StateF.md

Module Halogen.Query.StateF

A part of the HalogenF algebra that replicates a MonadState-like interface.

StateF

data StateF s a
  = Get (s -> a)
  | Modify (s -> s) a

The state algebra.

Instances

instance functorStateF :: Functor (StateF s)

mapState

mapState :: forall s t a. (t -> s) -> ((s -> s) -> t -> t) -> StateF s a -> StateF t a

Map over the state value using a function to extract the new state value from the old state, and a function for modifying the state.

stateN

stateN :: forall s m. (Monad m, MonadState s m) => Natural (StateF s) m

A natural transformation for interpreting the state algebra as some MonadState-supporting monad. Used internally by Halogen.