fact: Definition dense (T : topologicalType) (S : set T) := forall (O : set T), O !=set0 -> open O -> O `&` S !=set0.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap generic_quotient) mathcomp(boolp classical_sets functions) mathcomp(cardinality mathcomp_extra fsbigop) reals signed