Data.Monoid.Instances.Stateful

This module defines the monoid transformer data type Stateful.

> let s = setState [4] $ pure "data" :: Stateful [Int] String
> s
Stateful ("data",[4])
> factors s
[Stateful ("d",[]),Stateful ("a",[]),Stateful ("t",[]),Stateful ("a",[]),Stateful ("",[4])]

Documentation

newtype Stateful a b

Stateful a b is a wrapper around the Monoid b that carries the state a along. The state type a must be a monoid as well if Stateful is to be of any use. In the FactorialMonoid and TextualMonoid class instances, the monoid b has the priority and the state a is left for the end.

Constructors

Stateful (b, a)

Instances

Functor (Stateful a)

Monoid a => Applicative (Stateful a)

(Eq a, Eq b) => Eq (Stateful a b)

(Ord a, Ord b) => Ord (Stateful a b)

(Show a, Show b) => Show (Stateful a b)

(Monoid a, IsString b) => IsString (Stateful a b)

(Monoid a, Monoid b) => Monoid (Stateful a b)

(PositiveMonoid a, PositiveMonoid b) => PositiveMonoid (Stateful a b)

(MonoidNull a, MonoidNull b) => MonoidNull (Stateful a b)

(StableFactorialMonoid a, StableFactorialMonoid b) => StableFactorialMonoid (Stateful a b)

(FactorialMonoid a, FactorialMonoid b) => FactorialMonoid (Stateful a b)

(RightGCDMonoid a, RightGCDMonoid b) => RightGCDMonoid (Stateful a b)

(LeftGCDMonoid a, LeftGCDMonoid b) => LeftGCDMonoid (Stateful a b)

(RightReductiveMonoid a, RightReductiveMonoid b) => RightReductiveMonoid (Stateful a b)

(LeftReductiveMonoid a, LeftReductiveMonoid b) => LeftReductiveMonoid (Stateful a b)

(LeftGCDMonoid a, FactorialMonoid a, TextualMonoid b) => TextualMonoid (Stateful a b)

extract :: Stateful a b -> b

state :: Stateful a b -> a

setState :: a -> Stateful a b -> Stateful a b