Definition SF_cut_down' (sf : @SF_seq R) (x : R) x0 :=
  let s := seq_cut_down' ((SF_h sf,x0) :: (SF_t sf)) x x0 in
  mkSF_seq (fst (head (SF_h sf,x0) s)) (behead s).Definition SF_cut_up' (sf : @SF_seq R) (x : R) x0 :=
  let s := seq_cut_up' ((SF_h sf,x0) :: (SF_t sf)) x x0 in
  mkSF_seq (fst (head (SF_h sf,x0) s)) (behead s).

Lemma ad_SF_compat z0 (s : SF_seq) (pr : SF_sorted Rle s) : adapted_couple (SF_fun s z0) (head 0 (SF_lx s)) (last 0 (SF_lx s)) (seq2Rlist (SF_lx s)) (seq2Rlist (SF_ly s)).