/**
 * A dead-simple cache helper.
 */
export declare class SimpleCache<K, V> {
    private readonly gen;
    private readonly m;
    constructor(gen: (k: K) => V);
    /**
     * Copies this as a regular {@link Map}.
     */
    copy(): Map<K, V>;
    has(k: K): boolean;
    get(k: K): V;
    get size(): number;
    clear(): void;
    keys(): MapIterator<K>;
    entries(): MapIterator<[K, V]>;
    values(): MapIterator<V>;
    delete(k: K): boolean;
}
/**
 * Return a helper which runs the passed function at most once.
 */
export declare function once<T = void>(fn: () => T): () => T;
/**
 * Lazy {@link WeakMap} factory.
 */
export declare function lazyWeak<W extends Object, V>(fn: (w: W) => V): (w: W) => V;