Status: IN
NullIterator is the mechanism that makes the GoF's preferred transparency approach practical for recursive structures: by providing an iterator whose IsDone always returns true, leaf nodes participate uniformly in tree traversal without null checks, directly enabling Composite's uniform treatment principle at the traversal layer.
NullIterator concretely implements the transparency design choice for leaves in recursive traversal
Depends on (SL): null-iterator-always-done, composite-gof-emphasizes-transparency