proposition: Lemma eq_gpath (e1 e2 : rel T) t1 t2 c : e1 =2 e2 -> gpath e1 t1 t2 c = gpath e2 t1 t2 c.
proof: Proof. by move=> e1Ee2; apply/gpathP/gpathP; rewrite (eq_path e1Ee2) (eq_dist e1Ee2). Qed.
imports: mathcomp(all_ssreflect)