Data.Void

base-4.9.0.0: Basic libraries

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: 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: 4.8.0.0

Instances

Eq Void |
Methods (==) :: Void -> Void -> Bool Source (/=) :: Void -> Void -> Bool Source
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 (TYPE Lifted -> TYPE Lifted) t => (forall d. Data d => c (t d)) -> Maybe (c Void) Source dataCast2 :: Typeable (TYPE Lifted -> TYPE Lifted -> TYPE Lifted) 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 :: (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 |
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
Read Void | Reading a `Void` value is always a parse error, considering `Void` as a data type with no constructors.
Methods readsPrec :: Int -> ReadS Void Source readList :: ReadS [Void] Source readPrec :: ReadPrec Void Source readListPrec :: ReadPrec [Void] Source
Show Void |
Methods showsPrec :: Int -> Void -> ShowS Source show :: Void -> String Source showList :: [Void] -> ShowS Source
Ix Void |
Methods range :: (Void, Void) -> [Void] Source index :: (Void, Void) -> Void -> Int Source unsafeIndex :: (Void, Void) -> Void -> Int inRange :: (Void, Void) -> Void -> Bool Source rangeSize :: (Void, Void) -> Int Source unsafeRangeSize :: (Void, Void) -> Int
Generic Void |
Associated Types type Rep Void :: * -> * Source Methods from :: Void -> Rep Void x Source to :: Rep Void x -> Void Source
Semigroup Void |
Methods (<>) :: Void -> Void -> Void Source sconcat :: NonEmpty Void -> Void Source stimes :: Integral b => b -> Void -> Void Source
Exception Void |
Methods toException :: Void -> SomeException Source fromException :: SomeException -> Maybe Void Source displayException :: Void -> String Source
type Rep Void = D1 (MetaData "Void" "Data.Void" "base" False) V1 |

absurd :: Void -> a Source

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

Since: 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.

Since: 4.8.0.0