interpretation "cons (list of pairs)" 'Cons hd1 hd2 tl = (cons2 ? ? hd1 hd2 tl).
-let rec append2 (A1,A2:Type[0]) (l1,l2:list2 A1 A2) on l1 ≝ match l1 with
+rec definition append2 (A1,A2:Type[0]) (l1,l2:list2 A1 A2) on l1 ≝ match l1 with
[ nil2 ⇒ l2
| cons2 a1 a2 tl ⇒ {a1, a2} @ append2 A1 A2 tl l2
].
interpretation "append (list of pairs)"
'Append l1 l2 = (append2 ? ? l1 l2).
-let rec length2 (A1,A2:Type[0]) (l:list2 A1 A2) on l ≝ match l with
+rec definition length2 (A1,A2:Type[0]) (l:list2 A1 A2) on l ≝ match l with
[ nil2 ⇒ 0
| cons2 _ _ l ⇒ ⫯(length2 A1 A2 l)
].