foldRightWithIndex<C> method
Implementation
@override
C foldRightWithIndex<C>(C c, C Function(int i, C acc, R b) f) =>
foldRight<Tuple2<C, int>>(
Tuple2(c, length() - 1),
(t, b) => Tuple2(f(t.second, t.first, b), t.second - 1),
).first;