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:
symmetry; trivial
Level 1: Backtrace:

In environment
A : Type
p, 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
Unable to unify "q n a && alli q (S n) l" with "p n a && alli q (S n) l".
Level 0: Backtrace:

In environment
A : Type
p, 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
Unable to unify "q n a && alli q (S n) l" with "p n a && alli q (S n) l".