base-4.9.0.0: Basic libraries

Copyright(c) The University of Glasgow, CWI 2001--2004
LicenseBSD-style (see the file libraries/base/LICENSE)
Maintainerlibraries@haskell.org
Stabilityexperimental
Portabilityportable
Safe HaskellTrustworthy
LanguageHaskell2010

Data.Typeable

Contents

Description

The Typeable class reifies types to some extent by associating type representations to types. These type representations can be compared, and one can in turn define a type-safe cast operation. To this end, an unsafe cast is guarded by a test for type (representation) equivalence. The module Data.Dynamic uses Typeable for an implementation of dynamics. The module Data.Data uses Typeable and type-safe cast (but not dynamics) to support the "Scrap your boilerplate" style of generic programming.

Compatibility Notes

Since GHC 7.8, Typeable is poly-kinded. The changes required for this might break some old programs involving Typeable. More details on this, including how to fix your code, can be found on the PolyTypeable wiki page

Synopsis

The Typeable class

class Typeable a Source #

The class Typeable allows a concrete representation of a type to be calculated.

Minimal complete definition

typeRep#

typeRep :: forall proxy a. Typeable a => proxy a -> TypeRep Source #

Takes a value of type a and returns a concrete representation of that type.

Since: 4.7.0.0

Propositional equality

data a :~: b where infix 4 Source #

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: 4.7.0.0

Constructors

Refl :: a :~: a 

Instances

Category k ((:~:) k) Source # 

Methods

id :: cat a a Source #

(.) :: cat b c -> cat a b -> cat a c Source #

TestEquality k ((:~:) k a) Source # 

Methods

testEquality :: f a -> f b -> Maybe (((k :~: a) :~: a) b) Source #

TestCoercion k ((:~:) k a) Source # 

Methods

testCoercion :: f a -> f b -> Maybe (Coercion (k :~: a) a b) Source #

(~) k a b => Bounded ((:~:) k a b) Source # 

Methods

minBound :: (k :~: a) b Source #

maxBound :: (k :~: a) b Source #

(~) k a b => Enum ((:~:) k a b) Source # 

Methods

succ :: (k :~: a) b -> (k :~: a) b Source #

pred :: (k :~: a) b -> (k :~: a) b Source #

toEnum :: Int -> (k :~: a) b Source #

fromEnum :: (k :~: a) b -> Int Source #

enumFrom :: (k :~: a) b -> [(k :~: a) b] Source #

enumFromThen :: (k :~: a) b -> (k :~: a) b -> [(k :~: a) b] Source #

enumFromTo :: (k :~: a) b -> (k :~: a) b -> [(k :~: a) b] Source #

enumFromThenTo :: (k :~: a) b -> (k :~: a) b -> (k :~: a) b -> [(k :~: a) b] Source #

Eq ((:~:) k a b) Source # 

Methods

(==) :: (k :~: a) b -> (k :~: a) b -> Bool #

(/=) :: (k :~: a) b -> (k :~: a) b -> Bool #

((~) * a b, Data a) => Data ((:~:) * a b) Source # 

Methods

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

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

toConstr :: (* :~: a) b -> Constr Source #

dataTypeOf :: (* :~: a) b -> DataType Source #

dataCast1 :: Typeable (* -> *) t => (forall d. Data d => c (t d)) -> Maybe (c ((* :~: a) b)) Source #

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

gmapT :: (forall c. Data c => c -> c) -> (* :~: a) b -> (* :~: a) b Source #

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> (* :~: a) b -> r Source #

gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> (* :~: a) b -> r Source #

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

gmapQi :: Int -> (forall d. Data d => d -> u) -> (* :~: a) b -> u Source #

gmapM :: Monad m => (forall d. Data d => d -> m d) -> (* :~: a) b -> m ((* :~: a) b) Source #

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> (* :~: a) b -> m ((* :~: a) b) Source #

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> (* :~: a) b -> m ((* :~: a) b) Source #

