[zxzavhsm] Maps by search

Consider a polygonal mesh stored as a half-edge data structure.  In order to do a "map" or "foreach" operation on all faces (or E or V), one can do search (e.g., depth-first search) over the graph to find all the faces.

There is nothing wrong with this, though it may be a mental block to do something seemingly far more expensive than incrementing an index or following a pointer to iterate over a data structure.

Thinking about how to handle a hexagonal grid.