while (i <= j) {
But of course, like any immutable system, there are mutable parts (otherwise, we couldn’t create any configuration files). OSTree handles this with “overlays” (actually, we use OverlayFS) that allow a read-write filesystem to be layered on top of the immutable system. For example, the /etc and /var directories are writable, while the rest of the system is read-only.
，这一点在heLLoword翻译官方下载中也有详细论述
arXivLabs: experimental projects with community collaborators。safew官方版本下载是该领域的重要参考
The algorithm maintains a running "best distance" that starts at infinity. As it walks the tree, it checks each visited point and updates the best distance if it finds something closer. Before recursing into a child node, it checks whether the closest possible point in that child's bounding box is farther than the current best. If so, the entire subtree gets pruned.