Method immediateParent

s2/cellid.go:183–186

immediateParent is cheaper than Parent, but assumes !ci.isFace().

()

// immediateParent is cheaper than Parent, but assumes !ci.isFace().
func (ci CellID) immediateParent() CellID {
	nlsb := CellID(ci.lsb() << 2)
	return (ci & -nlsb) | nlsb
}

// isFace returns whether this is a top-level (face) cell.
func (ci CellID) isFace() bool { return uint64(ci)&(lsbForLevel(0)-1) == 0 }