1. Clojure: Why is it interesting?
C. Loomis (CNRS/LAL)
Lancement du réseau LoOPS (LAL)
31 mai 2012

2. Contents Facts Interesting Features Use Cases Conclusions
Pan language compiler
StratusLab cloud client
Conclusions
31 May 2012
Clojure (C. Loomis)

3. Clojure Facts It is LISP! And… More info: http://clojure.org/
Functional: but not overly strict about it
Dynamic: supports macros & dynamic compilation
Syntax: (func arg1 arg2) but also with [] and {}
And…
Very active community in US and Europe
Exposes underlying hosting platform!
More info:
31 May 2012
Clojure (C. Loomis)

4. Simple Example (defn cfg-file
"Find the user configuration file to use. The method first
looks in the current working directory, then in the
.stratuslab directory within the user's home directory.
The filename is expected to be stratuslab-user.cfg." []
(first
(filter #(.exists %)
[(io/file (System/getProperty "user.dir")
"stratuslab-user.cfg")
(io/file (System/getProperty "user.home")
".stratuslab"
"stratuslab-user.cfg")])))
31 May 2012
Clojure (C. Loomis)

5. Hosting Environments Java Virtual Machine (JVM)
Excellent interoperability with Java
Uses JVM capabilities and optimizations
ClojureScript  JavaScript (src to src)
Lose dynamic compilation
Gain browser programming
Common Language Runtime (CLR)
Seems to be least used of the three
31 May 2012
Clojure (C. Loomis)

6. Interesting Features Software Transactional Memory
“ACI” but not “D” for databases
Persistent Data Structures
Everything immutable (list, vector, map, set)
Lock-free Concurrency
Atoms, refs, agents, futures, promises
Interoperability with Java
Provides strong set of libraries
31 May 2012
Clojure (C. Loomis)

7. Pan Language Compiler
Part of the Quattor Toolkit (quattor.org) that transforms a site configuration to machine profiles (usually in XML)
Persistent data structures to minimize memory footprint
Concurrency mechanisms for eliminating manual lock management from code base
Memoization for transparent caching
Dynamic compilation to allow user extensions
31 May 2012
Clojure (C. Loomis)

8. StratusLab Cloud Client
All services are REST or XMLRPC services that can easily be accessed from any client
Try external http, xmlrpc, and “ini” file libraries
REPL to provide simple cloud interactive shell
Simple federation of multiple sites
Possible integration with “clojure-control” to act on multiple machine instances simultaneously
Use of “watchers” to simplify interactions with machines
31 May 2012
Clojure (C. Loomis)

9. Conclusions
Simple syntax and powerful abstractions allow for concise implementations
Many promising features for simplifying multithreaded programming
Large and active community working on language and on libraries
Possibility to have a “road show” in Paris region and/or clojure users’ group if there is enough interest
31 May 2012
Clojure (C. Loomis)