 # ofoldl' :: (a0 -> Element (Either a b) -> a0) -> a0 -> Either a b -> a0 # otoList :: Either a b -> [Element (Either a b)] # oall :: (Element (Either a b) -> Bool) -> Either a b -> Bool # oany :: (Element (Either a b) -> Bool) -> Either a b -> Bool # olength :: Either a b -> Int # olength64 :: Either a b -> Int64 # ocompareLength :: Integral i => Either a b -> i -> Ordering # otraverse_ :: Applicative f => (Element (Either a b) -> f b0) -> Either a b -> f () # ofor_ :: Applicative f => Either a b -> (Element (Either a b) -> f b0) -> f () # omapM_ :: Applicative m => (Element (Either a b) -> m ()) -> Either a b -> m () # oforM_ :: Applicative m => Either a b -> (Element (Either a b) -> m ()) -> m () # ofoldlM :: Monad m => (a0 -> Element (Either a b) -> m a0) -> a0 -> Either a b -> m a0 # ofoldMap1Ex :: Semigroup m => (Element (Either a b) -> m) -> Either a b -> m # ofoldr1Ex :: (Element (Either a b) -> Element (Either a b) -> Element (Either a b)) -> Either a b -> Element (Either a b) # ofoldl1Ex' :: (Element (Either a b) -> Element (Either a b) -> Element (Either a b)) -> Either a b -> Element (Either a b) # headEx :: Either a b -> Element (Either a b) # lastEx :: Either a b -> Element (Either a b) # unsafeHead :: Either a b -> Element (Either a b) # unsafeLast :: Either a b -> Element (Either a b) # maximumByEx :: (Element (Either a b) -> Element (Either a b) -> Ordering) -> Either a b -> Element (Either a b) # minimumByEx :: (Element (Either a b) -> Element (Either a b) -> Ordering) -> Either a b -> Element (Either a b) # | |
| MonoFunctor (Either a b) | |
| MonoPointed (Either a b) | |
| MonoTraversable (Either a b) | |
| (PersistConfig c1, PersistConfig c2, PersistConfigPool c1 ~ PersistConfigPool c2, PersistConfigBackend c1 ~ PersistConfigBackend c2) => PersistConfig (Either c1 c2) | |
Defined in Database.Persist.Class.PersistConfig Associated Types type PersistConfigBackend (Either c1 c2) :: (Type -> Type) -> Type -> Type # type PersistConfigPool (Either c1 c2) # Methods loadConfig :: Value -> Parser (Either c1 c2) # applyEnv :: Either c1 c2 -> IO (Either c1 c2) # createPoolConfig :: Either c1 c2 -> IO (PersistConfigPool (Either c1 c2)) # runPool :: MonadUnliftIO m => Either c1 c2 -> PersistConfigBackend (Either c1 c2) m a -> PersistConfigPool (Either c1 c2) -> m a # | |
| type Rep1 (Either a :: Type -> Type) | Since: base-4.6.0.0 |
Defined in GHC.Generics type Rep1 (Either a :: Type -> Type) = D1 ('MetaData "Either" "Data.Either" "base" 'False) (C1 ('MetaCons "Left" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 a)) :+: C1 ('MetaCons "Right" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) Par1)) | |
| type Failure (Either a) | |
Defined in Basement.Monad | |
| type StM (Either e) a | |
Defined in Control.Monad.Trans.Control | |
| type Rep (Either a b) | Since: base-4.6.0.0 |
Defined in GHC.Generics type Rep (Either a b) = D1 ('MetaData "Either" "Data.Either" "base" 'False) (C1 ('MetaCons "Left" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 a)) :+: C1 ('MetaCons "Right" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 b))) | |
| type Element (Either a b) | |
Defined in Data.MonoTraversable | |
| type PersistConfigBackend (Either c1 c2) | |
Defined in Database.Persist.Class.PersistConfig | |
| type PersistConfigPool (Either c1 c2) | |
Defined in Database.Persist.Class.PersistConfig | |
class Monad m => MonadThrow (m :: Type -> Type) where #
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.
Methods
throwM :: (HasCallStack, 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
Instances
data SomeException #
The SomeException type is the root of the exception type hierarchy.
When an exception of type e is thrown, behind the scenes it is
encapsulated in a SomeException.
Constructors
| Exception e => SomeException e |
Instances
| Exception SomeException | Since: base-3.0 |
Defined in GHC.Exception.Type Methods toException :: SomeException -> SomeException # fromException :: SomeException -> Maybe SomeException # displayException :: SomeException -> String # | |
| Show SomeException | Since: base-3.0 |
Defined in GHC.Exception.Type Methods showsPrec :: Int -> SomeException -> ShowS # show :: SomeException -> String # showList :: [SomeException] -> ShowS # | |
class (Typeable e, Show e) => Exception e #
Any type that you wish to throw or catch as an exception must be an
instance of the Exception class. The simplest case is a new exception
type directly below the root:
data MyException = ThisException | ThatException
deriving Show
instance Exception MyExceptionThe default method definitions in the Exception class do what we need
in this case. You can now throw and catch ThisException and
ThatException as exceptions:
*Main> throw ThisException `catch` \e -> putStrLn ("Caught " ++ show (e :: MyException))
Caught ThisException
In more complicated examples, you may wish to define a whole hierarchy of exceptions:
---------------------------------------------------------------------
-- Make the root exception type for all the exceptions in a compiler
data SomeCompilerException = forall e . Exception e => SomeCompilerException e
instance Show SomeCompilerException where
show (SomeCompilerException e) = show e
instance Exception SomeCompilerException
compilerExceptionToException :: Exception e => e -> SomeException
compilerExceptionToException = toException . SomeCompilerException
compilerExceptionFromException :: Exception e => SomeException -> Maybe e
compilerExceptionFromException x = do
SomeCompilerException a <- fromException x
cast a
---------------------------------------------------------------------
-- Make a subhierarchy for exceptions in the frontend of the compiler
data SomeFrontendException = forall e . Exception e => SomeFrontendException e
instance Show SomeFrontendException where
show (SomeFrontendException e) = show e
instance Exception SomeFrontendException where
toException = compilerExceptionToException
fromException = compilerExceptionFromException
frontendExceptionToException :: Exception e => e -> SomeException
frontendExceptionToException = toException . SomeFrontendException
frontendExceptionFromException :: Exception e => SomeException -> Maybe e
frontendExceptionFromException x = do
SomeFrontendException a <- fromException x
cast a
---------------------------------------------------------------------
-- Make an exception type for a particular frontend compiler exception
data MismatchedParentheses = MismatchedParentheses
deriving Show
instance Exception MismatchedParentheses where
toException = frontendExceptionToException
fromException = frontendExceptionFromExceptionWe can now catch a MismatchedParentheses exception as
MismatchedParentheses, SomeFrontendException or
SomeCompilerException, but not other types, e.g. IOException:
*Main> throw MismatchedParentheses `catch` \e -> putStrLn ("Caught " ++ show (e :: MismatchedParentheses))
Caught MismatchedParentheses
*Main> throw MismatchedParentheses `catch` \e -> putStrLn ("Caught " ++ show (e :: SomeFrontendException))
Caught MismatchedParentheses
*Main> throw MismatchedParentheses `catch` \e -> putStrLn ("Caught " ++ show (e :: SomeCompilerException))
Caught MismatchedParentheses
*Main> throw MismatchedParentheses `catch` \e -> putStrLn ("Caught " ++ show (e :: IOException))
*** Exception: MismatchedParentheses
Instances
class Monad m => MonadIO (m :: Type -> Type) where #
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:
Methods
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
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
• 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(m a): liftIO
> evalStateT printState "hello" "hello" > evalStateT printState 3 3
Instances
A set of values a.
