readded old implementation which is technically more efficient in saving memory
readded old implementation which is technically more efficient in saving memory

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