/**
 * A type used to express actions in the loop.
 * Each action can have a value with it.
 * @typeparam A - Type of step results.
 * @typeparam B - Type of finish results.
 * @typeparam E - Type of errors.
 */
export declare type LoopAction<A, B, E> = Step<A> | Finish<B> | Fail<E>;
/**
 * Tag for the loop action variants.
 */
export declare enum LoopTag {
    STEP = "step",
    FINISH = "finish",
    FAIL = "fail"
}
/**
 * The loop should continue being stepped through.
 * @typeparam A - Type of step results.
 */
export interface Step<A> {
    /**
     * If this is a Step, this is 'step'.
     */
    readonly action: LoopTag.STEP;
    /**
     * The item to step with.
     */
    readonly item: A;
    readonly value?: undefined;
    readonly error?: undefined;
}
/**
 * The loop should finish successfully.
 * @typeparam B - Type of finish results.
 */
export interface Finish<B> {
    /**
     * If this is a Finish, this is 'finish'.
     */
    readonly action: LoopTag.FINISH;
    readonly item?: undefined;
    /**
     * The resulting value.
     */
    readonly value: B;
    readonly error?: undefined;
}
/**
 * The loop should fail due to an error.
 * @typeparam E - Type of errors.
 */
export interface Fail<E> {
    /**
     * If this is a Fail, this is 'fail'.
     */
    readonly action: LoopTag.FAIL;
    readonly item?: undefined;
    readonly value?: undefined;
    /**
     * The resulting error.
     */
    readonly error: E;
}
/**
 * Creates a Step.
 * @typeparam A - Type of step results.
 * @param x - Value to use.
 * @returns A LoopAction.
 */
export declare function step<A>(x: A): Step<A>;
/**
 * Creates a Step with null value.
 * @returns A LoopAction.
 */
export declare function step_(): Step<null>;
/**
 * Creates a Finish.
 * @typeparam B - Type of finish results.
 * @param x - Value to use.
 * @returns A LoopAction.
 */
export declare function finish<B>(x: B): Finish<B>;
/**
 * Creates a Fail.
 * @typeparam E - Type of errors.
 * @param x - Value to use.
 * @returns A LoopAction.
 */
export declare function fail<E>(x: E): Fail<E>;
/**
 * Creates a Fail with null value.
 * @returns A LoopAction.
 */
export declare function fail_(): Fail<null>;