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Data.Type.Coercion

License	BSD-style (see the LICENSE file in the distribution)
Maintainer	[email protected]
Stability	experimental
Portability	not portable
Safe Haskell	None
Language	Haskell2010

Description

Definition of representational equality (Coercion).

Since: base-4.7.0.0

data Coercion a b where Source

Representational equality. If Coercion a b is inhabited by some terminating value, then the type a has the same underlying representation as the type b.

To use this equality in practice, pattern-match on the Coercion a b to get out the Coercible a b instance, and then use coerce to apply it.

Since: base-4.7.0.0

Constructors

Coercion :: Coercible a b => Coercion a b

Instances

Instances details

Category (Coercion :: k -> k -> Type)	Since: base-4.7.0.0
Instance details Defined in Control.Category Methods id :: forall (a :: k0). Coercion a a Source (.) :: forall (b :: k0) (c :: k0) (a :: k0). Coercion b c -> Coercion a b -> Coercion a c Source
TestCoercion (Coercion a :: k -> Type)	Since: base-4.7.0.0
Instance details Defined in Data.Type.Coercion Methods testCoercion :: forall (a0 :: k0) (b :: k0). Coercion a a0 -> Coercion a b -> Maybe (Coercion a0 b) Source
Coercible a b => Bounded (Coercion a b)	Since: base-4.7.0.0
Instance details Defined in Data.Type.Coercion Methods minBound :: Coercion a b Source maxBound :: Coercion a b Source
Coercible a b => Enum (Coercion a b)	Since: base-4.7.0.0
Instance details Defined in Data.Type.Coercion Methods succ :: Coercion a b -> Coercion a b Source pred :: Coercion a b -> Coercion a b Source toEnum :: Int -> Coercion a b Source fromEnum :: Coercion a b -> Int Source enumFrom :: Coercion a b -> [Coercion a b] Source enumFromThen :: Coercion a b -> Coercion a b -> [Coercion a b] Source enumFromTo :: Coercion a b -> Coercion a b -> [Coercion a b] Source enumFromThenTo :: Coercion a b -> Coercion a b -> Coercion a b -> [Coercion a b] Source
Eq (Coercion a b)	Since: base-4.7.0.0
Instance details Defined in Data.Type.Coercion Methods (==) :: Coercion a b -> Coercion a b -> Bool Source (/=) :: Coercion a b -> Coercion a b -> Bool Source
(Coercible a b, Data a, Data b) => Data (Coercion a b)	Since: base-4.7.0.0
Instance details Defined in Data.Data Methods gfoldl :: (forall d b0. Data d => c (d -> b0) -> d -> c b0) -> (forall g. g -> c g) -> Coercion a b -> c (Coercion a b) Source gunfold :: (forall b0 r. Data b0 => c (b0 -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Coercion a b) Source toConstr :: Coercion a b -> Constr Source dataTypeOf :: Coercion a b -> DataType Source dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Coercion a b)) Source dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Coercion a b)) Source gmapT :: (forall b0. Data b0 => b0 -> b0) -> Coercion a b -> Coercion a b Source gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Coercion a b -> r Source gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Coercion a b -> r Source gmapQ :: (forall d. Data d => d -> u) -> Coercion a b -> [u] Source gmapQi :: Int -> (forall d. Data d => d -> u) -> Coercion a b -> u Source gmapM :: Monad m => (forall d. Data d => d -> m d) -> Coercion a b -> m (Coercion a b) Source gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Coercion a b -> m (Coercion a b) Source gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Coercion a b -> m (Coercion a b) Source
Ord (Coercion a b)	Since: base-4.7.0.0
Instance details Defined in Data.Type.Coercion Methods compare :: Coercion a b -> Coercion a b -> Ordering Source (<) :: Coercion a b -> Coercion a b -> Bool Source (<=) :: Coercion a b -> Coercion a b -> Bool Source (>) :: Coercion a b -> Coercion a b -> Bool Source (>=) :: Coercion a b -> Coercion a b -> Bool Source max :: Coercion a b -> Coercion a b -> Coercion a b Source min :: Coercion a b -> Coercion a b -> Coercion a b Source
Coercible a b => Read (Coercion a b)	Since: base-4.7.0.0
Instance details Defined in Data.Type.Coercion Methods readsPrec :: Int -> ReadS (Coercion a b) Source readList :: ReadS [Coercion a b] Source readPrec :: ReadPrec (Coercion a b) Source readListPrec :: ReadPrec [Coercion a b] Source
Show (Coercion a b)	Since: base-4.7.0.0
Instance details Defined in Data.Type.Coercion Methods showsPrec :: Int -> Coercion a b -> ShowS Source show :: Coercion a b -> String Source showList :: [Coercion a b] -> ShowS Source

coerceWith :: Coercion a b -> a -> b Source

Type-safe cast, using representational equality

gcoerceWith :: Coercion a b -> (Coercible a b => r) -> r Source

Generalized form of type-safe cast using representational equality

Since: base-4.10.0.0

sym :: Coercion a b -> Coercion b a Source

Symmetry of representational equality

trans :: Coercion a b -> Coercion b c -> Coercion a c Source

Transitivity of representational equality

repr :: (a :~: b) -> Coercion a b Source

Convert propositional (nominal) equality to representational equality

class TestCoercion f where Source

This class contains types where you can learn the equality of two types from information contained in terms. Typically, only singleton types should inhabit this class.

Methods

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

Conditionally prove the representational equality of a and b.

Instances

Instances details

TestCoercion (Coercion a :: k -> Type)	Since: base-4.7.0.0
Instance details Defined in Data.Type.Coercion Methods testCoercion :: forall (a0 :: k0) (b :: k0). Coercion a a0 -> Coercion a b -> Maybe (Coercion a0 b) Source
TestCoercion ((:~:) a :: k -> Type)	Since: base-4.7.0.0
Instance details Defined in Data.Type.Coercion Methods testCoercion :: forall (a0 :: k0) (b :: k0). (a :~: a0) -> (a :~: b) -> Maybe (Coercion a0 b) Source
TestCoercion ((:~~:) a :: k -> Type)	Since: base-4.10.0.0
Instance details Defined in Data.Type.Coercion Methods testCoercion :: forall (a0 :: k0) (b :: k0). (a :~~: a0) -> (a :~~: b) -> Maybe (Coercion a0 b) Source

© The University of Glasgow and others
Licensed under a BSD-style license (see top of the page).
https://downloads.haskell.org/~ghc/8.8.3/docs/html/libraries/base-4.13.0.0/Data-Type-Coercion.html