reserve G,G1,G2 for _Graph;
reserve e,x,y for set;
reserve v,v1,v2 for Vertex of G;
reserve W for Walk of G;

theorem
  for G being acyclic _Graph, W being Path of G, e being set st not e in
W.edges() & e in W.last().edgesInOut() holds W.addEdge(e) is Path-like by Lm22;