Instances
| ToJSON1 Set | |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON :: (a -> Bool) -> (a -> Value) -> ([a] -> Value) -> Set a -> Value # liftToJSONList :: (a -> Bool) -> (a -> Value) -> ([a] -> Value) -> [Set a] -> Value # liftToEncoding :: (a -> Bool) -> (a -> Encoding) -> ([a] -> Encoding) -> Set a -> Encoding # liftToEncodingList :: (a -> Bool) -> (a -> Encoding) -> ([a] -> Encoding) -> [Set a] -> Encoding # liftOmitField :: (a -> Bool) -> Set a -> Bool # | |
| Foldable Set | Folds in order of increasing key. |
Defined in Data.Set.Internal Methods fold :: Monoid m => Set m -> m # foldMap :: Monoid m => (a -> m) -> Set a -> m # foldMap' :: Monoid m => (a -> m) -> Set a -> m # foldr :: (a -> b -> b) -> b -> Set a -> b # foldr' :: (a -> b -> b) -> b -> Set a -> b # foldl :: (b -> a -> b) -> b -> Set a -> b # foldl' :: (b -> a -> b) -> b -> Set a -> b # foldr1 :: (a -> a -> a) -> Set a -> a # foldl1 :: (a -> a -> a) -> Set a -> a # elem :: Eq a => a -> Set a -> Bool # maximum :: Ord a => Set a -> a # | |
| Eq1 Set | Since: containers-0.5.9 |
| Ord1 Set | Since: containers-0.5.9 |
Defined in Data.Set.Internal | |
| Show1 Set | Since: containers-0.5.9 |
| Hashable1 Set | Since: hashable-1.3.4.0 |
Defined in Data.Hashable.Class | |
| Lift a => Lift (Set a :: Type) | Since: containers-0.6.6 |
| (Ord a, Arbitrary a) => Arbitrary (Set a) | |
| CoArbitrary a => CoArbitrary (Set a) | |
Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Set a -> Gen b -> Gen b # | |
| (Ord a, FromJSON a) => FromJSON (Set a) | |
Defined in Data.Aeson.Types.FromJSON | |
| ToJSON a => ToJSON (Set a) | |
| (Data a, Ord a) => Data (Set a) | |
Defined in Data.Set.Internal Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Set a -> c (Set a) # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Set a) # dataTypeOf :: Set a -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Set a)) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Set a)) # gmapT :: (forall b. Data b => b -> b) -> Set a -> Set a # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Set a -> r # gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Set a -> r # gmapQ :: (forall d. Data d => d -> u) -> Set a -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> Set a -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> Set a -> m (Set a) # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Set a -> m (Set a) # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Set a -> m (Set a) # | |
| Ord a => Monoid (Set a) | |
| Ord a => Semigroup (Set a) | Since: containers-0.5.7 |
| Ord a => IsList (Set a) | Since: containers-0.5.6.2 |
| (Read a, Ord a) => Read (Set a) | |
| Show a => Show (Set a) | |
| NFData a => NFData (Set a) | |
Defined in Data.Set.Internal | |
| Eq a => Eq (Set a) | |
| Ord a => Ord (Set a) | |
| Hashable v => Hashable (Set v) | Since: hashable-1.3.4.0 |
Defined in Data.Hashable.Class | |
| Ord v => GrowingAppend (Set v) | |
Defined in Data.MonoTraversable | |
| Ord e => MonoFoldable (Set e) | |
Defined in Data.MonoTraversable Methods ofoldMap :: Monoid m => (Element (Set e) -> m) -> Set e -> m # ofoldr :: (Element (Set e) -> b -> b) -> b -> Set e -> b # ofoldl' :: (a -> Element (Set e) -> a) -> a -> Set e -> a # otoList :: Set e -> [Element (Set e)] # oall :: (Element (Set e) -> Bool) -> Set e -> Bool # oany :: (Element (Set e) -> Bool) -> Set e -> Bool # ocompareLength :: Integral i => Set e -> i -> Ordering # otraverse_ :: Applicative f => (Element (Set e) -> f b) -> Set e -> f () # ofor_ :: Applicative f => Set e -> (Element (Set e) -> f b) -> f () # omapM_ :: Applicative m => (Element (Set e) -> m ()) -> Set e -> m () # oforM_ :: Applicative m => Set e -> (Element (Set e) -> m ()) -> m () # ofoldlM :: Monad m => (a -> Element (Set e) -> m a) -> a -> Set e -> m a # ofoldMap1Ex :: Semigroup m => (Element (Set e) -> m) -> Set e -> m # ofoldr1Ex :: (Element (Set e) -> Element (Set e) -> Element (Set e)) -> Set e -> Element (Set e) # ofoldl1Ex' :: (Element (Set e) -> Element (Set e) -> Element (Set e)) -> Set e -> Element (Set e) # headEx :: Set e -> Element (Set e) # lastEx :: Set e -> Element (Set e) # unsafeHead :: Set e -> Element (Set e) # unsafeLast :: Set e -> Element (Set e) # maximumByEx :: (Element (Set e) -> Element (Set e) -> Ordering) -> Set e -> Element (Set e) # minimumByEx :: (Element (Set e) -> Element (Set e) -> Ordering) -> Set e -> Element (Set e) # | |
| MonoPointed (Set a) | |
| (Ord a, PersistField a) => PersistField (Set a) | |
Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Set a -> PersistValue # fromPersistValue :: PersistValue -> Either Text (Set a) # | |
| type Item (Set a) | |
Defined in Data.Set.Internal | |
| type Element (Set e) | |
Defined in Data.MonoTraversable | |
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
Basic numeric class.
The Haskell Report defines no laws for Num. However, ( and +)( are
customarily expected to define a ring and have the following properties:*)
- Associativity of
(+) (x + y) + z=x + (y + z)- Commutativity of
(+) x + y=y + xfromInteger0x + fromInteger 0=xnegategives the additive inversex + negate x=fromInteger 0- Associativity of
(*) (x * y) * z=x * (y * z)fromInteger1x * fromInteger 1=xandfromInteger 1 * x=x- Distributivity of
(with respect to*)(+) a * (b + c)=(a * b) + (a * c)and(b + c) * a=(b * a) + (c * a)- Coherence with
toInteger - if the type also implements
Integral, thenfromIntegeris a left inverse fortoInteger, i.e.fromInteger (toInteger i) == i
Note that it isn't customarily expected that a type instance of both Num
and Ord implement an ordered ring. Indeed, in base only Integer and
Rational do.
Methods
Unary negation.
fromInteger :: Integer -> a #
Conversion from an Integer.
