Stack depth: O(1). The operator is called from C++, returns a list, and the C++ loop calls it again. Nix call frames don't accumulate.
option navigation (default false). When navigation is set, zoomed splits
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沙特國防部表示，數小時前，兩架無人機擊中沙特阿拉伯首都利雅得（Riyadh）的美國大使館，引發「小規模火災」。
(B) delays updating for now, knowing there are other dependencies to update first. Meanwhile, (C) updates, and pushes a signal on to (B) and (D).