arc_face_graph

arc_face_graph(k)

Return the arc–face adjacency graph.

Nodes are arcs of k (as they appear in k.arcs); two arcs are adjacent if they lie on the same face.

Parameters:

k (PlanarDiagram) – Input planar diagram.

Returns:

dict – Mapping arc -> set[arc] where each value contains arcs that share at least one face with the key arc.

Return type:

dict