Ord ((:~:) k a b) Source # 

Methods

compare :: (k :~: a) b -> (k :~: a) b -> Ordering #

(<) :: (k :~: a) b -> (k :~: a) b -> Bool #

(<=) :: (k :~: a) b -> (k :~: a) b -> Bool #

(>) :: (k :~: a) b -> (k :~: a) b -> Bool #

(>=) :: (k :~: a) b -> (k :~: a) b -> Bool #

max :: (k :~: a) b -> (k :~: a) b -> (k :~: a) b #

min :: (k :~: a) b -> (k :~: a) b -> (k :~: a) b #

(~) k a b => Read ((:~:) k a b) Source # 

Methods

readsPrec :: Int -> ReadS ((k :~: a) b) Source #

readList :: ReadS [(k :~: a) b] Source #

readPrec :: ReadPrec ((k :~: a) b) Source #

readListPrec :: ReadPrec [(k :~: a) b] Source #

Show ((:~:) k a b) Source # 

Methods

showsPrec :: Int -> (k :~: a) b -> ShowS Source #

show :: (k :~: a) b -> String Source #

showList :: [(k :~: a) b] -> ShowS Source #

For backwards compatibility

typeOf :: forall a. Typeable a => a -> TypeRep Source #

typeOf1 :: forall t a. Typeable t => t a -> TypeRep Source #

typeOf2 :: forall t a b. Typeable t => t a b -> TypeRep Source #

typeOf3 :: forall t a b c. Typeable t => t a b c -> TypeRep Source #

typeOf4 :: forall t a b c d. Typeable t => t a b c d -> TypeRep Source #

typeOf5 :: forall t a b c d e. Typeable t => t a b c d e -> TypeRep Source #

typeOf6 :: forall t a b c d e f. Typeable t => t a b c d e f -> TypeRep Source #

typeOf7 :: forall t a b c d e f g. Typeable t => t a b c d e f g -> TypeRep Source #

type Typeable1 a = Typeable a Source #

Deprecated: renamed to Typeable

type Typeable2 a = Typeable a Source #

Deprecated: renamed to Typeable

type Typeable3 a = Typeable a Source #

Deprecated: renamed to Typeable

type Typeable4 a = Typeable a Source #

Deprecated: renamed to Typeable

type Typeable5 a = Typeable a Source #

Deprecated: renamed to Typeable

type Typeable6 a = Typeable a Source #

Deprecated: renamed to Typeable

type Typeable7 a = Typeable a Source #

Deprecated: renamed to Typeable

Type-safe cast

cast :: forall a b. (Typeable a, Typeable b) => a -> Maybe b Source #

The type-safe cast operation

eqT :: forall a b. (Typeable a, Typeable b) => Maybe (a :~: b) Source #

Extract a witness of equality of two types

Since: 4.7.0.0

gcast :: forall a b c. (Typeable a, Typeable b) => c a -> Maybe (c b) Source #

A flexible variation parameterised in a type constructor

Generalized casts for higher-order kinds

gcast1 :: forall c t t' a. (Typeable t, Typeable t') => c (t a) -> Maybe (c (t' a)) Source #

Cast over k1 -> k2

gcast2 :: forall c t t' a b. (Typeable t, Typeable t') => c (t a b) -> Maybe (c (t' a b)) Source #

