Goal:
  
  A : Type
  B : Type
  f : A → B
  l : nat
  IHn : ∀ l0 : list A, map f (skipn l l0) = skipn l (map f l0)
  ============================
   (∀ (a : A) (l0 : list A),
      map f (skipn (S l) (a :: l0)) = skipn (S l) (map f (a :: l0)))


DEBUG:Going to execute:
<coq-core.plugins.ltac::trivial@0> $1 $2

Goals:

DEBUG:Going to execute:
hnf

Goals:

DEBUG:Going to execute:
intros

Goals:

DEBUG:Going to execute:
solve
[ do
![ solve
 [ trivial | apply : eq_sym ; trivial ]
 | discriminate
 | contradiction
 | Ltac.split ]
| case not_locked_false_eq_true; Ltac.assumption
| match goal with
  | H:¬ _ |- _ => solve [ case H; trivial ]
  end ]