public static PushAggregator <T, T> Min <T, TCompare>(this IPushingEnumerator <T> source, Func <T, TCompare> selector) => new PushAggregator <T, T>(source, GetMinIterator(selector));
public static PushAggregator <T, T> Last <T>(this IPushingEnumerator <T> source) => new PushAggregator <T, T>(source, GetLastIterator <T>());
public static PushAggregator <T, int> Count <T>(this IPushingEnumerator <T> source, Func <T, bool> predicate = null) => new PushAggregator <T, int>(source, GetCountIterator(predicate));