An integer literal represents the application of the function
fromInteger to the appropriate value of type Integer,
so such literals have type (.Num a) => a
Instances
| Num Pos | |
| Num CBool | |
| Num CChar | |
| Num CClock | |
| Num CDouble | |
| Num CFloat | |
| Num CInt | |
| Num CIntMax | |
| Num CIntPtr | |
| Num CLLong | |
| Num CLong | |
| Num CPtrdiff | |
| Num CSChar | |
| Num CSUSeconds | |
Defined in Foreign.C.Types Methods (+) :: CSUSeconds -> CSUSeconds -> CSUSeconds # (-) :: CSUSeconds -> CSUSeconds -> CSUSeconds # (*) :: CSUSeconds -> CSUSeconds -> CSUSeconds # negate :: CSUSeconds -> CSUSeconds # abs :: CSUSeconds -> CSUSeconds # signum :: CSUSeconds -> CSUSeconds # fromInteger :: Integer -> CSUSeconds # | |
| Num CShort | |
| Num CSigAtomic | |
Defined in Foreign.C.Types Methods (+) :: CSigAtomic -> CSigAtomic -> CSigAtomic # (-) :: CSigAtomic -> CSigAtomic -> CSigAtomic # (*) :: CSigAtomic -> CSigAtomic -> CSigAtomic # negate :: CSigAtomic -> CSigAtomic # abs :: CSigAtomic -> CSigAtomic # signum :: CSigAtomic -> CSigAtomic # fromInteger :: Integer -> CSigAtomic # | |
| Num CSize | |
| Num CTime | |
| Num CUChar | |
| Num CUInt | |
| Num CUIntMax | |
| Num CUIntPtr | |
| Num CULLong | |
| Num CULong | |
| Num CUSeconds | |
Defined in Foreign.C.Types | |
| Num CUShort | |
| Num CWchar | |
| Num Int16 | Since: base-2.1 |
| Num Int32 | Since: base-2.1 |
| Num Int64 | Since: base-2.1 |
| Num Int8 | Since: base-2.1 |
| Num Word16 | Since: base-2.1 |
| Num Word32 | Since: base-2.1 |
| Num Word64 | Since: base-2.1 |
| Num Word8 | Since: base-2.1 |
| Num OverflowNatural | |
Defined in Database.Persist.Class.PersistField Methods (+) :: OverflowNatural -> OverflowNatural -> OverflowNatural # (-) :: OverflowNatural -> OverflowNatural -> OverflowNatural # (*) :: OverflowNatural -> OverflowNatural -> OverflowNatural # negate :: OverflowNatural -> OverflowNatural # abs :: OverflowNatural -> OverflowNatural # signum :: OverflowNatural -> OverflowNatural # fromInteger :: Integer -> OverflowNatural # | |
| Num Scientific | WARNING: |
Defined in Data.Scientific Methods (+) :: Scientific -> Scientific -> Scientific # (-) :: Scientific -> Scientific -> Scientific # (*) :: Scientific -> Scientific -> Scientific # negate :: Scientific -> Scientific # abs :: Scientific -> Scientific # signum :: Scientific -> Scientific # fromInteger :: Integer -> Scientific # | |
| Num B | |
| Num DiffTime | |
Defined in Data.Time.Clock.Internal.DiffTime | |
| Num NominalDiffTime | |
Defined in Data.Time.Clock.Internal.NominalDiffTime Methods (+) :: NominalDiffTime -> NominalDiffTime -> NominalDiffTime # (-) :: NominalDiffTime -> NominalDiffTime -> NominalDiffTime # (*) :: NominalDiffTime -> NominalDiffTime -> NominalDiffTime # negate :: NominalDiffTime -> NominalDiffTime # abs :: NominalDiffTime -> NominalDiffTime # signum :: NominalDiffTime -> NominalDiffTime # fromInteger :: Integer -> NominalDiffTime # | |
| Num Integer | Since: base-2.1 |
| Num Natural | Note that Since: base-4.8.0.0 |
| Num Int | Since: base-2.1 |
| Num Word | Since: base-2.1 |
| RealFloat a => Num (Complex a) | Since: base-2.1 |
| Num a => Num (Identity a) | Since: base-4.9.0.0 |
Defined in Data.Functor.Identity | |
| Num a => Num (Down a) | Since: base-4.11.0.0 |
| Num a => Num (Max a) | Since: base-4.9.0.0 |
| Num a => Num (Min a) | Since: base-4.9.0.0 |
| Num a => Num (Product a) | Since: base-4.7.0.0 |
Defined in Data.Semigroup.Internal | |
| Num a => Num (Sum a) | Since: base-4.7.0.0 |
| Integral a => Num (Ratio a) | Since: base-2.0.1 |
| KnownNat n => Num (Zn n) | |
| (KnownNat n, NatWithinBound Word64 n) => Num (Zn64 n) | |
| Num (CountOf ty) | |
Defined in Basement.Types.OffsetSize | |
| Num (Offset ty) | |
Defined in Basement.Types.OffsetSize | |
| HasResolution a => Num (Fixed a) | Since: base-2.1 |
| Num a => Num (Const a b) | Since: base-4.9.0.0 |
Defined in Data.Functor.Const | |
| (Applicative f, Num a) => Num (Ap f a) | Note that even if the underlying Commutativity:
Additive inverse:
Distributivity:
Since: base-4.12.0.0 |
| Num (f a) => Num (Alt f a) | Since: base-4.8.0.0 |
| Num a => Num (Tagged s a) | |
Defined in Data.Tagged | |
class TestEquality (f :: k -> Type) where #
This class contains types where you can learn the equality of two types from information contained in terms.
The result should be Just Refl if and only if the types applied to f are
equal:
testEquality (x :: f a) (y :: f b) = Just Refl ⟺ a = b
Typically, only singleton types should inhabit this class. In that case type argument equality coincides with term equality:
testEquality (x :: f a) (y :: f b) = Just Refl ⟺ a = b ⟺ x = y
isJust (testEquality x y) = x == y
Singleton types are not required, however, and so the latter two would-be laws are not in fact valid in general.
Methods
testEquality :: forall (a :: k) (b :: k). f a -> f b -> Maybe (a :~: b) #
Conditionally prove the equality of a and b.
Instances
| TestEquality SNat | Since: base-4.18.0.0 |
Defined in GHC.TypeNats | |
| TestEquality (TypeRep :: k -> Type) | |
Defined in Data.Typeable.Internal | |
| TestEquality ((:~:) a :: k -> Type) | Since: base-4.7.0.0 |
Defined in Data.Type.Equality | |
| TestEquality ((:~~:) a :: k -> Type) | Since: base-4.10.0.0 |
Defined in Data.Type.Equality | |
| TestEquality f => TestEquality (Compose f g :: k2 -> Type) | The deduction (via generativity) that if Since: base-4.14.0.0 |
Defined in Data.Functor.Compose | |
data (a :: k1) :~~: (b :: k2) where infix 4 #
Kind heterogeneous propositional equality. Like :~:, a :~~: b is
inhabited by a terminating value if and only if a is the same type as b.
