induction n using Nat.strongInductionOn generalizing e
V_N V_T : Type
R : V_N → PE V_N V_T
e : PE V_N V_T
xs ys : List V_T
n : ℕ
h1 : Interpretation V_N V_T R (e, xs) (n, some ys)
⊢ ys.IsPrefix xs
case ind
V_N V_T : Type
R : V_N → PE V_N V_T
xs ys : List V_T
n✝ : ℕ
a✝ : ∀ m < n✝, ∀ (e : PE V_N V_T), Interpretation V_N V_T R (e, xs) (m, some ys) → ys.IsPrefix xs
e : PE V_N V_T
h1 : Interpretation V_N V_T R (e, xs) (n✝, some ys)
⊢ ys.IsPrefix xs