Safe Haskell | Safe-Inferred |
---|---|
Language | Haskell2010 |
Documentation
Proxy
is a type that holds no data, but has a phantom parameter of
arbitrary type (or even kind). Its use is to provide type information, even
though there is no value available of that type (or it may be too costly to
create one).
Historically,
is a safer alternative to the
Proxy
::
Proxy
a
idiom.
undefined
:: a
>>>
Proxy :: Proxy (Void, Int -> Int)
Proxy
Proxy can even hold types of higher kinds,
>>>
Proxy :: Proxy Either
Proxy
>>>
Proxy :: Proxy Functor
Proxy
>>>
Proxy :: Proxy complicatedStructure
Proxy
Instances
Generic1 ( Proxy :: k -> Type ) |
Since: base-4.6.0.0 |
Monad ( Proxy :: Type -> Type ) |
Since: base-4.7.0.0 |
Functor ( Proxy :: Type -> Type ) |
Since: base-4.7.0.0 |
Applicative ( Proxy :: Type -> Type ) |
Since: base-4.7.0.0 |
Foldable ( Proxy :: Type -> Type ) |
Since: base-4.7.0.0 |
Defined in Data.Foldable fold :: Monoid m => Proxy m -> m Source # foldMap :: Monoid m => (a -> m) -> Proxy a -> m Source # foldMap' :: Monoid m => (a -> m) -> Proxy a -> m Source # foldr :: (a -> b -> b) -> b -> Proxy a -> b Source # foldr' :: (a -> b -> b) -> b -> Proxy a -> b Source # foldl :: (b -> a -> b) -> b -> Proxy a -> b Source # foldl' :: (b -> a -> b) -> b -> Proxy a -> b Source # foldr1 :: (a -> a -> a) -> Proxy a -> a Source # foldl1 :: (a -> a -> a) -> Proxy a -> a Source # toList :: Proxy a -> [a] Source # null :: Proxy a -> Bool Source # length :: Proxy a -> Int Source # elem :: Eq a => a -> Proxy a -> Bool Source # maximum :: Ord a => Proxy a -> a Source # minimum :: Ord a => Proxy a -> a Source # |
|
Traversable ( Proxy :: Type -> Type ) |
Since: base-4.7.0.0 |
MonadPlus ( Proxy :: Type -> Type ) |
Since: base-4.9.0.0 |
Alternative ( Proxy :: Type -> Type ) |
Since: base-4.9.0.0 |
Contravariant ( Proxy :: Type -> Type ) | |
Eq1 ( Proxy :: Type -> Type ) |
Since: base-4.9.0.0 |
Ord1 ( Proxy :: Type -> Type ) |
Since: base-4.9.0.0 |
Defined in Data.Functor.Classes |
|
Read1 ( Proxy :: Type -> Type ) |
Since: base-4.9.0.0 |
Defined in Data.Functor.Classes liftReadsPrec :: ( Int -> ReadS a) -> ReadS [a] -> Int -> ReadS ( Proxy a) Source # liftReadList :: ( Int -> ReadS a) -> ReadS [a] -> ReadS [ Proxy a] Source # liftReadPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec ( Proxy a) Source # liftReadListPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec [ Proxy a] Source # |
|
Show1 ( Proxy :: Type -> Type ) |
Since: base-4.9.0.0 |
Hashable1 ( Proxy :: Type -> Type ) | |
Defined in Data.Hashable.Class |
|
Bounded ( Proxy t) |
Since: base-4.7.0.0 |
Enum ( Proxy s) |
Since: base-4.7.0.0 |
Defined in Data.Proxy succ :: Proxy s -> Proxy s Source # pred :: Proxy s -> Proxy s Source # toEnum :: Int -> Proxy s Source # fromEnum :: Proxy s -> Int Source # enumFrom :: Proxy s -> [ Proxy s] Source # enumFromThen :: Proxy s -> Proxy s -> [ Proxy s] Source # enumFromTo :: Proxy s -> Proxy s -> [ Proxy s] Source # enumFromThenTo :: Proxy s -> Proxy s -> Proxy s -> [ Proxy s] Source # |
|
Eq ( Proxy s) |
Since: base-4.7.0.0 |
Ord ( Proxy s) |
Since: base-4.7.0.0 |
Read ( Proxy t) |
Since: base-4.7.0.0 |
Show ( Proxy s) |
Since: base-4.7.0.0 |
Ix ( Proxy s) |
Since: base-4.7.0.0 |
Generic ( Proxy t) |
Since: base-4.6.0.0 |
Semigroup ( Proxy s) |
Since: base-4.9.0.0 |
Monoid ( Proxy s) |
Since: base-4.7.0.0 |
Hashable ( Proxy a) | |
type Rep1 ( Proxy :: k -> Type ) | |
type Rep ( Proxy t) | |