@jsoldi/hkt/dist/types/state.d.ts

Higher kinded types for typescript and a few utility monads.

import { $, $I, KRoot } from "../core/hkt.js";
import { IMonad } from "../classes/monad.js";
import { ITransformer } from "../classes/transformer.js";
/** The state monad transformer value type, representing a function that takes a state and returns a new state and a value wrapped in the given type `F`. */
export type StateTrans<F, S, T> = (a: S) => $<F, [T, S]>;
/** The state monad value type. */
export type State<S, T> = StateTrans<$I, S, T>;
/** Higher-kinded type of the state monad. */
export interface KState<S> extends KRoot {
    readonly 0: unknown;
    readonly body: State<S, this[0]>;
}
/** Higher-kinded type of the state monad transformer. */
export interface KStateTrans<S> extends KRoot {
    readonly 0: unknown;
    readonly 1: unknown;
    readonly body: StateTrans<this[0], S, this[1]>;
}
/** The state interface, providing stateful computations. */
export interface IState<S> extends IMonad<KState<S>>, ITransformer<KStateTrans<S>> {
    /** Produces a state that evaluates to the current state. */
    readonly get: State<S, S>;
    /** Produces a state that evaluates to the given value. */
    put<S>(s: S): State<S, null>;
    /** Creates a `state` module with a fixed environment type. */
    of<T>(): IState<T>;
}
/** The `state` module, providing a set of functions for working with state functions. The environment type is fixed to `any`. To change the environment type, call the `of` function. */
export declare const state: IState<any>;
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