Since: base-4.10.0.0
Instances
| Category ((:~~:) :: k -> k -> Type) | Since: base-4.10.0.0 |
| TestEquality ((:~~:) a :: k -> Type) | Since: base-4.10.0.0 |
Defined in Data.Type.Equality | |
| NFData2 ((:~~:) :: Type -> Type -> Type) | Since: deepseq-1.4.3.0 |
Defined in Control.DeepSeq | |
| NFData1 ((:~~:) a :: Type -> Type) | Since: deepseq-1.4.3.0 |
Defined in Control.DeepSeq | |
| (Typeable i, Typeable j, Typeable a, Typeable b, a ~~ b) => Data (a :~~: b) | Since: base-4.10.0.0 |
Defined in Data.Data Methods gfoldl :: (forall d b0. Data d => c (d -> b0) -> d -> c b0) -> (forall g. g -> c g) -> (a :~~: b) -> c (a :~~: b) # gunfold :: (forall b0 r. Data b0 => c (b0 -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (a :~~: b) # toConstr :: (a :~~: b) -> Constr # dataTypeOf :: (a :~~: b) -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (a :~~: b)) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (a :~~: b)) # gmapT :: (forall b0. Data b0 => b0 -> b0) -> (a :~~: b) -> a :~~: b # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> (a :~~: b) -> r # gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> (a :~~: b) -> r # gmapQ :: (forall d. Data d => d -> u) -> (a :~~: b) -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> (a :~~: b) -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> (a :~~: b) -> m (a :~~: b) # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> (a :~~: b) -> m (a :~~: b) # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> (a :~~: b) -> m (a :~~: b) # | |
| a ~~ b => Bounded (a :~~: b) | Since: base-4.10.0.0 |
| a ~~ b => Enum (a :~~: b) | Since: base-4.10.0.0 |
Defined in Data.Type.Equality Methods succ :: (a :~~: b) -> a :~~: b # pred :: (a :~~: b) -> a :~~: b # fromEnum :: (a :~~: b) -> Int # enumFrom :: (a :~~: b) -> [a :~~: b] # enumFromThen :: (a :~~: b) -> (a :~~: b) -> [a :~~: b] # enumFromTo :: (a :~~: b) -> (a :~~: b) -> [a :~~: b] # enumFromThenTo :: (a :~~: b) -> (a :~~: b) -> (a :~~: b) -> [a :~~: b] # | |
| a ~~ b => Read (a :~~: b) | Since: base-4.10.0.0 |
| Show (a :~~: b) | Since: base-4.10.0.0 |
| NFData (a :~~: b) | Since: deepseq-1.4.3.0 |
Defined in Control.DeepSeq | |
| Eq (a :~~: b) | Since: base-4.10.0.0 |
| Ord (a :~~: b) | Since: base-4.10.0.0 |
data (a :: k) :~: (b :: k) where infix 4 #
Propositional equality. If a :~: b is inhabited by some terminating
value, then the type a is the same as the type b. To use this equality
in practice, pattern-match on the a :~: b to get out the Refl constructor;
in the body of the pattern-match, the compiler knows that a ~ b.
Since: base-4.7.0.0
Instances
| Category ((:~:) :: k -> k -> Type) | Since: base-4.7.0.0 |
| TestEquality ((:~:) a :: k -> Type) | Since: base-4.7.0.0 |
Defined in Data.Type.Equality | |
| NFData2 ((:~:) :: Type -> Type -> Type) | Since: deepseq-1.4.3.0 |
Defined in Control.DeepSeq | |
| NFData1 ((:~:) a) | Since: deepseq-1.4.3.0 |
Defined in Control.DeepSeq | |
| (a ~ b, Data a) => Data (a :~: b) | Since: base-4.7.0.0 |
Defined in Data.Data Methods gfoldl :: (forall d b0. Data d => c (d -> b0) -> d -> c b0) -> (forall g. g -> c g) -> (a :~: b) -> c (a :~: b) # gunfold :: (forall b0 r. Data b0 => c (b0 -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (a :~: b) # toConstr :: (a :~: b) -> Constr # dataTypeOf :: (a :~: b) -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (a :~: b)) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (a :~: b)) # gmapT :: (forall b0. Data b0 => b0 -> b0) -> (a :~: b) -> a :~: b # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> (a :~: b) -> r # gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> (a :~: b) -> r # gmapQ :: (forall d. Data d => d -> u) -> (a :~: b) -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> (a :~: b) -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> (a :~: b) -> m (a :~: b) # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> (a :~: b) -> m (a :~: b) # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> (a :~: b) -> m (a :~: b) # | |
| a ~ b => Bounded (a :~: b) | Since: base-4.7.0.0 |
| a ~ b => Enum (a :~: b) | Since: base-4.7.0.0 |
Defined in Data.Type.Equality Methods succ :: (a :~: b) -> a :~: b # pred :: (a :~: b) -> a :~: b # fromEnum :: (a :~: b) -> Int # enumFrom :: (a :~: b) -> [a :~: b] # enumFromThen :: (a :~: b) -> (a :~: b) -> [a :~: b] # enumFromTo :: (a :~: b) -> (a :~: b) -> [a :~: b] # enumFromThenTo :: (a :~: b) -> (a :~: b) -> (a :~: b) -> [a :~: b] # | |
| a ~ b => Read (a :~: b) | Since: base-4.7.0.0 |
| Show (a :~: b) | Since: base-4.7.0.0 |
| NFData (a :~: b) | Since: deepseq-1.4.3.0 |
Defined in Control.DeepSeq | |
| Eq (a :~: b) | Since: base-4.7.0.0 |
| Ord (a :~: b) | Since: base-4.7.0.0 |
Defined in Data.Type.Equality | |
Instances
| FromJSON1 Min | |
| ToJSON1 Min | |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON :: (a -> Bool) -> (a -> Value) -> ([a] -> Value) -> Min a -> Value # liftToJSONList :: (a -> Bool) -> (a -> Value) -> ([a] -> Value) -> [Min a] -> Value # liftToEncoding :: (a -> Bool) -> (a -> Encoding) -> ([a] -> Encoding) -> Min a -> Encoding # liftToEncodingList :: (a -> Bool) -> (a -> Encoding) -> ([a] -> Encoding) -> [Min a] -> Encoding # liftOmitField :: (a -> Bool) -> Min a -> Bool # | |
| MonadFix Min | Since: base-4.9.0.0 |
Defined in Data.Semigroup | |
| Foldable Min | Since: base-4.9.0.0 |
