base-4.16.0.0: Basic libraries
Copyright(C) 2008-2014 Edward Kmett
LicenseBSD-style (see the file libraries/base/LICENSE)
MaintainerEdward Kmett <ekmett@gmail.com>
Stabilityprovisional
Portabilityportable
Safe HaskellSafe
LanguageHaskell2010

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

Documentation

data Void Source #

Uninhabited data type

Since: base-4.8.0.0

Instances

Instances details
Eq Void #

Since: base-4.8.0.0

Instance details

Defined in Data.Void

Methods

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

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

Data Void #

Since: base-4.8.0.0

Instance details

Defined in Data.Void

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 #

Ord Void #

Since: base-4.8.0.0

Instance details

Defined in Data.Void

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 Data.Void

Show Void #

Since: base-4.8.0.0

Instance details

Defined in Data.Void

Ix Void #

Since: base-4.8.0.0

Instance details

Defined in Data.Void

Generic Void # 
Instance details

Defined in Data.Void

Associated Types

type Rep Void :: Type -> Type Source #

Methods

from :: Void -> Rep Void x Source #

to :: Rep Void x -> Void Source #

Semigroup Void #

Since: base-4.9.0.0

Instance details

Defined in Data.Void

Exception Void #

Since: base-4.8.0.0

Instance details

Defined in Data.Void

type Rep Void #

Since: base-4.8.0.0

Instance details

Defined in Data.Void

type Rep Void = D1 ('MetaData "Void" "Data.Void" "base" '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