(* Main properties **********************************************************)
(* Basic_1: was: drop1_trans *)
-theorem drops_trans: ∀L,L2,s,des2. ⬇*[s, des2] L ≡ L2 → ∀L1,des1. ⬇*[s, des1] L1 ≡ L →
- ⬇*[s, des2 @@ des1] L1 ≡ L2.
-#L #L2 #s #des2 #H elim H -L -L2 -des2 /3 width=3 by drops_cons/
+theorem drops_trans: ∀L,L2,s,cs2. ⬇*[s, cs2] L ≡ L2 → ∀L1,cs1. ⬇*[s, cs1] L1 ≡ L →
+ ⬇*[s, cs2 @@ cs1] L1 ≡ L2.
+#L #L2 #s #cs2 #H elim H -L -L2 -cs2 /3 width=3 by drops_cons/
qed-.