/3 width=4 by lfxs_gref, tc_lfxs_step_dx, inj/
qed.
-lemma tc_lfxs_sym: ∀R. lexs_frees_confluent (cext2 R) cfull →
- (∀L1,L2,T1,T2. R L1 T1 T2 → R L2 T2 T1) →
- ∀T. symmetric … (tc_lfxs R T).
-#R #H1R #H2R #T #L1 #L2 #H elim H -L2
-/4 width=3 by lfxs_sym, tc_lfxs_step_sn, inj/
-qed-.
-
lemma tc_lfxs_co: ∀R1,R2. (∀L,T1,T2. R1 L T1 T2 → R2 L T1 T2) →
∀L1,L2,T. L1 ⪤**[R1, T] L2 → L1 ⪤**[R2, T] L2.
#R1 #R2 #HR #L1 #L2 #T #H elim H -L2