1 | 15. l_disjoint(Vertices(the_graph)+Vertices(the_graph);s2;s1) 16. no_repeats(Vertices(the_graph)+Vertices(the_graph);s2) 17. paren(Vertices(the_graph);s2) 18. j:Vertices(the_graph). (inr(j) s2)  i1-the_graph- > *j 19. x,y:Vertices(the_graph). the_obj.eq(x,y)  x = y 20. T:Type, s:T, x:Vertices(the_graph), f:(T Vertices(the_graph) T).
L:Vertices(the_graph) List.
( y:Vertices(the_graph). x-the_graph- > y  (y L))
& the_obj.eacc(f,s,x) = list_accum(s',x'.f(s',x');s;L) 21. T:Type, s:T, f:(T Vertices(the_graph) T).
L:Vertices(the_graph) List.
no_repeats(Vertices(the_graph);L)
& ( y:Vertices(the_graph). (y L))
& the_obj.vacc(f,s) = list_accum(s',x'.f(s',x');s;L) 22. (inl(i1) s1) (inr(i1) s2) | 1 step |