Goal:
  
  A : Type
  f : nat → A
  n : nat
  i : nat
  hf : ∀ i j : nat, f i = f j → i = j
  ============================
   (In (f i) (unfold n f) → i < n)


DEBUG:Going to execute:
induction n

Goals:
    A : Type  f : nat → A  i : nat  hf : ∀ i j : nat, f i = f j → i = j
  ============================
   (In (f i) (unfold 0 f) → i < 0)

  
  A : Type
  f : nat → A
  n : nat
  i : nat
  hf : ∀ i j : nat, f i = f j → i = j
  IHn : In (f i) (unfold n f) → i < n
  ============================
   (In (f i) (unfold (S n) f) → i < S n)


DEBUG:Going to execute:
simpl => //
DEBUG LTAC Evaluated term: n