Cast over k1 -> k2 -> k3

A canonical proxy type

data Proxy t Source #

A concrete, poly-kinded proxy type

Constructors

Proxy 

Instances

Monad (Proxy *) Source # 

Methods

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

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

return :: a -> Proxy * a Source #

fail :: String -> Proxy * a Source #

Functor (Proxy *) Source # 

Methods

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

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

Applicative (Proxy *) Source # 

Methods

pure :: a -> Proxy * a Source #

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

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

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

Foldable (Proxy *) Source # 

Methods

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

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

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

Traversable (Proxy *) Source # 

Methods

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

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

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

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

Generic1 (Proxy *) Source # 

Associated Types

type Rep1 (Proxy * :: * -> *) :: * -> * Source #

Methods

from1 :: Proxy * a -> Rep1 (Proxy *) a Source #

to1 :: Rep1 (Proxy *) a -> Proxy * a Source #

MonadPlus (Proxy *) Source # 

Methods

mzero :: Proxy * a Source #

mplus :: Proxy * a -> Proxy * a -> Proxy * a Source #

Alternative (Proxy *) Source # 

Methods

empty :: Proxy * a Source #

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

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

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

MonadZip (Proxy *) Source # 

Methods

mzip :: Proxy * a -> Proxy * b -> Proxy * (a, b) Source #

mzipWith :: (a -> b -> c) -> Proxy * a -> Proxy * b -> Proxy * c Source #

munzip :: Proxy * (a, b) -> (Proxy * a, Proxy * b) Source #

Show1 (Proxy *) Source #

Since: 4.9.0.0

Methods

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

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

Read1 (Proxy *) Source #

Since: 4.9.0.0

Methods

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

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

Ord1 (Proxy *) Source #

Since: 4.9.0.0

Methods

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

Eq1 (Proxy *) Source #

Since: 4.9.0.0

Methods

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

Bounded (Proxy k s) Source # 

Methods

minBound :: Proxy k s Source #

maxBound :: Proxy k s Source #

Enum (Proxy k s) Source # 

Methods

succ :: Proxy k s -> Proxy k s Source #

pred :: Proxy k s -> Proxy k s Source #

toEnum :: Int -> Proxy k s Source #

fromEnum :: Proxy k s -> Int Source #

enumFrom :: Proxy k s -> [Proxy k s] Source #

enumFromThen :: Proxy k s -> Proxy k s -> [Proxy k s] Source #

enumFromTo :: Proxy k s -> Proxy k s -> [Proxy k s] Source #

enumFromThenTo :: Proxy k s -> Proxy k s -> Proxy k s -> [Proxy k s] Source #

Eq (Proxy k s) Source # 

Methods

(==) :: Proxy k s -> Proxy k s -> Bool #

(/=) :: Proxy k s -> Proxy k s -> Bool #

Data t => Data (Proxy * t) Source # 

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Proxy * t -> c (Proxy * t) Source #

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Proxy * t) Source #

toConstr :: Proxy * t -> Constr Source #

dataTypeOf :: Proxy * t -> DataType Source #

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

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

gmapT :: (forall b. Data b => b -> b) -> Proxy * t -> Proxy * t Source #

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Proxy * t -> r Source #

gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Proxy * t -> r Source #

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

gmapQi :: Int -> (forall d. Data d => d -> u) -> Proxy * t -> u Source #

gmapM :: Monad m => (forall d. Data d => d -> m d) -> Proxy * t -> m (Proxy * t) Source #

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Proxy * t -> m (Proxy * t) Source #

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Proxy * t -> m (Proxy * t) Source #

