Module: Mathlib.Data.Seq.Parallel

Goal state before:
pp: case cons.inr
α : Type u
lem1 :
  ∀ (l : List (Computation α)) (S : WSeq (Computation α)),
    (∃ a, parallel.aux2 l = Sum.inl a) → (corec parallel.aux1 (l, S)).Terminates
c✝ : Computation α
T : c✝.Terminates
s : Computation α
IH : ∀ {l : List (Computation α)} {S : WSeq (Computation α)}, s ∈ l → (corec parallel.aux1 (l, S)).Terminates
S : WSeq (Computation α)
c : Computation α
l : List (Computation α)
IH' : s.think ∈ l → ∀ (l' : List (Computation α)), parallel.aux2 l = Sum.inr l' → s ∈ l'
l' : List (Computation α)
e' :
  (match
      List.foldr
        (fun c o ↦
          match o with
          | Sum.inl a => Sum.inl a
          | Sum.inr ls =>
            match c.destruct with
            | Sum.inl a => Sum.inl a
            | Sum.inr b => Sum.inr (b :: ls))
        (Sum.inr []) l with
    | Sum.inl a => Sum.inl a
    | Sum.inr ls =>
      match c.destruct with
      | Sum.inl a => Sum.inl a
      | Sum.inr b => Sum.inr (b :: ls)) =
    Sum.inr l'
m : s.think ∈ l
⊢ s ∈ l'

Tactic:
rcases e : List.foldr (fun c o =>
            match o with
            | Sum.inl a => Sum.inl a
            | Sum.inr ls => rmap (fun c' => c' :: ls) (destruct c))
          (Sum.inr List.nil) l with a' | ls <;> simp only [rmap] at e <;> rw [e] at e'

Goal state after:
case cons.inr.inl
α : Type u
lem1 :
  ∀ (l : List (Computation α)) (S : WSeq (Computation α)),
    (∃ a, parallel.aux2 l = Sum.inl a) → (corec parallel.aux1 (l, S)).Terminates
c✝ : Computation α
T : c✝.Terminates
s : Computation α
IH : ∀ {l : List (Computation α)} {S : WSeq (Computation α)}, s ∈ l → (corec parallel.aux1 (l, S)).Terminates
S : WSeq (Computation α)
c : Computation α
l : List (Computation α)
IH' : s.think ∈ l → ∀ (l' : List (Computation α)), parallel.aux2 l = Sum.inr l' → s ∈ l'
l' : List (Computation α)
m : s.think ∈ l
a' : α
e' :
  (match Sum.inl a' with
    | Sum.inl a => Sum.inl a
    | Sum.inr ls =>
      match c.destruct with
      | Sum.inl a => Sum.inl a
      | Sum.inr b => Sum.inr (b :: ls)) =
    Sum.inr l'
e :
  List.foldr
      (fun c o ↦
        match o with
        | Sum.inl a => Sum.inl a
        | Sum.inr ls =>
          match c.destruct with
          | Sum.inl a => Sum.inl a
          | Sum.inr b => Sum.inr (b :: ls))
      (Sum.inr []) l =
    Sum.inl a'
⊢ s ∈ l'

case cons.inr.inr
α : Type u
lem1 :
  ∀ (l : List (Computation α)) (S : WSeq (Computation α)),
    (∃ a, parallel.aux2 l = Sum.inl a) → (corec parallel.aux1 (l, S)).Terminates
c✝ : Computation α
T : c✝.Terminates
s : Computation α
IH : ∀ {l : List (Computation α)} {S : WSeq (Computation α)}, s ∈ l → (corec parallel.aux1 (l, S)).Terminates
S : WSeq (Computation α)
c : Computation α
l : List (Computation α)
IH' : s.think ∈ l → ∀ (l' : List (Computation α)), parallel.aux2 l = Sum.inr l' → s ∈ l'
l' : List (Computation α)
m : s.think ∈ l
ls : List (Computation α)
e' :
  (match Sum.inr ls with
    | Sum.inl a => Sum.inl a
    | Sum.inr ls =>
      match c.destruct with
      | Sum.inl a => Sum.inl a
      | Sum.inr b => Sum.inr (b :: ls)) =
    Sum.inr l'
e :
  List.foldr
      (fun c o ↦
        match o with
        | Sum.inl a => Sum.inl a
        | Sum.inr ls =>
          match c.destruct with
          | Sum.inl a => Sum.inl a
          | Sum.inr b => Sum.inr (b :: ls))
      (Sum.inr []) l =
    Sum.inr ls
⊢ s ∈ l'