Safe Haskell	None
Language	Haskell2010

Data.Monoid.RightAction

Synopsis

class RightAction m s where
- actRight :: s -> m -> s
type REndo s = Dual (Endo s)
rEndo :: (s -> s) -> REndo s

Documentation

class RightAction m s where Source #

A right action of m on s.

Imagine s to be a type of states, and m a type of changes to s.

Laws:

When m is a Semigroup: s `actRight` m1 `actRight` m2 == s `actRight` (m1 <> m2)
When m is a Monoid: s `actRight` mempty == s

The default implementation is the trivial action which leaves s unchanged.

See also Action from monoid-extras, which is a left action.

Minimal complete definition

Nothing

Methods

actRight :: s -> m -> s infixl 5 Source #

Instances

Instances details

RightAction Void s Source #
Instance details Defined in Data.Monoid.RightAction Methods actRight :: s -> Void -> s Source #
RightAction Count Int Source #
Instance details Defined in Control.Monad.Trans.Changeset Methods actRight :: Int -> Count -> Int Source #
RightAction () s Source #
Instance details Defined in Data.Monoid.RightAction Methods actRight :: s -> () -> s Source #
RightAction m () Source #
Instance details Defined in Data.Monoid.RightAction Methods actRight :: () -> m -> () Source #
Semigroup m => RightAction m (Regular m) Source #
Instance details Defined in Data.Monoid.RightAction Methods actRight :: Regular m -> m -> Regular m Source #
RightAction (Last s) s Source #
Instance details Defined in Data.Monoid.RightAction Methods actRight :: s -> Last s -> s Source #
Action m s => RightAction (Dual m) s Source #
Instance details Defined in Data.Monoid.RightAction Methods actRight :: s -> Dual m -> s Source #
RightAction w s => RightAction (Changes w) s Source #	Apply all changes sequentially
Instance details Defined in Control.Monad.Trans.Changeset Methods actRight :: s -> Changes w -> s Source #
RightAction m s => RightAction (Maybe m) s Source #
Instance details Defined in Data.Monoid.RightAction Methods actRight :: s -> Maybe m -> s Source #
RightAction (ListChange a) [a] Source #
Instance details Defined in Control.Monad.Trans.Changeset Methods actRight :: [a] -> ListChange a -> [a] Source #
RightAction (MaybeChange a) (Maybe a) Source #
Instance details Defined in Control.Monad.Trans.Changeset Methods actRight :: Maybe a -> MaybeChange a -> Maybe a Source #
(RightAction m s, RightAction n s) => RightAction (m :+: n) s Source #
Instance details Defined in Data.Monoid.RightAction.Coproduct Methods actRight :: s -> (m :+: n) -> s Source #
(Functor f, RightAction w s) => RightAction (FmapChange f w) (f s) Source #
Instance details Defined in Control.Monad.Trans.Changeset Methods actRight :: f s -> FmapChange f w -> f s Source #

type REndo s = Dual (Endo s) Source #

Endomorphism type with reverse Monoid instance.

The standard Endo type has a left action on s since its composition is defined as Endo f <> Endo g = Endo (f . g). The "Right Endomorphism" type, on the other hand, has a right action. Intuitively, it behaves like the & operator:

s & f & g == s `actRight` rEndo f <> rEndo g

rEndo :: (s -> s) -> REndo s Source #

Create an endomorphism monoid that has a right action on s.