Defined in Data.Semigroup Methods fold :: Monoid m => Min m -> m # foldMap :: Monoid m => (a -> m) -> Min a -> m # foldMap' :: Monoid m => (a -> m) -> Min a -> m # foldr :: (a -> b -> b) -> b -> Min a -> b # foldr' :: (a -> b -> b) -> b -> Min a -> b # foldl :: (b -> a -> b) -> b -> Min a -> b # foldl' :: (b -> a -> b) -> b -> Min a -> b # foldr1 :: (a -> a -> a) -> Min a -> a # foldl1 :: (a -> a -> a) -> Min a -> a # elem :: Eq a => a -> Min a -> Bool # maximum :: Ord a => Min a -> a # | |
| Traversable Min | Since: base-4.9.0.0 |
| Applicative Min | Since: base-4.9.0.0 |
| Functor Min | Since: base-4.9.0.0 |
| Monad Min | Since: base-4.9.0.0 |
| NFData1 Min | Since: deepseq-1.4.3.0 |
Defined in Control.DeepSeq | |
| Generic1 Min | |
| Unbox a => Vector Vector (Min a) | |
Defined in Data.Vector.Unboxed.Base Methods basicUnsafeFreeze :: Mutable Vector s (Min a) -> ST s (Vector (Min a)) # basicUnsafeThaw :: Vector (Min a) -> ST s (Mutable Vector s (Min a)) # basicLength :: Vector (Min a) -> Int # basicUnsafeSlice :: Int -> Int -> Vector (Min a) -> Vector (Min a) # basicUnsafeIndexM :: Vector (Min a) -> Int -> Box (Min a) # basicUnsafeCopy :: Mutable Vector s (Min a) -> Vector (Min a) -> ST s () # | |
| Unbox a => MVector MVector (Min a) | |
Defined in Data.Vector.Unboxed.Base Methods basicLength :: MVector s (Min a) -> Int # basicUnsafeSlice :: Int -> Int -> MVector s (Min a) -> MVector s (Min a) # basicOverlaps :: MVector s (Min a) -> MVector s (Min a) -> Bool # basicUnsafeNew :: Int -> ST s (MVector s (Min a)) # basicInitialize :: MVector s (Min a) -> ST s () # basicUnsafeReplicate :: Int -> Min a -> ST s (MVector s (Min a)) # basicUnsafeRead :: MVector s (Min a) -> Int -> ST s (Min a) # basicUnsafeWrite :: MVector s (Min a) -> Int -> Min a -> ST s () # basicClear :: MVector s (Min a) -> ST s () # basicSet :: MVector s (Min a) -> Min a -> ST s () # basicUnsafeCopy :: MVector s (Min a) -> MVector s (Min a) -> ST s () # basicUnsafeMove :: MVector s (Min a) -> MVector s (Min a) -> ST s () # basicUnsafeGrow :: MVector s (Min a) -> Int -> ST s (MVector s (Min a)) # | |
| FromJSON a => FromJSON (Min a) | |
Defined in Data.Aeson.Types.FromJSON | |
| ToJSON a => ToJSON (Min a) | |
| Data a => Data (Min a) | Since: base-4.9.0.0 |
Defined in Data.Semigroup Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Min a -> c (Min a) # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Min a) # dataTypeOf :: Min a -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Min a)) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Min a)) # gmapT :: (forall b. Data b => b -> b) -> Min a -> Min a # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Min a -> r # gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Min a -> r # gmapQ :: (forall d. Data d => d -> u) -> Min a -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> Min a -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> Min a -> m (Min a) # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Min a -> m (Min a) # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Min a -> m (Min a) # | |
| (Ord a, Bounded a) => Monoid (Min a) | Since: base-4.9.0.0 |
| Ord a => Semigroup (Min a) | Since: base-4.9.0.0 |
| Bounded a => Bounded (Min a) | Since: base-4.9.0.0 |
| Enum a => Enum (Min a) | Since: base-4.9.0.0 |
| Generic (Min a) | |
| Num a => Num (Min a) | Since: base-4.9.0.0 |
| Read a => Read (Min a) | Since: base-4.9.0.0 |
| Show a => Show (Min a) | Since: base-4.9.0.0 |
| NFData a => NFData (Min a) | Since: deepseq-1.4.2.0 |
Defined in Control.DeepSeq | |
| Eq a => Eq (Min a) | Since: base-4.9.0.0 |
| Ord a => Ord (Min a) | Since: base-4.9.0.0 |
| Hashable a => Hashable (Min a) | |
Defined in Data.Hashable.Class | |
| Unbox a => Unbox (Min a) | |
Defined in Data.Vector.Unboxed.Base | |
| type Rep1 Min | Since: base-4.9.0.0 |
Defined in Data.Semigroup | |
| newtype MVector s (Min a) | |
Defined in Data.Vector.Unboxed.Base | |
| type Rep (Min a) | Since: base-4.9.0.0 |
Defined in Data.Semigroup | |
| newtype Vector (Min a) | |
Defined in Data.Vector.Unboxed.Base | |
newtype IdentityT (f :: k -> Type) (a :: k) #
The trivial monad transformer, which maps a monad to an equivalent monad.
Constructors
| IdentityT | |
Fields
| |
Instances
class (forall (m :: Type -> Type). Monad m => Monad (t m)) => MonadTrans (t :: (Type -> Type) -> Type -> Type) where #
The class of monad transformers.
For any monad m, the result t m should also be a monad,
and lift should be a monad transformation from m to t m,
i.e. it should satisfy the following laws:
Since 0.6.0.0 and for GHC 8.6 and later, the requirement that t m
be a Monad is enforced by the implication constraint
forall m. enabled by the
Monad m => Monad (t m)QuantifiedConstraints extension.
Ambiguity error with GHC 9.0 to 9.2.2
These versions of GHC have a bug (https://gitlab.haskell.org/ghc/ghc/-/issues/20582) which causes constraints like
(MonadTrans t, forall m. Monad m => Monad (t m)) => ...
to be reported as ambiguous. For transformers 0.6 and later, this can be fixed by removing the second constraint, which is implied by the first.
Methods
lift :: Monad m => m a -> t m a #
Lift a computation from the argument monad to the constructed monad.
Instances
data ReaderT r (m :: Type -> Type) a #
The reader monad transformer, which adds a read-only environment to the given monad.
The return function ignores the environment, while >>= passes
the inherited environment to both subcomputations.
Instances
General-purpose finite sequences.
