letin spec ≝ (λz,k:nat.∀i,j,l:nat.k ≤ i → k ≤ j → l ≤ z → w l 〈a i,a j〉);
letin m ≝ (hide ? (let rec aux (i:nat) : nat ≝
match i with
letin spec ≝ (λz,k:nat.∀i,j,l:nat.k ≤ i → k ≤ j → l ≤ z → w l 〈a i,a j〉);
letin m ≝ (hide ? (let rec aux (i:nat) : nat ≝
match i with