Module: Mathlib.Computability.Primrec.List

Goal state before:
pp: case succ
β : Type u_2
σ : Type u_4
inst✝¹ : Primcodable β
inst✝ : Primcodable σ
f : β → σ
m : β → ℕ
l : β → List β
g : β → List σ → Option σ
hm : Primrec m
hl : Primrec l
hg : Primrec₂ g
Ord : ∀ (b b' : β), b' ∈ l b → m b' < m b
H : ∀ (b : β), g b (List.map f (l b)) = some (f b)
this✝ : DecidableEq β
mapGraph : List (β × σ) → List β → List σ := fun M bs ↦ List.flatMap (fun x ↦ (List.lookup x M).toList) bs
bindList : β → ℕ → List β := fun b n ↦ Nat.rec [b] (fun x bs ↦ List.flatMap l bs) n
graph : β → ℕ → List (β × σ) :=
  fun b i ↦
    Nat.rec []
      (fun i ih ↦
        List.filterMap (fun b' ↦ Option.map (fun x ↦ (b', x)) (g b' (mapGraph ih (l b')))) (bindList b (m b - i)))
      i
mapGraph_primrec : Primrec₂ mapGraph
bindList_primrec : Primrec₂ bindList
graph_primrec : Primrec₂ graph
this : Primrec fun b ↦ Option.map Prod.snd (graph b (m b + 1))[0]?
b : β
bindList_eq_nil : bindList b (m b + 1) = []
mapGraph_graph : ∀ {bs bs' : List β}, bs' ⊆ bs → mapGraph (List.map (fun x ↦ (x, f x)) bs) bs' = List.map f bs'
graph_succ :
  ∀ (i : ℕ),
    graph b (i + 1) =
      List.filterMap (fun b' ↦ Option.map (fun x ↦ (b', x)) (g b' (mapGraph (graph b i) (l b')))) (bindList b (m b - i))
bindList_succ : ∀ (i : ℕ), bindList b (i + 1) = List.flatMap l (bindList b i)
i : ℕ
ih : i ≤ m b + 1 → graph b i = List.map (fun x ↦ (x, f x)) (bindList b (m b + 1 - i))
hi : i + 1 ≤ m b + 1
⊢ graph b (i + 1) = List.map (fun x ↦ (x, f x)) (bindList b (m b + 1 - (i + 1)))

Tactic:
simp only [graph_succ, ih (Nat.le_of_lt hi), Nat.succ_sub (Nat.le_of_lt_succ hi),
          Nat.succ_eq_add_one, bindList_succ, Nat.reduceSubDiff]

Goal state after:
case succ
β : Type u_2
σ : Type u_4
inst✝¹ : Primcodable β
inst✝ : Primcodable σ
f : β → σ
m : β → ℕ
l : β → List β
g : β → List σ → Option σ
hm : Primrec m
hl : Primrec l
hg : Primrec₂ g
Ord : ∀ (b b' : β), b' ∈ l b → m b' < m b
H : ∀ (b : β), g b (List.map f (l b)) = some (f b)
this✝ : DecidableEq β
mapGraph : List (β × σ) → List β → List σ := fun M bs ↦ List.flatMap (fun x ↦ (List.lookup x M).toList) bs
bindList : β → ℕ → List β := fun b n ↦ Nat.rec [b] (fun x bs ↦ List.flatMap l bs) n
graph : β → ℕ → List (β × σ) :=
  fun b i ↦
    Nat.rec []
      (fun i ih ↦
        List.filterMap (fun b' ↦ Option.map (fun x ↦ (b', x)) (g b' (mapGraph ih (l b')))) (bindList b (m b - i)))
      i
mapGraph_primrec : Primrec₂ mapGraph
bindList_primrec : Primrec₂ bindList
graph_primrec : Primrec₂ graph
this : Primrec fun b ↦ Option.map Prod.snd (graph b (m b + 1))[0]?
b : β
bindList_eq_nil : bindList b (m b + 1) = []
mapGraph_graph : ∀ {bs bs' : List β}, bs' ⊆ bs → mapGraph (List.map (fun x ↦ (x, f x)) bs) bs' = List.map f bs'
graph_succ :
  ∀ (i : ℕ),
    graph b (i + 1) =
      List.filterMap (fun b' ↦ Option.map (fun x ↦ (b', x)) (g b' (mapGraph (graph b i) (l b')))) (bindList b (m b - i))
bindList_succ : ∀ (i : ℕ), bindList b (i + 1) = List.flatMap l (bindList b i)
i : ℕ
ih : i ≤ m b + 1 → graph b i = List.map (fun x ↦ (x, f x)) (bindList b (m b + 1 - i))
hi : i + 1 ≤ m b + 1
⊢ List.filterMap
      (fun x ↦
        Option.map (fun x_1 ↦ (x, x_1))
          (g x (mapGraph (List.map (fun x ↦ (x, f x)) (List.flatMap l (bindList b (m b - i)))) (l x))))
      (bindList b (m b - i)) =
    List.map (fun x ↦ (x, f x)) (bindList b (m b - i))