Instances
| Arbitrary1 Seq | |
Defined in Test.QuickCheck.Arbitrary | |
| FromJSON1 Seq | |
| ToJSON1 Seq | |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON :: (a -> Bool) -> (a -> Value) -> ([a] -> Value) -> Seq a -> Value # liftToJSONList :: (a -> Bool) -> (a -> Value) -> ([a] -> Value) -> [Seq a] -> Value # liftToEncoding :: (a -> Bool) -> (a -> Encoding) -> ([a] -> Encoding) -> Seq a -> Encoding # liftToEncodingList :: (a -> Bool) -> (a -> Encoding) -> ([a] -> Encoding) -> [Seq a] -> Encoding # liftOmitField :: (a -> Bool) -> Seq a -> Bool # | |
| MonadFix Seq | Since: containers-0.5.11 |
Defined in Data.Sequence.Internal | |
| MonadZip Seq |
|
| Foldable Seq | |
Defined in Data.Sequence.Internal Methods fold :: Monoid m => Seq m -> m # foldMap :: Monoid m => (a -> m) -> Seq a -> m # foldMap' :: Monoid m => (a -> m) -> Seq a -> m # foldr :: (a -> b -> b) -> b -> Seq a -> b # foldr' :: (a -> b -> b) -> b -> Seq a -> b # foldl :: (b -> a -> b) -> b -> Seq a -> b # foldl' :: (b -> a -> b) -> b -> Seq a -> b # foldr1 :: (a -> a -> a) -> Seq a -> a # foldl1 :: (a -> a -> a) -> Seq a -> a # elem :: Eq a => a -> Seq a -> Bool # maximum :: Ord a => Seq a -> a # | |
| Eq1 Seq | Since: containers-0.5.9 |
| Ord1 Seq | Since: containers-0.5.9 |
Defined in Data.Sequence.Internal | |
| Read1 Seq | Since: containers-0.5.9 |
Defined in Data.Sequence.Internal | |
| Show1 Seq | Since: containers-0.5.9 |
| Traversable Seq | |
| Alternative Seq | Since: containers-0.5.4 |
| Applicative Seq | Since: containers-0.5.4 |
| Functor Seq | |
| Monad Seq | |
| MonadPlus Seq | |
| UnzipWith Seq | |
Defined in Data.Sequence.Internal Methods unzipWith' :: (x -> (a, b)) -> Seq x -> (Seq a, Seq b) | |
| Hashable1 Seq | Since: hashable-1.3.4.0 |
Defined in Data.Hashable.Class | |
| Lift a => Lift (Seq a :: Type) | Since: containers-0.6.6 |
| Arbitrary a => Arbitrary (Seq a) | |
| CoArbitrary a => CoArbitrary (Seq a) | |
Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Seq a -> Gen b -> Gen b # | |
| FromJSON a => FromJSON (Seq a) | |
Defined in Data.Aeson.Types.FromJSON | |
| ToJSON a => ToJSON (Seq a) | |
| Data a => Data (Seq a) | |
Defined in Data.Sequence.Internal Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Seq a -> c (Seq a) # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Seq a) # dataTypeOf :: Seq a -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Seq a)) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Seq a)) # gmapT :: (forall b. Data b => b -> b) -> Seq a -> Seq a # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Seq a -> r # gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Seq a -> r # gmapQ :: (forall d. Data d => d -> u) -> Seq a -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> Seq a -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> Seq a -> m (Seq a) # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Seq a -> m (Seq a) # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Seq a -> m (Seq a) # | |
| a ~ Char => IsString (Seq a) | Since: containers-0.5.7 |
Defined in Data.Sequence.Internal Methods fromString :: String -> Seq a # | |
| Monoid (Seq a) | |
| Semigroup (Seq a) | Since: containers-0.5.7 |
| IsList (Seq a) | |
| Read a => Read (Seq a) | |
| Show a => Show (Seq a) | |
| NFData a => NFData (Seq a) | |
Defined in Data.Sequence.Internal | |
| Eq a => Eq (Seq a) | |
| Ord a => Ord (Seq a) | |
| Hashable v => Hashable (Seq v) | Since: hashable-1.3.4.0 |
Defined in Data.Hashable.Class | |
| GrowingAppend (Seq a) | |
Defined in Data.MonoTraversable | |
| MonoFoldable (Seq a) | |
Defined in Data.MonoTraversable Methods ofoldMap :: Monoid m => (Element (Seq a) -> m) -> Seq a -> m # ofoldr :: (Element (Seq a) -> b -> b) -> b -> Seq a -> b # ofoldl' :: (a0 -> Element (Seq a) -> a0) -> a0 -> Seq a -> a0 # otoList :: Seq a -> [Element (Seq a)] # oall :: (Element (Seq a) -> Bool) -> Seq a -> Bool # oany :: (Element (Seq a) -> Bool) -> Seq a -> Bool # ocompareLength :: Integral i => Seq a -> i -> Ordering # otraverse_ :: Applicative f => (Element (Seq a) -> f b) -> Seq a -> f () # ofor_ :: Applicative f => Seq a -> (Element (Seq a) -> f b) -> f () # omapM_ :: Applicative m => (Element (Seq a) -> m ()) -> Seq a -> m () # oforM_ :: Applicative m => Seq a -> (Element (Seq a) -> m ()) -> m () # ofoldlM :: Monad m => (a0 -> Element (Seq a) -> m a0) -> a0 -> Seq a -> m a0 # ofoldMap1Ex :: Semigroup m => (Element (Seq a) -> m) -> Seq a -> m # ofoldr1Ex :: (Element (Seq a) -> Element (Seq a) -> Element (Seq a)) -> Seq a -> Element (Seq a) # ofoldl1Ex' :: (Element (Seq a) -> Element (Seq a) -> Element (Seq a)) -> Seq a -> Element (Seq a) # headEx :: Seq a -> Element (Seq a) # lastEx :: Seq a -> Element (Seq a) # unsafeHead :: Seq a -> Element (Seq a) # unsafeLast :: Seq a -> Element (Seq a) # maximumByEx :: (Element (Seq a) -> Element (Seq a) -> Ordering) -> Seq a -> Element (Seq a) # minimumByEx :: (Element (Seq a) -> Element (Seq a) -> Ordering) -> Seq a -> Element (Seq a) # | |
| MonoFunctor (Seq a) | |
| MonoPointed (Seq a) | |
| MonoTraversable (Seq a) | |
| IsSequence (Seq a) | |
Defined in Data.Sequences Methods fromList :: [Element (Seq a)] -> Seq a # lengthIndex :: Seq a -> Index (Seq a) # break :: (Element (Seq a) -> Bool) -> Seq a -> (Seq a, Seq a) # span :: (Element (Seq a) -> Bool) -> Seq a -> (Seq a, Seq a) # dropWhile :: (Element (Seq a) -> Bool) -> Seq a -> Seq a # takeWhile :: (Element (Seq a) -> Bool) -> Seq a -> Seq a # splitAt :: Index (Seq a) -> Seq a -> (Seq a, Seq a) # unsafeSplitAt :: Index (Seq a) -> Seq a -> (Seq a, Seq a) # take :: Index (Seq a) -> Seq a -> Seq a # unsafeTake :: Index (Seq a) -> Seq a -> Seq a # drop :: Index (Seq a) -> Seq a -> Seq a # unsafeDrop :: Index (Seq a) -> Seq a -> Seq a # dropEnd :: Index (Seq a) -> Seq a -> Seq a # partition :: (Element (Seq a) -> Bool) -> Seq a -> (Seq a, Seq a) # uncons :: Seq a -> Maybe (Element (Seq a), Seq a) # unsnoc :: Seq a -> Maybe (Seq a, Element (Seq a)) # filter :: (Element (Seq a) -> Bool) -> Seq a -> Seq a # filterM :: Monad m => (Element (Seq a) -> m Bool) -> Seq a -> m (Seq a) # replicate :: Index (Seq a) -> Element (Seq a) -> Seq a # replicateM :: Monad m => Index (Seq a) -> m (Element (Seq a)) -> m (Seq a) # groupBy :: (Element (Seq a) -> Element (Seq a) -> Bool) -> Seq a -> [Seq a] # groupAllOn :: Eq b => (Element (Seq a) -> b) -> Seq a -> [Seq a] # subsequences :: Seq a -> [Seq a] # permutations :: Seq a -> [Seq a] # tailMay :: Seq a -> Maybe (Seq a) # initMay :: Seq a -> Maybe (Seq a) # unsafeTail :: Seq a -> Seq a # unsafeInit :: Seq a -> Seq a # index :: Seq a -> Index (Seq a) -> Maybe (Element (Seq a)) # indexEx :: Seq a -> Index (Seq a) -> Element (Seq a) # unsafeIndex :: Seq a -> Index (Seq a) -> Element (Seq a) # splitWhen :: (Element (Seq a) -> Bool) -> Seq a -> [Seq a] # | |
| SemiSequence (Seq a) | |
| type Item (Seq a) | |
Defined in Data.Sequence.Internal | |
| type Element (Seq a) | |
Defined in Data.MonoTraversable | |
| type Index (Seq a) | |
Defined in Data.Sequences | |
data GenericArbitrary a #
Newtype for DerivingVia
Usage:
data Foo = Foo
{ _fooX :: X
, _fooY :: Y
} deriving (Generic)
deriving (Arbitrary) via GenericArbitrary Foo
Since: generic-arbitrary-1.0.0
Instances
| (Generic a, GArbitrary a (Rep a) some, RecursivelyShrink (Rep a), GSubterms (Rep a) a) => Arbitrary (GenericArbitrary a) | |
Defined in Test.QuickCheck.Arbitrary.Generic Methods arbitrary :: Gen (GenericArbitrary a) # shrink :: GenericArbitrary a -> [GenericArbitrary a] # | |
| Show a => Show (GenericArbitrary a) | |
Defined in Test.QuickCheck.Arbitrary.Generic Methods showsPrec :: Int -> GenericArbitrary a -> ShowS # show :: GenericArbitrary a -> String # showList :: [GenericArbitrary a] -> ShowS # | |
| Eq a => Eq (GenericArbitrary a) | |
Defined in Test.QuickCheck.Arbitrary.Generic Methods (==) :: GenericArbitrary a -> GenericArbitrary a -> Bool # (/=) :: GenericArbitrary a -> GenericArbitrary a -> Bool # | |
class Monad m => MonadError e (m :: Type -> Type) | m -> e where #
The strategy of combining computations that can throw exceptions by bypassing bound functions from the point an exception is thrown to the point that it is handled.
