Goal:
  
  A : Type
  P : nat → A → A → Type
  i : nat
  l : list A
  tl : list A
  tl' : list A
  ============================
   (OnOne2i P (#|l| + i) tl tl' → OnOne2i P i (l ++ tl) (l ++ tl'))


DEBUG:Going to execute:
induction l in i |- *

Goals:
    A : Type  P : nat → A → A → Type  i : nat  tl : list A  tl' : list A
  ============================
   (OnOne2i P (#|[]| + i) tl tl' → OnOne2i P i ([] ++ tl) ([] ++ tl'))

  
  A : Type
  P : nat → A → A → Type
  i : nat
  a : A
  l : list A
  tl : list A
  tl' : list A
  IHl : ∀ i : nat,
          OnOne2i P (#|l| + i) tl tl' → OnOne2i P i (l ++ tl) (l ++ tl')
  ============================
   (OnOne2i P (#|a :: l| + i) tl tl'
    → OnOne2i P i ((a :: l) ++ tl) ((a :: l) ++ tl'))


DEBUG:Going to execute:
simpl
DEBUG LTAC Evaluated term: l

Goals:
    A : Type  P : nat → A → A → Type  i : nat  tl : list A  tl' : list A
  ============================
   (OnOne2i P i tl tl' → OnOne2i P i tl tl')

  
  A : Type
  P : nat → A → A → Type
  i : nat
  a : A
  l : list A
  tl : list A
  tl' : list A
  IHl : ∀ i : nat,
          OnOne2i P (#|l| + i) tl tl' → OnOne2i P i (l ++ tl) (l ++ tl')
  ============================
   (OnOne2i P (S (#|l| + i)) tl tl'
    → OnOne2i P i (a :: l ++ tl) (a :: l ++ tl'))


DEBUG:Going to execute:
try constructor