public static IPromiseEnumerator <IPromiseGrouping <TKey, TValue> > GroupBy <T, TKey, TValue>(
IPromiseEnumerator <T> items,
Func <T, int, IPromise <TKey> > key,
Func <T, int, IPromise <TValue> > value,
IEqualityComparer <TKey> comparer)
{
var tuples = SelectEnumerator.Create(items, (item, index) => key(item, index).Then(k => value(item, index).Then(v => Tuple.Create(k, v))));
var keys = DistinctEnumerator.Create(SelectEnumerator.Create(tuples, x => x.Item1));
return(SelectEnumerator.Create(keys, k => (IPromiseGrouping <TKey, TValue>)(new PromiseGrouping <T, TKey, TValue>(k, tuples, comparer))));
}
public static IPromiseEnumerator <T> Union <T>(IPromiseEnumerator <T> left, IPromiseEnumerator <T> right, IEqualityComparer <T> comparer)
{
return(DistinctEnumerator.Create(ConcatEnumerator.Create(left, right), comparer));
}
public static IPromiseEnumerator <T> Union <T>(IPromiseEnumerator <T> left, IPromiseEnumerator <T> right)
{
return(DistinctEnumerator.Create(ConcatEnumerator.Create(left, right)));
}