Clojure Zippers (2021)(grishaev.me)

111 pointsby prydt9 bulan yang lalu7 comments

Clojure Zippers (2021)

https://grishaev.me/en/clojure-zippers/

8 comments

I've used zippers a couple times.

Once for navigating a collection of deeply nested routes in a webapp, and once for navigating deeply nested xml to grab very particular data.

Both times it was pretty pleasant and nice to use.

I wouldn't reach for them in most normal situations cause they're more complicated to get right than simple looping (or `clojure.walk/prewalk`), but if you have large semi-predictable data structures, you can do cool stuff with zippers.

0_gravitas9 bulan yang lalu

I've been using Clojure for a few years now and zippers have always been a blindspot (had no idea even _when_ they would be useful), this is a remarkable tutorial!

ngruhn9 bulan yang lalu

I'm not sure if I get it. But I don't know Clojure syntax too well. Say I want to represent a slideshow state. I could do it with

    { 
      slides: List<Slide>, 
      current_index: Int
    }

Or alternatively:

    {
      left_slides: List<Slide>,
      current: Slide,
      right_slides: List<Slide>
    }

Is it fair to call the latter a Zipper?

shakadak9 bulan yang lalu

Yes, although it's usually defined as:

    {
      slides_shown: List<Slide>,
      slides_left: List<Slide>
    }

Where the head of slides_left is the current slide. Pretty much any recursive data structure can be derived into a zipper.

laszlokorte9 bulan yang lalu

Yes if List is immutable and the interface for stepping through the slides ist designed accordingly

clem9 bulan yang lalu

I've used zippers to edit parse trees. Very useful API, if a little user unfriendly.

avbanks9 bulan yang lalu

This tutorial was extremely helpful, I was having a hard time grokking the power of zippers.

CNNCultists9 bulan yang lalu