relude-0.4.0: Custom prelude from Kowainik

Copyright(c) 2016 Stephen Diehl
(c) 20016-2018 Serokell
(c) 2018 Kowainik
LicenseMIT
MaintainerKowainik <xrom.xkov@gmail.com>
Safe HaskellSafe
LanguageHaskell2010

Relude.Bool.Reexport

Description

Reexports functions to work with Bool type.

Synopsis

Documentation

guard :: Alternative f => Bool -> f () #

Conditional failure of Alternative computations. Defined by

guard True  = pure ()
guard False = empty

Examples

Expand

Common uses of guard include conditionally signaling an error in an error monad and conditionally rejecting the current choice in an Alternative-based parser.

As an example of signaling an error in the error monad Maybe, consider a safe division function safeDiv x y that returns Nothing when the denominator y is zero and Just (x `div` y) otherwise. For example:

>>> safeDiv 4 0
Nothing
>>> safeDiv 4 2
Just 2

A definition of safeDiv using guards, but not guard:

safeDiv :: Int -> Int -> Maybe Int
safeDiv x y | y /= 0    = Just (x `div` y)
            | otherwise = Nothing

A definition of safeDiv using guard and Monad do-notation:

safeDiv :: Int -> Int -> Maybe Int
safeDiv x y = do
  guard (y /= 0)
  return (x `div` y)

unless :: Applicative f => Bool -> f () -> f () #

The reverse of when.

when :: Applicative f => Bool -> f () -> f () #

Conditional execution of Applicative expressions. For example,

when debug (putStrLn "Debugging")

will output the string Debugging if the Boolean value debug is True, and otherwise do nothing.

otherwise :: Bool #

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

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

data Bool #

Constructors

False 
True 
Instances
Bounded Bool

Since: base-2.1

Instance details

Defined in GHC.Enum

Enum Bool

Since: base-2.1

Instance details

Defined in GHC.Enum

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 
Instance details

Defined in GHC.Classes

Methods

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

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

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 #

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 
Instance details

Defined in GHC.Classes

Methods

compare :: Bool -> Bool -> Ordering #

(<) :: Bool -> Bool -> Bool #

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

(>) :: Bool -> Bool -> Bool #

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

max :: Bool -> Bool -> Bool #

min :: Bool -> Bool -> Bool #

Read Bool

Since: base-2.1

Instance details

Defined in GHC.Read

Show Bool

Since: base-2.1

Instance details

Defined in GHC.Show

Methods

showsPrec :: Int -> Bool -> ShowS #

show :: Bool -> String #

showList :: [Bool] -> ShowS #

Ix Bool

Since: base-2.1

Instance details

Defined in GHC.Arr

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 
Instance details

Defined in GHC.Generics

Associated Types

type Rep Bool :: Type -> Type #

Methods

from :: Bool -> Rep Bool x #

to :: Rep Bool x -> Bool #

SingKind Bool

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Associated Types

type DemoteRep Bool :: Type

Methods

fromSing :: Sing a -> DemoteRep Bool

Bits Bool

Interpret Bool as 1-bit bit-field

Since: base-4.7.0.0

Instance details

Defined in Data.Bits

FiniteBits Bool

Since: base-4.7.0.0

Instance details

Defined in Data.Bits

NFData Bool 
Instance details

Defined in Control.DeepSeq

Methods

rnf :: Bool -> () #

Hashable Bool 
Instance details

Defined in Data.Hashable.Class

Methods

hashWithSalt :: Int -> Bool -> Int #

hash :: Bool -> Int #

SingI False

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

sing :: Sing False

SingI True

Since: base-4.9.0.0

Instance details

Defined in GHC.Generics

Methods

sing :: Sing True

type Rep Bool

Since: base-4.6.0.0

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))
data Sing (a :: Bool) 
Instance details

Defined in GHC.Generics

data Sing (a :: Bool) where
type DemoteRep Bool 
Instance details

Defined in GHC.Generics

type DemoteRep Bool = Bool

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

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

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

Boolean "and"

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

Boolean "or"

not :: Bool -> Bool #

Boolean "not"