Re: [Haskell-cafe] Circular pure data structures?

On Wed, Jul 15, 2009 at 12:13 AM, Eugene Kirpichov wrote:

Zippers come up as the "derivative" of the type; if you haven't yet encountered this trick, then first find it :)

Try differentiating your datastructure.

Here's a paper with a good introduction to the concept and bibliography: http://strictlypositive.org/dfordata.pdf My take on it: A zipper is the one-hole-context of your data-type plus a focused-on payload. Data-structure differentiation is the method for deriving the one-hole-context. Antoine