Inductive eql_t0 : list K -> list K -> Prop :=
  eql_t0N: eql_t0 nil nil
| eql_t0Nl: forall l, eql_t0 l nil -> eql_t0 (0%f :: l) nil
| eql_t0Nr: forall l, eql_t0 nil l -> eql_t0 nil (0%f :: l) 
| eql_t0R: forall a l1 l2, eql_t0 l1 l2 -> eql_t0 (a :: l1) (a :: l2).Inductive eql_t0 : list K -> list K -> Prop :=
  eql_t0N: eql_t0 nil nil
| eql_t0Nl: forall l, eql_t0 l nil -> eql_t0 (0%f :: l) nil
| eql_t0Nr: forall l, eql_t0 nil l -> eql_t0 nil (0%f :: l) 
| eql_t0R: forall a l1 l2, eql_t0 l1 l2 -> eql_t0 (a :: l1) (a :: l2).Inductive eql_t0 : list K -> list K -> Prop :=
  eql_t0N: eql_t0 nil nil
| eql_t0Nl: forall l, eql_t0 l nil -> eql_t0 (0%f :: l) nil
| eql_t0Nr: forall l, eql_t0 nil l -> eql_t0 nil (0%f :: l) 
| eql_t0R: forall a l1 l2, eql_t0 l1 l2 -> eql_t0 (a :: l1) (a :: l2).Inductive eql_t0 : list K -> list K -> Prop :=
  eql_t0N: eql_t0 nil nil
| eql_t0Nl: forall l, eql_t0 l nil -> eql_t0 (0%f :: l) nil
| eql_t0Nr: forall l, eql_t0 nil l -> eql_t0 nil (0%f :: l) 
| eql_t0R: forall a l1 l2, eql_t0 l1 l2 -> eql_t0 (a :: l1) (a :: l2).Inductive eql_t0 : list K -> list K -> Prop :=
  eql_t0N: eql_t0 nil nil
| eql_t0Nl: forall l, eql_t0 l nil -> eql_t0 (0%f :: l) nil
| eql_t0Nr: forall l, eql_t0 nil l -> eql_t0 nil (0%f :: l) 
| eql_t0R: forall a l1 l2, eql_t0 l1 l2 -> eql_t0 (a :: l1) (a :: l2).

Lemma eql_sym l1 l2 : eql_t0 l1 l2 -> eql_t0 l2 l1.