base-4.9.1.0: Basic libraries

Copyright(c) The University of Glasgow 2001
LicenseBSD-style (see the file libraries/base/LICENSE)
Maintainerlibraries@haskell.org
Stabilityexperimental
Portabilityportable
Safe HaskellTrustworthy
LanguageHaskell2010

Data.Bool

Contents

Description

The Bool type and related functions.

Synopsis

Booleans

data Bool :: * Source #

Constructors

False 
True 

Instances

Bounded Bool # 
Enum Bool # 

Methods

succ :: Bool -> Bool #

pred :: Bool -> Bool #

toEnum :: Int -> Bool #

fromEnum :: Bool -> Int #

enumFrom :: Bool -> [Bool] #

enumFromThen :: Bool -> Bool -> [Bool] #

enumFromTo :: Bool -> Bool -> [Bool] #

enumFromThenTo :: Bool -> Bool -> Bool -> [Bool] #

Eq Bool 

Methods

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

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

Data Bool # 

Methods

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

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

toConstr :: Bool -> Constr #

dataTypeOf :: Bool -> DataType #

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

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

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

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

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

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

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

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

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

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

Ord Bool 
Read Bool # 
Show Bool # 

Methods

showsPrec :: Int -> Bool -> ShowS #

show :: Bool -> String #

showList :: [Bool] -> ShowS #

Ix Bool # 

Methods

range :: (Bool, Bool) -> [Bool] #

index :: (Bool, Bool) -> Bool -> Int #

unsafeIndex :: (Bool, Bool) -> Bool -> Int

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

rangeSize :: (Bool, Bool) -> Int #

unsafeRangeSize :: (Bool, Bool) -> Int

Generic Bool # 

Associated Types

type Rep Bool :: * -> * #

Methods

from :: Bool -> Rep Bool x #

to :: Rep Bool x -> Bool #

FiniteBits Bool # 
Bits Bool # 
Storable Bool # 

Methods

sizeOf :: Bool -> Int #

alignment :: Bool -> Int #

peekElemOff :: Ptr Bool -> Int -> IO Bool #

pokeElemOff :: Ptr Bool -> Int -> Bool -> IO () #

peekByteOff :: Ptr b -> Int -> IO Bool #

pokeByteOff :: Ptr b -> Int -> Bool -> IO () #

peek :: Ptr Bool -> IO Bool #

poke :: Ptr Bool -> Bool -> IO () #

type Rep Bool 
type Rep Bool = D1 (MetaData "Bool" "GHC.Types" "ghc-prim" False) ((:+:) (C1 (MetaCons "False" PrefixI False) U1) (C1 (MetaCons "True" PrefixI False) U1))
type (==) Bool a b # 
type (==) Bool a b

Operations

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

Boolean "and"

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

Boolean "or"

not :: Bool -> Bool Source #

Boolean "not"

otherwise :: Bool #

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 #

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

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: 4.7.0.0