public T Reduce(TupledFunction <T, T, T> f, T id) => Reduce(f._f, id);
public U Iter <U>(TupledFunction <U, T, U> f, U init) => Iter(f._f, init);
public Sequence <U> MapIndex <U>(TupledFunction <int, T, U> f) => MapIndex(f._f);
public Sequence <V> MapWith <U, V>(Sequence <U> other, TupledFunction <T, U, V> f) => MapWith(other, f._f);
public Sequence <T> FilterIdx(TupledFunction <int, T, bool> predicate) => FilterIdx(predicate._f);