Thm* t:Graph. Incidence(t) Edges(t) Vertices(t) Vertices(t) | [gr_f_wf] |
Def G H == vmap:(Vertices(G) Vertices(H)), emap:(Edges(G) Edges(H)). Bij(Vertices(G); Vertices(H); vmap) & Bij(Edges(G); Edges(H); emap) & (vmap,vmap) o Incidence(G) = Incidence(H) o emap | [graph-isomorphic] |
Def x-the_graph- > y == e:Edges(the_graph). Incidence(the_graph)(e) = < x,y > | [edge] |