Status: IN
Visitor's structure-independent stateful computation (accumulating results across heterogeneous elements without a common parent class) combined with the recursive triad's flexible traversal (Iterator's dual control and robustness axes) yields a complete extensible-computation-over-recursive-structures capability: new operations with cross-element state can be added to any recursive structure with flexible traversal control.
Visitor's accumulation + Iterator's traversal flexibility = complete recursive computation
Depends on (SL): visitor-accumulates-across-structures, recursive-triad-traversal-flexibility