cases step with
| charStep h₁ h₂ step =>
  exact ⟨i', _ :: pcs, scs, rfl, .step (.charStep h₁ h₂ step) path, step'⟩
| εStep h₁ h₂ step =>
  exact ⟨i', pcs, scs, rfl, .step (.εStep h₁ h₂ step) path, step'⟩
case intro.intro.intro.intro.intro
nfa : NFA
i j next start : ℕ
cs₁ : List Char
step : nfa.stepIn start i j cs₁
i' : ℕ
pcs scs : List Char
path : nfa.pathIn start j i' pcs
step' : nfa.stepIn start i' next scs
⊢ nfa.pathToNext next start i (cs₁ ++ (pcs ++ scs))
no goals