Copyright	(C) 2008-2014 Edward Kmett
License	BSD-style (see the file libraries/base/LICENSE)
Maintainer	Edward Kmett <ekmett@gmail.com>
Stability	provisional
Portability	portable
Safe Haskell	Safe
Language	Haskell2010

Data.Void

Description

A logically uninhabited data type, used to indicate that a given term should not exist.

Since: base-4.8.0.0

Synopsis

data Void
absurd :: Void -> a
vacuous :: Functor f => f Void -> f a

Documentation

data Void Source #

Uninhabited data type

@since base-4.8.0.0

Instances

Instances details

Semigroup Void

@since base-4.9.0.0

Instance details

Defined in GHC.Internal.Base

Methods

(<>) :: Void -> Void -> Void Source #

sconcat :: NonEmpty Void -> Void Source #

stimes :: Integral b => b -> Void -> Void Source #

Data Void

@since base-4.8.0.0

Instance details

Defined in GHC.Internal.Data.Data

Methods

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

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

toConstr :: Void -> Constr Source #

dataTypeOf :: Void -> DataType Source #

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

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

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

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

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

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

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

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

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

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

Exception Void

@since base-4.8.0.0

Instance details

Defined in GHC.Internal.Exception.Type

Methods

toException :: Void -> SomeException Source #

fromException :: SomeException -> Maybe Void Source #

displayException :: Void -> String Source #

backtraceDesired :: Void -> Bool Source #

Generic Void

Instance details

Defined in GHC.Internal.Generics

Associated Types

type Rep Void	@since base-4.8.0.0
Instance details Defined in GHC.Internal.Generics type Rep Void = D1 ('MetaData "Void" "GHC.Internal.Base" "ghc-internal" 'False) (V1 :: Type -> Type)

Methods

from :: Void -> Rep Void x Source #

to :: Rep Void x -> Void Source #

Ix Void

@since base-4.8.0.0

Instance details

Defined in GHC.Internal.Ix

Methods

range :: (Void, Void) -> [Void] Source #

index :: (Void, Void) -> Void -> Int Source #

unsafeIndex :: (Void, Void) -> Void -> Int Source #

inRange :: (Void, Void) -> Void -> Bool Source #

rangeSize :: (Void, Void) -> Int Source #

unsafeRangeSize :: (Void, Void) -> Int Source #

Read Void

Reading a Void value is always a parse error, considering Void as a data type with no constructors.

@since base-4.8.0.0

Instance details

Defined in GHC.Internal.Read

Methods

readsPrec :: Int -> ReadS Void Source #

readList :: ReadS [Void] Source #

readPrec :: ReadPrec Void Source #

readListPrec :: ReadPrec [Void] Source #

Show Void

@since base-4.8.0.0

Instance details

Defined in GHC.Internal.Show

Methods

showsPrec :: Int -> Void -> ShowS Source #

show :: Void -> String Source #

showList :: [Void] -> ShowS Source #

Eq Void

@since base-4.8.0.0

Instance details

Defined in GHC.Internal.Base

Methods

(==) :: Void -> Void -> Bool Source #

(/=) :: Void -> Void -> Bool Source #

Ord Void

@since base-4.8.0.0

Instance details

Defined in GHC.Internal.Base

Methods

compare :: Void -> Void -> Ordering Source #

(<) :: Void -> Void -> Bool Source #

(<=) :: Void -> Void -> Bool Source #

(>) :: Void -> Void -> Bool Source #

(>=) :: Void -> Void -> Bool Source #

max :: Void -> Void -> Void Source #

min :: Void -> Void -> Void Source #

type Rep Void

@since base-4.8.0.0

Instance details

Defined in GHC.Internal.Generics

type Rep Void = D1 ('MetaData "Void" "GHC.Internal.Base" "ghc-internal" 'False) (V1 :: Type -> Type)

absurd :: Void -> a Source #

Since Void values logically don't exist, this witnesses the logical reasoning tool of "ex falso quodlibet".

>>> let x :: Either Void Int; x = Right 5
>>> :{
case x of
    Right r -> r
    Left l  -> absurd l
:}
5

@since base-4.8.0.0

vacuous :: Functor f => f Void -> f a Source #

If Void is uninhabited then any Functor that holds only values of type Void is holding no values. It is implemented in terms of fmap absurd.

@since base-4.8.0.0