Selector

Contents

Description

From "Effective Haskell" by Rebecca Skinner (B9.0 14 March 2023).

Synopsis

class Select (f :: Type -> Type) where
- empty :: f a
- select :: f a -> f a -> f a
newtype Selector (f :: Type -> Type) (a :: Type) = Selector (f a)
newtype MyMaybe a = MyMaybe (Maybe a)

Types

class Select (f :: Type -> Type) where Source #

A class for types that can be used to select between two values.

Methods

select :: f a -> f a -> f a Source #

Instances details

Select Maybe Source #	Instances of `Select` for `Maybe`.
Instance details Defined in Selector Methods empty :: Maybe a Source # select :: Maybe a -> Maybe a -> Maybe a Source #
Select [] Source #	Instances of `Select` for lists '[]'.
Instance details Defined in Selector Methods empty :: [a] Source # select :: [a] -> [a] -> [a] Source #

newtype Selector (f :: Type -> Type) (a :: Type) Source #

Constructors

Instances details

Select f => Monoid (Selector f a) Source #	Monoid instance for `Selector`.
Instance details Defined in Selector Methods mempty :: Selector f a # mappend :: Selector f a -> Selector f a -> Selector f a # mconcat :: [Selector f a] -> Selector f a #
Select f => Semigroup (Selector f a) Source #	Semigroup instance for `Selector`.
Instance details Defined in Selector Methods (<>) :: Selector f a -> Selector f a -> Selector f a # sconcat :: NonEmpty (Selector f a) -> Selector f a # stimes :: Integral b => b -> Selector f a -> Selector f a #
Show (f a) => Show (Selector f a) Source #
Instance details Defined in Selector Methods showsPrec :: Int -> Selector f a -> ShowS # show :: Selector f a -> String # showList :: [Selector f a] -> ShowS #
Eq (f a) => Eq (Selector f a) Source #
Instance details Defined in Selector Methods (==) :: Selector f a -> Selector f a -> Bool # (/=) :: Selector f a -> Selector f a -> Bool #

MyMaybe and 'Selector Maybe a' are representationally equal to 'Maybe a'.

Constructors

Instances details

Monoid (MyMaybe a) Source #
Instance details Defined in Selector Methods mempty :: MyMaybe a # mappend :: MyMaybe a -> MyMaybe a -> MyMaybe a # mconcat :: [MyMaybe a] -> MyMaybe a #
Semigroup (MyMaybe a) Source #
Instance details Defined in Selector Methods (<>) :: MyMaybe a -> MyMaybe a -> MyMaybe a # sconcat :: NonEmpty (MyMaybe a) -> MyMaybe a # stimes :: Integral b => b -> MyMaybe a -> MyMaybe a #
Show a => Show (MyMaybe a) Source #
Instance details Defined in Selector Methods showsPrec :: Int -> MyMaybe a -> ShowS # show :: MyMaybe a -> String # showList :: [MyMaybe a] -> ShowS #
Eq a => Eq (MyMaybe a) Source #
Instance details Defined in Selector Methods (==) :: MyMaybe a -> MyMaybe a -> Bool # (/=) :: MyMaybe a -> MyMaybe a -> Bool #