Clojure Links To Get You Up To Speed | Hacker News Reader

Clojure Links To Get You Up To Speed

mattsears.com

44 pointsmattsears11 comments

The tutorial by Mark Volkmann is great, and worth reading even if you already program in clojure for a while. There were more then a couple of things I'd skipped on learning in the beginning, or that were introduced after I first read the docs.

I've been looking for something like this for a while. Thanks!

Awesome. This one is definitely getting bookmarked. I'm definitely planning my next project around Clojure, just to learn the language (my current project is in Erlang and mostly because I got the book for it first).

Cool. I just set up a Clojure dev environment.

My questions:

1. can I make the REPL do "up arrow goes back in your command history" like BASH does?

edit: found the answer to this in one of the tutorials

2. Is clojure a good choice for making a screen scraping bot? normally I would use Perl or Ruby for this.

3. Is clojure (or any lisp) a good choice for doing complicated data analysis?

1. most people don't make significant use out of the basic REPL. They use one integrated in to their editor/IDE. Emacs/Slime is probably the most popular, but I think there are addons for the Java IDEs too.

2. That may depend on what you're scraping. Manipulating semi-structured text data is one of Perl's biggest uses, so it may work a bit better than Clojure for the same purpose. Clojure certainly has decent regex and string capabilities though, so yes, it's a good choice.

3. Yes. There's a very good dataflow library for Common Lisp called Cells. It provides dependent and independent variables that work a lot like spreadsheet cells within a program. There's a partial port to Clojure. Also, Clojure has watchers - functions that can be attached to reference types and run whenever their state changes. Clojure and Common Lisp are quite fast at math, especially with type annotations.

I got a sLIME environment set up and found a screen scraping tutorial. It is a regexp based tutorial which seems very Perlish. I guess I was wondering if there was going to be a magical Lisp pattern matching way of doing this. I'm building an aggregator of content for an industry filled with a bunch of jokers who don't have RSS feeds, clean HTML and are bad at keeping things consistent.

Next up, I'm checking out Cells. (that's for a different project than the scraper)

Thanks!

Regarding #2, I believe altlaw.org is exactly such a project. To the best of my knowledge, a screen scraping bot/webapp is the largest clojure project to date.

Thanks for bringing altlaw.org to my attention; lately I've been looking for examples of Clojure being used to do lots of string processing. I've found a presentation of the altlaw project here: http://files.meetup.com/1228907/altlaw-hadoop-meetup-2009-02...

this is great info, much thanks.

There is an excellent Clojure library for screen scraping. It's called Enlive, it's works via CSS3 selectors and thus very powerful and clean:

http://github.com/cgrand/enlive/tree/master

In case anyone is thinking about buying the book: Buy it. It's very good, and it's always nice to have a copy you can leaf through.

Reply on news.ycombinator.com