Is parameterized over the type of error information and
the monad type constructor.
It is common to use Either StringMonadError class.
You can also define your own error type and/or use a monad type constructor
other than Either StringEither IOErrorMonadError
class.
(If you are using the deprecated Control.Monad.Error or
Control.Monad.Trans.Error, you may also have to define an Error instance.)
Minimal complete definition
Instances
($) :: forall (r :: RuntimeRep) a (b :: TYPE r). (a -> b) -> a -> b infixr 0 #
Application operator. This operator is redundant, since ordinary
application (f x) means the same as (f . However, $ x)$ has
low, right-associative binding precedence, so it sometimes allows
parentheses to be omitted; for example:
f $ g $ h x = f (g (h x))
It is also useful in higher-order situations, such as map ($ 0) xszipWith ($) fs xs
Note that ( is representation-polymorphic in its result type, so that
$)foo where $ Truefoo :: Bool -> Int# is well-typed.
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 bssdo expression
do bs <- bss bs
Examples
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
(<>) :: Semigroup a => a -> a -> a infixr 6 #
An associative operation.
>>>[1,2,3] <> [4,5,6][1,2,3,4,5,6]
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
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
minimum :: (Foldable t, Ord a) => t a -> a #
The least element of a non-empty structure.
This function is non-total and will raise a runtime exception if the structure happens to be empty. A structure that supports random access and maintains its elements in order should provide a specialised implementation to return the minimum in faster than linear time.
Examples
Basic usage:
>>>minimum [1..10]1
>>>minimum []*** Exception: Prelude.minimum: empty list
>>>minimum Nothing*** Exception: minimum: empty structure
WARNING: This function is partial for possibly-empty structures like lists.
Since: base-4.8.0.0
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
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"
genericShrink :: (Generic a, RecursivelyShrink (Rep a), GSubterms (Rep a) a) => a -> [a] #
Shrink a term to any of its immediate subterms, and also recursively shrink all subterms.
apply :: forall {k1} {k2} (f :: k1 -> k2) (g :: k1 -> k2) (a :: k1) (b :: k1). (f :~: g) -> (a :~: b) -> f a :~: g b #
Apply one equality to another, respectively
fromIntegral :: (Integral a, Num b) => a -> b #
General coercion from Integral types.
WARNING: This function performs silent truncation if the result type is not at least as big as the argument's type.
empty :: Alternative f => f a #
The identity of <|>
(<|>) :: Alternative f => f a -> f a -> f a infixl 3 #
An associative binary operation
filter :: (a -> Bool) -> [a] -> [a] #
\(\mathcal{O}(n)\). filter, applied to a predicate and a list, returns
the list of those elements that satisfy the predicate; i.e.,
filter p xs = [ x | x <- xs, p x]
>>>filter odd [1, 2, 3][1,3]
Case analysis for the Bool type. bool x y px
when p is False, and evaluates to y when p is True.
This is equivalent to if p then y else x; that is, one can
think of it as an if-then-else construct with its arguments
reordered.
Examples
Basic usage:
>>>bool "foo" "bar" True"bar">>>bool "foo" "bar" False"foo"
Confirm that bool x y pif p then y else x are
equivalent:
>>>let p = True; x = "bar"; y = "foo">>>bool x y p == if p then y else xTrue>>>let p = False>>>bool x y p == if p then y else xTrue
Since: base-4.7.0.0
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.
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
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
catMaybes :: [Maybe a] -> [a] #
The catMaybes function takes a list of Maybes and returns
a list of all the Just values.
Examples
Basic usage:
>>>catMaybes [Just 1, Nothing, Just 3][1,3]
When constructing a list of Maybe values, catMaybes can be used
to return all of the "success" results (if the list is the result
of a map, then mapMaybe would be more appropriate):
>>>import Text.Read ( readMaybe )>>>[readMaybe x :: Maybe Int | x <- ["1", "Foo", "3"] ][Just 1,Nothing,Just 3]>>>catMaybes $ [readMaybe x :: Maybe Int | x <- ["1", "Foo", "3"] ][1,3]
($>) :: Functor f => f a -> b -> f b infixl 4 #
Flipped version of <$.
Examples
Replace the contents of a Maybe IntString:
>>>Nothing $> "foo"Nothing>>>Just 90210 $> "foo"Just "foo"
Replace the contents of an Either Int IntString, resulting in an Either
Int String
>>>Left 8675309 $> "foo"Left 8675309>>>Right 8675309 $> "foo"Right "foo"
Replace each element of a list with a constant String:
>>>[1,2,3] $> "foo"["foo","foo","foo"]
Replace the second element of a pair with a constant String:
>>>(1,2) $> "foo"(1,"foo")
Since: base-4.7.0.0
void :: Functor f => f a -> f () #
void valueIO action.
Examples
Replace the contents of a Maybe Int
>>>void NothingNothing>>>void (Just 3)Just ()
Replace the contents of an Either Int IntEither Int ()
>>>void (Left 8675309)Left 8675309>>>void (Right 8675309)Right ()
Replace every element of a list with unit:
>>>void [1,2,3][(),(),()]
Replace the second element of a pair with unit:
>>>void (1,2)(1,())
Discard the result of an IO action:
>>>mapM print [1,2]1 2 [(),()]>>>void $ mapM print [1,2]1 2
unless :: Applicative f => Bool -> f () -> f () #
The reverse of when.
(<$>) :: Functor f => (a -> b) -> f a -> f b infixl 4 #
An infix synonym for fmap.
The name of this operator is an allusion to $.
Note the similarities between their types:
($) :: (a -> b) -> a -> b (<$>) :: Functor f => (a -> b) -> f a -> f b
Whereas $ is function application, <$> is function
application lifted over a Functor.
