Goal:
  
  A : Type
  p : nat → A → bool
  q : nat → A → bool
  n : nat
  a : A
  l : list A
  hfg : ∀ i : nat, p i =1 q i
  IHl : ∀ n : nat, alli p n l = alli q n l
  ============================
   (p n a && alli q (S n) l = q n a && alli q (S n) l)


DEBUG:Going to execute:
solve
[ trivial
with eq_true
| reflexivity
| symmetry; trivial
| contradiction
| congruence ]