/2 width=5 by tsts_inv_gref1_aux/ qed-.
fact tsts_inv_pair1_aux: ∀h,o,T1,T2. T1 ⩳[h, o] T2 →
- ∀I,W1,U1. T1 = ②{I}W1.U1 →
- ∃∃W2,U2. T2 = ②{I}W2.U2.
+ ∀J,W1,U1. T1 = ②{J}W1.U1 →
+ ∃∃W2,U2. T2 = ②{J}W2.U2.
#h #o #T1 #T2 * -T1 -T2
[ #s1 #s2 #d #_ #_ #J #W1 #U1 #H destruct
| #i #J #W1 #U1 #H destruct
∃∃W2,U2. T2 = ②{J}W2. U2.
/2 width=7 by tsts_inv_pair1_aux/ qed-.
+fact tsts_inv_pair2_aux: ∀h,o,T1,T2. T1 ⩳[h, o] T2 →
+ ∀J,W2,U2. T2 = ②{J}W2.U2 →
+ ∃∃W1,U1. T1 = ②{J}W1.U1.
+#h #o #T1 #T2 * -T1 -T2
+[ #s1 #s2 #d #_ #_ #J #W2 #U2 #H destruct
+| #i #J #W2 #U2 #H destruct
+| #l #J #W2 #U2 #H destruct
+| #I #V1 #V2 #T1 #T2 #J #W2 #U2 #H destruct /2 width=3 by ex1_2_intro/
+]
+qed-.
+
+lemma tsts_inv_pair2: ∀h,o,J,T1,W2,U2. T1 ⩳[h, o] ②{J}W2.U2 →
+ ∃∃W1,U1. T1 = ②{J}W1.U1.
+/2 width=7 by tsts_inv_pair2_aux/ qed-.
+
(* Advanced inversion lemmas ************************************************)
lemma tsts_inv_sort1_deg: ∀h,o,Y,s1. ⋆s1 ⩳[h, o] Y → ∀d. deg h o s1 d →