Examples
Convert from a Maybe IntMaybe
Stringshow:
>>>show <$> NothingNothing>>>show <$> Just 3Just "3"
Convert from an Either Int IntEither IntString using show:
>>>show <$> Left 17Left 17>>>show <$> Right 17Right "17"
Double each element of a list:
>>>(*2) <$> [1,2,3][2,4,6]
Apply even to the second element of a pair:
>>>even <$> (2,2)(2,True)
guard :: Alternative f => Bool -> f () #
Conditional failure of Alternative computations. Defined by
guard True =pure() guard False =empty
Examples
Common uses of guard include conditionally signaling an error in
an error monad and conditionally rejecting the current choice in an
Alternative-based parser.
As an example of signaling an error in the error monad Maybe,
consider a safe division function safeDiv x y that returns
Nothing when the denominator y is zero and Just (x `div`
y)
>>>safeDiv 4 0Nothing
>>>safeDiv 4 2Just 2
A definition of safeDiv using guards, but not guard:
safeDiv :: Int -> Int -> Maybe Int
safeDiv x y | y /= 0 = Just (x `div` y)
| otherwise = Nothing
A definition of safeDiv using guard and Monad do-notation:
safeDiv :: Int -> Int -> Maybe Int safeDiv x y = do guard (y /= 0) return (x `div` y)
throwWithCallStack :: (HasCallStack, MonadThrow m, Exception e) => e -> m a #
Attaches the CallStack to the AnnotatedException that is thrown.
Since: annotated-exception-0.1.0.0
checkpointCallStack :: (MonadCatch m, HasCallStack) => m a -> m a #
const x y always evaluates to x, ignoring its second argument.
>>>const 42 "hello"42
>>>map (const 42) [0..3][42,42,42,42]
readMaybe :: Read a => String -> Maybe a #
Parse a string using the Read instance.
Succeeds if there is exactly one valid result.
>>>readMaybe "123" :: Maybe IntJust 123
>>>readMaybe "hello" :: Maybe IntNothing
Since: base-4.6.0.0
uncurry :: (a -> b -> c) -> (a, b) -> c #
uncurry converts a curried function to a function on pairs.
Examples
>>>uncurry (+) (1,2)3
>>>uncurry ($) (show, 1)"1"
>>>map (uncurry max) [(1,2), (3,4), (6,8)][2,4,8]
for :: (Traversable t, Applicative f) => t a -> (a -> f b) -> f (t b) #
concat :: Foldable t => t [a] -> [a] #
The concatenation of all the elements of a container of lists.
Examples
Basic usage:
>>>concat (Just [1, 2, 3])[1,2,3]
>>>concat (Left 42)[]
>>>concat [[1, 2, 3], [4, 5], [6], []][1,2,3,4,5,6]
(>>>) :: 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
(=<<) :: Monad m => (a -> m b) -> m a -> m b infixr 1 #
Same as >>=, but with the arguments interchanged.
flip :: (a -> b -> c) -> b -> a -> c #
flip ff.
>>>flip (++) "hello" "world""worldhello"
($!) :: forall (r :: RuntimeRep) a (b :: TYPE r). (a -> b) -> a -> b infixr 0 #
Strict (call-by-value) application operator. It takes a function and an argument, evaluates the argument to weak head normal form (WHNF), then calls the function with that value.
maybe :: b -> (a -> b) -> Maybe a -> b #
The maybe function takes a default value, a function, and a Maybe
value. If the Maybe value is Nothing, the function returns the
default value. Otherwise, it applies the function to the value inside
the Just and returns the result.
Examples
Basic usage:
>>>maybe False odd (Just 3)True
>>>maybe False odd NothingFalse
Read an integer from a string using readMaybe. If we succeed,
return twice the integer; that is, apply (*2) to it. If instead
we fail to parse an integer, return 0 by default:
>>>import Text.Read ( readMaybe )>>>maybe 0 (*2) (readMaybe "5")10>>>maybe 0 (*2) (readMaybe "")0
Apply show to a Maybe Int. If we have Just n, we want to show
the underlying Int n. But if we have Nothing, we return the
empty string instead of (for example) "Nothing":
>>>maybe "" show (Just 5)"5">>>maybe "" show Nothing""
all :: Foldable t => (a -> Bool) -> t a -> Bool #
Determines whether all elements of the structure satisfy the predicate.
Examples
Basic usage:
>>>all (> 3) []True
>>>all (> 3) [1,2]False
>>>all (> 3) [1,2,3,4,5]False
>>>all (> 3) [1..]False
>>>all (> 3) [4..]* Hangs forever *
concatMap :: Foldable t => (a -> [b]) -> t a -> [b] #
Map a function over all the elements of a container and concatenate the resulting lists.
Examples
Basic usage:
>>>concatMap (take 3) [[1..], [10..], [100..], [1000..]][1,2,3,10,11,12,100,101,102,1000,1001,1002]
>>>concatMap (take 3) (Just [1..])[1,2,3]
(/) :: Fractional a => a -> a -> a infixl 7 #
Fractional division.
either :: (a -> c) -> (b -> c) -> Either a b -> c #
Case analysis for the Either type.
If the value is Left aa;
if it is Right bb.
Examples
We create two values of type Either String IntLeft constructor and another using the Right constructor. Then
we apply "either" the length function (if we have a String)
or the "times-two" function (if we have an Int):
>>>let s = Left "foo" :: Either String Int>>>let n = Right 3 :: Either String Int>>>either length (*2) s3>>>either length (*2) n6
fromRight :: b -> Either a b -> b #
Return the contents of a Right-value or a default value otherwise.
Examples
Basic usage:
>>>fromRight 1 (Right 3)3>>>fromRight 1 (Left "foo")1
Since: base-4.10.0.0
trans :: forall {k} (a :: k) (b :: k) (c :: k). (a :~: b) -> (b :~: c) -> a :~: c #
Transitivity of equality
gcastWith :: forall {k} (a :: k) (b :: k) r. (a :~: b) -> (a ~ b => r) -> r #
Generalized form of type-safe cast using propositional equality
inner :: forall {k1} {k2} (f :: k1 -> k2) (a :: k1) (g :: k1 -> k2) (b :: k1). (f a :~: g b) -> a :~: b #
Extract equality of the arguments from an equality of applied types
outer :: forall {k1} {k2} (f :: k1 -> k2) (a :: k1) (g :: k1 -> k2) (b :: k1). (f a :~: g b) -> f :~: g #
Extract equality of type constructors from an equality of applied types
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
Basic usage:
>>>traverse_ print ["Hello", "world", "!"]"Hello" "world" "!"
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
Basic usage:
>>>for_ [1..4] print1 2 3 4
(>=>) :: Monad m => (a -> m b) -> (b -> m c) -> a -> m c infixr 1 #
Left-to-right composition of Kleisli arrows.
'(bs ' can be understood as the >=> cs) ado expression
do b <- bs a cs b
replicateM :: Applicative m => Int -> m a -> m [a] #
replicateM n actact n times,
and then returns the list of results:
Examples
>>>import Control.Monad.State>>>runState (replicateM 3 $ state $ \s -> (s, s + 1)) 1([1,2,3],4)
replicateM_ :: Applicative m => Int -> m a -> m () #
genericArbitrary :: forall a (ga :: Type -> Type) (some :: Bool). (Generic a, GArbitrary a ga some, ga ~ Rep a) => Gen a #