Copyright	(c) The University of Glasgow 2001
License	BSD-style (see the file libraries/base/LICENSE)
Maintainer	libraries@haskell.org
Stability	experimental
Portability	portable
Safe Haskell	Trustworthy
Language	Haskell2010

Data.Bool

Contents

Booleans
- Operations

Description

The Bool type and related functions.

Synopsis

data Bool
- = False
- | True
(&&) :: Bool -> Bool -> Bool
(||) :: Bool -> Bool -> Bool
not :: Bool -> Bool
otherwise :: Bool
bool :: a -> a -> Bool -> a

Booleans

data Bool Source #

Constructors

False
True

Instances

Instances details

Bounded Bool #	Since: base-2.1
Instance details Defined in GHC.Enum Methods minBound :: Bool Source # maxBound :: Bool Source #
Enum Bool #	Since: base-2.1
Instance details Defined in GHC.Enum Methods succ :: Bool -> Bool Source # pred :: Bool -> Bool Source # toEnum :: Int -> Bool Source # fromEnum :: Bool -> Int Source # enumFrom :: Bool -> [Bool] Source # enumFromThen :: Bool -> Bool -> [Bool] Source # enumFromTo :: Bool -> Bool -> [Bool] Source # enumFromThenTo :: Bool -> Bool -> Bool -> [Bool] Source #
Eq Bool
Instance details Defined in GHC.Classes Methods (==) :: Bool -> Bool -> Bool Source # (/=) :: Bool -> Bool -> Bool Source #
Data Bool #	Since: base-4.0.0.0
Instance details Defined in Data.Data Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Bool -> c Bool Source # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c Bool Source # toConstr :: Bool -> Constr Source # dataTypeOf :: Bool -> DataType Source # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c Bool) Source # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c Bool) Source # gmapT :: (forall b. Data b => b -> b) -> Bool -> Bool Source # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Bool -> r Source # gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Bool -> r Source # gmapQ :: (forall d. Data d => d -> u) -> Bool -> [u] Source # gmapQi :: Int -> (forall d. Data d => d -> u) -> Bool -> u Source # gmapM :: Monad m => (forall d. Data d => d -> m d) -> Bool -> m Bool Source # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Bool -> m Bool Source # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Bool -> m Bool Source #
Ord Bool
Instance details Defined in GHC.Classes Methods compare :: Bool -> Bool -> Ordering Source # (<) :: Bool -> Bool -> Bool Source # (<=) :: Bool -> Bool -> Bool Source # (>) :: Bool -> Bool -> Bool Source # (>=) :: Bool -> Bool -> Bool Source # max :: Bool -> Bool -> Bool Source # min :: Bool -> Bool -> Bool Source #
Read Bool #	Since: base-2.1
Instance details Defined in GHC.Read Methods readsPrec :: Int -> ReadS Bool Source # readList :: ReadS [Bool] Source # readPrec :: ReadPrec Bool Source # readListPrec :: ReadPrec [Bool] Source #
Show Bool #	Since: base-2.1
Instance details Defined in GHC.Show Methods showsPrec :: Int -> Bool -> ShowS Source # show :: Bool -> String Source # showList :: [Bool] -> ShowS Source #
Ix Bool #	Since: base-2.1
Instance details Defined in GHC.Ix Methods range :: (Bool, Bool) -> [Bool] Source # index :: (Bool, Bool) -> Bool -> Int Source # unsafeIndex :: (Bool, Bool) -> Bool -> Int Source # inRange :: (Bool, Bool) -> Bool -> Bool Source # rangeSize :: (Bool, Bool) -> Int Source # unsafeRangeSize :: (Bool, Bool) -> Int Source #
Generic Bool #	Since: base-4.6.0.0
Instance details Defined in GHC.Generics Associated Types type Rep Bool :: Type -> Type Source # Methods from :: Bool -> Rep Bool x Source # to :: Rep Bool x -> Bool Source #
FiniteBits Bool #	Since: base-4.7.0.0
Instance details Defined in Data.Bits Methods finiteBitSize :: Bool -> Int Source # countLeadingZeros :: Bool -> Int Source # countTrailingZeros :: Bool -> Int Source #
Bits Bool #	Interpret `Bool` as 1-bit bit-field Since: base-4.7.0.0
Instance details Defined in Data.Bits Methods (.&.) :: Bool -> Bool -> Bool Source # (.\|.) :: Bool -> Bool -> Bool Source # xor :: Bool -> Bool -> Bool Source # complement :: Bool -> Bool Source # shift :: Bool -> Int -> Bool Source # rotate :: Bool -> Int -> Bool Source # zeroBits :: Bool Source # bit :: Int -> Bool Source # setBit :: Bool -> Int -> Bool Source # clearBit :: Bool -> Int -> Bool Source # complementBit :: Bool -> Int -> Bool Source # testBit :: Bool -> Int -> Bool Source # bitSizeMaybe :: Bool -> Maybe Int Source # bitSize :: Bool -> Int Source # isSigned :: Bool -> Bool Source # shiftL :: Bool -> Int -> Bool Source # unsafeShiftL :: Bool -> Int -> Bool Source # shiftR :: Bool -> Int -> Bool Source # unsafeShiftR :: Bool -> Int -> Bool Source # rotateL :: Bool -> Int -> Bool Source # rotateR :: Bool -> Int -> Bool Source # popCount :: Bool -> Int Source #
Storable Bool #	Since: base-2.1
Instance details Defined in Foreign.Storable Methods sizeOf :: Bool -> Int Source # alignment :: Bool -> Int Source # peekElemOff :: Ptr Bool -> Int -> IO Bool Source # pokeElemOff :: Ptr Bool -> Int -> Bool -> IO () Source # peekByteOff :: Ptr b -> Int -> IO Bool Source # pokeByteOff :: Ptr b -> Int -> Bool -> IO () Source # peek :: Ptr Bool -> IO Bool Source # poke :: Ptr Bool -> Bool -> IO () Source #
type Rep Bool #
Instance details Defined in GHC.Generics type Rep Bool = D1 ('MetaData "Bool" "GHC.Types" "ghc-prim" 'False) (C1 ('MetaCons "False" 'PrefixI 'False) (U1 :: Type -> Type) :+: C1 ('MetaCons "True" 'PrefixI 'False) (U1 :: Type -> Type))

Operations

(&&) :: Bool -> Bool -> Bool infixr 3 Source #

Boolean "and", lazy in the second argument

(||) :: Bool -> Bool -> Bool infixr 2 Source #

Boolean "or", lazy in the second argument

not :: Bool -> Bool Source #

Boolean "not"

otherwise :: Bool Source #

otherwise is defined as the value True. It helps to make guards more readable. eg.

 f x | x < 0     = ...
     | otherwise = ...

bool :: a -> a -> Bool -> a Source #

Case analysis for the Bool type. bool x y p evaluates to x when p is False, and evaluates to y when p is True.

This is equivalent to if p then y else x; that is, one can think of it as an if-then-else construct with its arguments reordered.

Examples

Expand

Basic usage:

>>> bool "foo" "bar" True
"bar"
>>> bool "foo" "bar" False
"foo"

Confirm that bool x y p and if p then y else x are equivalent:

>>> let p = True; x = "bar"; y = "foo"
>>> bool x y p == if p then y else x
True
>>> let p = False
>>> bool x y p == if p then y else x
True

Since: base-4.7.0.0