proposition: Lemma parxtop (x: X): x ∥ top ≡ x.
proof: Proof. symmetry. generalize (A12 1 x). by rewrite par11 2!dot1x parC. Qed.
imports: HB(structures) Coq(Setoid Morphisms) mathcomp(all_ssreflect) GraphTheory(edone preliminaries setoid_bigop structures pttdom)