That's what a zipper [1] is good for. It gives you access to the rest of a collection relative to the current position. [1] http://en.wikipedia.org/wiki/Zipper

That's what a zipper [1] is good for. It gives you access to the rest of a collection relative to the current position. [1] http://en.wikipedia.org/wiki/Zipper_%28data_structure%29 http://en.wikipedia.org/wiki/Zipper_%28data_structure%29