Status: OUT
Visitor's structural generalization over Iterator (operating on heterogeneous type collections without requiring a common parent) provides genuinely broader extensibility only while Visitor does not break encapsulation — requiring element classes to expose internal state through their Visit interface may negate the flexibility gained by removing the common-parent constraint, trading type-hierarchy coupling for implementation coupling.
Visitor's type-heterogeneity advantage requires encapsulation preservation
Depends on (SL): gof-visitor-no-common-parent-required, iterator-separates-traversal-from-aggregate
Unless: gof-visitor-breaks-encapsulation