2 | 9. df-traversal(the_graph;s) 10. i:Vertices(the_graph). (inl(i) s)  L1-the_graph- > *i 11. ( i:Vertices(the_graph). L1-the_graph- > *i  non-trivial-loop(the_graph;i))

( L1@0,L2:Vertices(the_graph) List.
L1 = (L1@0 @ L2)

( s1,s2:traversal(the_graph).
s = (s2 @ s1) traversal(the_graph)
& paren(Vertices(the_graph);s1) & paren(Vertices(the_graph);s2)
& ( j:Vertices(the_graph).
((inl(j) s1)  L1@0-the_graph- > *j)
& ((inl(j) s2)  L2-the_graph- > *j & L1@0-the_graph- > *j)))) 12. (inl(i) s) 13. s2: traversal(the_graph) 14. l_disjoint(Vertices(the_graph)+Vertices(the_graph);s2;s) 15. paren(Vertices(the_graph);s2) 16. no_repeats(Vertices(the_graph)+Vertices(the_graph);s2) 17. (inr(i) s2) 18. j:Vertices(the_graph). (inr(j) s2)  i-the_graph- > *j 19. df-traversal(the_graph;([inl(i)] @ s2 @ [inr(i)]) @ s) 20. i@0:Vertices(the_graph). L1 @ [i]-the_graph- > *i@0  non-trivial-loop(the_graph;i@0) L1@0,L2:Vertices(the_graph) List. (L1 @ [i]) = (L1@0 @ L2)  ( s1,s2@0:traversal(the_graph). (([inl(i)] @ s2 @ [inr(i)]) @ s) = (s2@0 @ s1) traversal(the_graph) & paren(Vertices(the_graph);s1) & paren(Vertices(the_graph);s2@0) & ( j:Vertices(the_graph). ((inl(j) s1)  L1@0-the_graph- > *j) & ((inl(j) s2@0)  L2-the_graph- > *j & L1@0-the_graph- > *j))) | 135 steps |