Research proof index

Multiple reduction of opening implies multiple reduction of abstraction. -/ theorem redex_abs_cong {M M' : Term Var} (xs : Finset Var) (cofin : ∀ x ∉ xs, (M ^ fvar x) ↠ηᶠ M' ^ fvar x) (lc_M : LC M.abs) : M.abs ↠ηᶠ M'.abs := by cases lc_M case abs L hL => have ⟨x, _⟩ := fresh_exists <| free_union [fv] Var rw [open_close x M 0, open_close x M' 0] all_goals...