/**
 * Type of the key used in the LRU.
 *
 * @public
 */
export type Key = string | number;
/**
 * Cache evicts the least-recently-used key when capacity is exceeded.
 *
 * @public
 */
export declare class LRU<V> {
    private readonly storage;
    private readonly root;
    private readonly capacity;
    constructor(capacity?: number);
    /**
     * Number of items in the LRU.
     */
    size(): number;
    /**
     * Get the value associated with the key and move the
     * key to the front of the LRU.
     */
    get(key: Key): V | undefined;
    /**
     * Set a value associated with the key. IF it already
     * exists, the value is updated. Otherwise it is inserted
     * into the LRU and moved to the front.
     */
    set(key: Key, val: V): void;
    /**
     * Show the contents of the LRU as a string.
     */
    toString(): string;
    private moveFront;
    private insert;
    private remove;
}