change (M.ModularPair X Y ∧ _) ↔ _
ι : Type u_1
α : Type u_2
M : Matroid α
B I J X✝ X' Y✝ Y' F : Set α
Xs Ys Js Is : ι → Set α
i j : ι
e f : α
X Y : Set α
⊢ M.Skew X Y ↔ ∃ I J, M.Indep (I ∪ J) ∧ Disjoint I J ∧ M.Basis I X ∧ M.Basis J Y
ι : Type u_1
α : Type u_2
M : Matroid α
B I J X✝ X' Y✝ Y' F : Set α
Xs Ys Js Is : ι → Set α
i j : ι
e f : α
X Y : Set α
⊢ (M.ModularPair X Y ∧
      ∀ ⦃i j : Bool⦄, i ≠ j → (fun i => bif i then X else Y) i ∩ (fun i => bif i then X else Y) j ⊆ M.cl ∅) ↔
    ∃ I J, M.Indep (I ∪ J) ∧ Disjoint I J ∧ M.Basis I X ∧ M.Basis J Y