///
bool idxUpDown(Cursor & cur, bool up) const;
///
bool idxForward(Cursor & cur) const;
///
bool idxBackward(Cursor & cur) const;
///
bool idxUpDown(Cursor & cur, bool up) const;
///
bool idxForward(Cursor & cur) const;
///
bool idxBackward(Cursor & cur) const;