1 | 1. the_graph: Graph 2. L1: Vertices(the_graph) List 3. L2: Vertices(the_graph) List 4. s: traversal(the_graph) 5. L1-the_graph- > *L2 6. df-traversal(the_graph;s) & ( i:Vertices(the_graph). (inl(i) s)  L1-the_graph- > *i) 7. i:Vertices(the_graph). L1 @ L2-the_graph- > *i  non-trivial-loop(the_graph;i) 8. 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))) L1@0,L2@0:Vertices(the_graph) List. (L1 @ L2) = (L1@0 @ L2@0)  ( 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@0-the_graph- > *j & L1@0-the_graph- > *j))) | 18 steps |