Hello all-<br><br>I&#39;m trying to understand the categorical guts underlying zippers. In the Haskell wikibook (and other places) I&#39;ve seen zippers described roughly as the derivatives of functors. However, I haven&#39;t been able to find any references that develop this idea rigorously. For instance, what exactly is the &quot;derivative&quot; of a functor at an object, in the direction of some arrow? I&#39;m interested in studying this concept in more depth, but I can&#39;t find a definition to start with.<br>
<br>Any pointers to good books or papers would be greatly appreciated. :)<br><br>Thank you all-<br><br>Nathan Bloomfield<br>