Inductive Bias

Steps to get a somewhat working Clojure environment with vim:

• Install the current vimclojure plugin.
  
• Get and install a nailgun client.
  
• Add vimclojure to your clojure project pom.xml.
  
• Start the nailgun server from within your maven project with mvn clojure:nailgun with the maven clojure plugin.
  
• Finally start vim, open your favourite clojure file - you can open a REPL with \sr, when in a function definition you can evaluate that with \et - see also tamining vim clojure
  

Note: There is more convenient tooling for emacs (see also getting started with clojure and emacs) - its just that my fingers are more used to interacting with vim...

2nd note: This post is not an introduction or walk through on how to get Clojure setup in vim - it's not even particularly complete. This is intentional - if you want to start tinkering with Clojure: Use Emacs! This is just my way to re-discover through Google what I did the other day but forgot in the mean time.

In today's Clojure meetup Stefan Hübner gave an introduction to Cascalog - a Clojure library based on Cascading for large scale data processing on Apache Hadoop without hassle.

After a brief overview of what he is using the tool for to do log processing at his day job for http://maps.nokia.com Stefan went into some more detail on why he chose Cascalog over other project that provide abstraction layers on top of Hadoop's plain map/reduce library: Both Pig and Hive provide easy to learn SQL-like languages to quickly write analysis jobs. The major disadvantage however comes when in need for domain specific operators - in particular when these turn out to be needed just once: Developers end up switching back and forth between e.g. Pig Latin and Java code to accomplish their analysis need. These kinds of one-off analysis tasks are exactly where Cascalog shines: No need to leave the Clojure context, just program your map/reduce jobs on a very high level (Cascalog itself is quite similar to datalog in syntax which makes it easy to read and simple to forget about all the nitty-gritty details of writing map/reduce jobs).

Writing a join to compute persons' age and gender from a trivial data model is as simple as typing:


;; Persons' age and gender
(? [?person ?age ?gender]
(age ?person ?age)
(gender ?person ?gender)


Multiple sorts of input generators are implemented already: Reading text files, using files in HDFS as input are both common use cases. Of course it is possible to provide your own implementation for that as well to integrate any type of data input in addition to what is available already.

In my view Cascalog combines the speed of development that was brought by Pig and Hive with the flexibility of being able to seemlessly switch to a powerful programming language for anything custom. If you yourself have been using or even contributing to either Cascalog or Cascading: I'd love to see your submission to Berlin Buzzwords - remember, the submission deadline is this week on Sunday *MEZ*.

Though I had the chance to tinker with some Clojure code only briefly it's programming model and the resulting compact programs do fascinate me. As the resulting code runs on a JVM and does integrate well with existing Java libraries migration is comparably cheap and easy.

Today I finally managed to attend the local Berlin Clojure meetup, co-organised by Stefan Hübner and Fronx. Timing couldn't have been much better: In this evenings event Philip Potter from Thoughtworks introduced Overtone - a library for making music with Clojure.

After installing and configuring jack for sound output, supercollider, and overtone outputting your first tone is as simple as registering the overtone library and typing

(definst foo [] (saw 220))
(foo)

To stop it type (stop).

Other types of waves of course are supported as well, so is playing different waves simultaneously and modifying them at runtime. Also expressing sounds as notes (c, d, e, f, g) that may have a certain length is possible of course – which makes it so much easier to design music than having to thing in frequencies.

A sample of what can easily be done with Overtone:


Original sound way better - this sample was taken with a mobile phone, compressed, re-coded and then put online. Checkout Overtone project for the real thing - and don't even try to listen to the sample with low-end laptop speakers ;)

Overall a well organised meetup (Thanks to Soundcloud for hosting it, to the organisers for putting it together and to the speaker for a really well done introduction to Overtone) and an interesting way to get started with Clojure with very fast (audio) feedback.