use separator.join() in make_string
use separator.join() in make_string

ChuyuHsu/ScalaFunctional,ChuyuHsu/ScalaFunctional,lucidfrontier45/ScalaFunctional,EntilZha/PyFunctional,lucidfrontier45/ScalaFunctional,EntilZha/ScalaFunctional,EntilZha/ScalaFunctional,EntilZha/PyFunctional