Archived version with the images still there... https://web.archive.org/web/20160328032556/http://www.goodmath.org/blog/2010/01/13/zippers-making-functional-up

Archived version with the images still there... https://web.archive.org/web/20160328032556/http://www.goodmath.org/blog/2010/01/13/zippers-making-functional-updates-efficient/ https://web.archive.org/web/20160328032556/http://www.goodma...