reserve G,G1,G2 for _Graph;
reserve W,W1,W2 for Walk of G;
reserve e,x,y,z for set;
reserve v for Vertex of G;
reserve n,m for Element of NAT;

theorem
  len W = len W.reverse() & dom W = dom W.reverse() & rng W = rng W
  .reverse() by FINSEQ_5:57,def 3;
