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/Haskell 8

Data.Bool

Copyright (c) The University of Glasgow 2001
License BSD-style (see the file libraries/base/LICENSE)
Maintainer [email protected]
Stability experimental
Portability portable
Safe Haskell Trustworthy
Language Haskell2010

Description

The Bool type and related functions.

Booleans

data Bool :: * Source

Constructors

False
True

Instances

Bounded Bool

Since: 2.1
Enum Bool

Since: 2.1
Eq Bool

Methods

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

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

Data Bool

Since: 4.0.0.0

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 :: (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

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: 2.1
Show Bool
Ix Bool

Since: 2.1

Methods

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

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

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

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

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

unsafeRangeSize :: (Bool, Bool) -> Int

Generic Bool

Associated Types

type Rep Bool :: * -> * Source

Methods

from :: Bool -> Rep Bool x Source

to :: Rep Bool x -> Bool Source

FiniteBits Bool

Since: 4.7.0.0
Bits Bool

Interpret Bool as 1-bit bit-field

Since: 4.7.0.0
Storable Bool

Since: 2.1
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 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

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

© The University of Glasgow and others
Licensed under a BSD-style license (see top of the page).
https://downloads.haskell.org/~ghc/8.2.1/docs/html/libraries/base-4.10.0.0/Data-Bool.html