Goal:
  
  G : t
  HG : acyclic_no_loop
  s : VSet.t
  x : V.t
  y1 : V.t
  y2 : V.t
  n : Z
  He : EdgeSet.In (y1, n, y2) (E G)
  Hy : VSet.In y1 s
  m : Z
  p : SPath s x y1
  Hp : sweight p = m
  p1 : SPath (VSet.remove y1 s) x y1
  p2 : SPath s y1 y1
  Hp12 : split' p = (p1, p2)
  H : sweight (split' p).1 + sweight (split' p).2 = sweight p
  ============================
   (Some m + Some n <= lsp0 s x y2)%nbar


DEBUG:Going to execute:
rewrite Hp12 in   H
DEBUG LTAC Evaluated term: (split' p)
DEBUG LTAC Evaluated term: (weight_split' p)