State overview
The State monad is a synonym for the StateT monad transformer, applied to the Identity monad.
For a good introduction to the state monad, see the following blog post by @pfgray: The State monad
Added in v2.0.0
Table of contents
- State (interface)
- URI (type alias)
- URI (constant)
- evalState (constant)
- execState (constant)
- get (constant)
- gets (constant)
- modify (constant)
- of (constant)
- put (constant)
- state (constant)
- ap (export)
- apFirst (export)
- apSecond (export)
- chain (export)
- chainFirst (export)
- flatten (export)
- map (export)
State (interface)
Signature
export interface State<S, A> {
(s: S): [A, S]
}
Added in v2.0.0
URI (type alias)
Signature
export type URI = typeof URI
Added in v2.0.0
URI (constant)
Signature
export const URI: "State" = ...
Added in v2.0.0
evalState (constant)
Run a computation in the State monad, discarding the final state
Signature
export const evalState: <S, A>(ma: State<S, A>, s: S) => A = ...
Added in v2.0.0
execState (constant)
Run a computation in the State monad discarding the result
Signature
export const execState: <S, A>(ma: State<S, A>, s: S) => S = ...
Added in v2.0.0
get (constant)
Get the current state
Signature
export const get: <S>() => State<S, S> = ...
Added in v2.0.0
gets (constant)
Get a value which depends on the current state
Signature
export const gets: <S, A>(f: (s: S) => A) => State<S, A> = ...
Added in v2.0.0
modify (constant)
Modify the state by applying a function to the current state
Signature
export const modify: <S>(f: (s: S) => S) => State<S, void> = ...
Added in v2.0.0
of (constant)
Signature
export const of: <S, A>(a: A) => State<S, A> = ...
Added in v2.0.0
put (constant)
Set the state
Signature
export const put: <S>(s: S) => State<S, void> = ...
Added in v2.0.0
state (constant)
Signature
export const state: Monad2<URI> = ...
Added in v2.0.0
ap (export)
Signature
<E, A>(fa: State<E, A>) => <B>(fab: State<E, (a: A) => B>) => State<E, B>
Added in v2.0.0
apFirst (export)
Signature
<E, B>(fb: State<E, B>) => <A>(fa: State<E, A>) => State<E, A>
Added in v2.0.0
apSecond (export)
Signature
<E, B>(fb: State<E, B>) => <A>(fa: State<E, A>) => State<E, B>
Added in v2.0.0
chain (export)
Signature
<E, A, B>(f: (a: A) => State<E, B>) => (ma: State<E, A>) => State<E, B>
Added in v2.0.0
chainFirst (export)
Signature
<E, A, B>(f: (a: A) => State<E, B>) => (ma: State<E, A>) => State<E, A>
Added in v2.0.0
flatten (export)
Signature
<E, A>(mma: State<E, State<E, A>>) => State<E, A>
Added in v2.0.0
map (export)
Signature
<A, B>(f: (a: A) => B) => <E>(fa: State<E, A>) => State<E, B>
Added in v2.0.0