/** Maps keys to counters. **/
export declare class CounterMap<T> extends Map<T, number> {
	/**
	 * Retreive the value mapped to a key.
	 * @returns the value, or 0 if NaN
	 */
	get(key: T): number;
	/**
	 * increment a counter
	 * @returns the counter's new value
	 */
	increment(key: T): number;
	/**
	 * decrement a counter
	 * @returns the counter's new value
	 */
	decrement(key: T): number;
	/**
	 * reset a counter
	 * @returns the counter's new value = 0
	 */
	reset(key: T): number;
}
export default CounterMap;