Ord (Proxy k s) Source # 

Methods

compare :: Proxy k s -> Proxy k s -> Ordering #

(<) :: Proxy k s -> Proxy k s -> Bool #

(<=) :: Proxy k s -> Proxy k s -> Bool #

(>) :: Proxy k s -> Proxy k s -> Bool #

(>=) :: Proxy k s -> Proxy k s -> Bool #

max :: Proxy k s -> Proxy k s -> Proxy k s #

min :: Proxy k s -> Proxy k s -> Proxy k s #

Read (Proxy k s) Source # 
Show (Proxy k s) Source # 

Methods

showsPrec :: Int -> Proxy k s -> ShowS Source #

show :: Proxy k s -> String Source #

showList :: [Proxy k s] -> ShowS Source #

Ix (Proxy k s) Source # 

Methods

range :: (Proxy k s, Proxy k s) -> [Proxy k s] Source #

index :: (Proxy k s, Proxy k s) -> Proxy k s -> Int Source #

unsafeIndex :: (Proxy k s, Proxy k s) -> Proxy k s -> Int

inRange :: (Proxy k s, Proxy k s) -> Proxy k s -> Bool Source #

rangeSize :: (Proxy k s, Proxy k s) -> Int Source #

unsafeRangeSize :: (Proxy k s, Proxy k s) -> Int

Generic (Proxy k t) Source # 

Associated Types

type Rep (Proxy k t) :: * -> * Source #

Methods

from :: Proxy k t -> Rep (Proxy k t) x Source #

to :: Rep (Proxy k t) x -> Proxy k t Source #

Semigroup (Proxy k s) Source # 

Methods

(<>) :: Proxy k s -> Proxy k s -> Proxy k s Source #

sconcat :: NonEmpty (Proxy k s) -> Proxy k s Source #

stimes :: Integral b => b -> Proxy k s -> Proxy k s Source #

Monoid (Proxy k s) Source # 

Methods

mempty :: Proxy k s Source #

mappend :: Proxy k s -> Proxy k s -> Proxy k s Source #

mconcat :: [Proxy k s] -> Proxy k s Source #

type Rep1 (Proxy *) Source # 
type Rep1 (Proxy *) = D1 (MetaData "Proxy" "Data.Proxy" "base" False) (C1 (MetaCons "Proxy" PrefixI False) U1)
type Rep (Proxy k t) Source # 
type Rep (Proxy k t) = D1 (MetaData "Proxy" "Data.Proxy" "base" False) (C1 (MetaCons "Proxy" PrefixI False) U1)

Type representations

data TypeRep Source #

A concrete representation of a (monomorphic) type. TypeRep supports reasonably efficient equality.

Instances

typeRepFingerprint :: TypeRep -> Fingerprint Source #

Observe the Fingerprint of a type representation

Since: 4.8.0.0

rnfTypeRep :: TypeRep -> () Source #

Helper to fully evaluate TypeRep for use as NFData(rnf) implementation

Since: 4.8.0.0

showsTypeRep :: TypeRep -> ShowS Source #

data TyCon :: * #

Instances

tyConFingerprint :: TyCon -> Fingerprint Source #

tyConString :: TyCon -> String Source #

Deprecated: renamed to tyConName; tyConModule and tyConPackage are also available.

Observe string encoding of a type representation

tyConPackage :: TyCon -> String Source #

tyConModule :: TyCon -> String Source #

tyConName :: TyCon -> String Source #

rnfTyCon :: TyCon -> () Source #

Construction of type representations

mkTyCon3 Source #

Arguments

:: String

package name

-> String

module name

-> String

the name of the type constructor

-> TyCon

A unique TyCon object Used when the strings are dynamically allocated, eg from binary deserialisation

mkTyConApp :: TyCon -> [TypeRep] -> TypeRep Source #

Applies a kind-monomorphic type constructor to a sequence of types

mkAppTy :: TypeRep -> TypeRep -> TypeRep Source #

Adds a TypeRep argument to a TypeRep.

mkFunTy :: TypeRep -> TypeRep -> TypeRep Source #

A special case of mkTyConApp, which applies the function type constructor to a pair of types.

Observation of type representations

splitTyConApp :: TypeRep -> (TyCon, [TypeRep]) Source #

Splits a type constructor application. Note that if the type constructor is polymorphic, this will not return the kinds that were used. See splitPolyTyConApp if you need all parts.

funResultTy :: TypeRep -> TypeRep -> Maybe TypeRep Source #

Applies a type to a function type. Returns: Just u if the first argument represents a function of type t -> u and the second argument represents a function of type t. Otherwise, returns Nothing.

typeRepTyCon :: TypeRep -> TyCon Source #

Observe the type constructor of a type representation

typeRepArgs :: TypeRep -> [TypeRep] Source #

Observe the argument types of a type representation