Scala: First impression

If you are curious enough about programming languages then you probably have heard about Scala - the 'statically typed' functional and object oriented language. Scala is the new sun rising to balance 'the burn factor' between functional and object oriented schools of thoughts.

Unlike what this paper suggests[pdf], The reason why I think Scala exists is because functional v/s object oriented groups are moving in opposite directions, which is not only inefficient but they can't leverage achievements of one another. If you read about functional v/s object oriented programming comparison, every argument boils down to productivity, tooling and maintainability of code. While functional languages (Lisp, Haskell, Python etc.) offer excellent productivity compared to OO languages (Java, C++ etc.), Object oriented languages offer excellent tooling and are relatively maintainable. The reason why I think OO languages have been so popular is due to its easier to understand concept which is easy to map in real life, so for most people who have never took computer science course OO is still easier to grasp compared to Functional programming methods like list comprehension, closures or the higher order functions which are rooted from the formal systems of mathematics.

Scala tries to satisfy both of the groups by providing grammar and a type system which seamlessly integrates with mainstream platforms (Java, .NET) and offers powerful functional abstractions only available in dynamic languages. What this means is, Java developers can write their code in same fashion they write in Java using existing libraries and frameworks but with an added advantage of functional programming techniques wherever they feel it might be productive. Functional programming language enthusiast get access to rich class libraries and powerful tooling (eventually).

If you take a look at the Scala language grammar[pdf] you will notice that what you can create with Scala is limited by your creativity. Based on what I have learned so far, I find Scala much more refreshing than Java, Scala feels a lot more like a programming language of the 21st century! Scala compiler itself is pluggable so you can do heck of a stuff you can only dream with javac, ecj. What is missing is tooling, the existing tooling is scrap but that will improve hopefully with an active community.

Bill Venners of Artima has presented Scala wonderfully, take a look at the presentation[requires flash] on 'The feel of Scala'.

OPath ported for Java object model

I have been thinking about alternate uses of OPath I created for EVars plug-in. And it occurred to me that I can very well use it for my unit testing (which involves pretty complex insurance object model) and for things like JSPs where I really hate to write ten lines of Java code just to display some value.

So I wrote a port of OPath for Java object model (less than 200 lines of real code). Following example should explain how it can add some value to your development efforts:

Consider an example of code for simple Accessible Swing Table :


If you are writing a UI test to see specific table's column heading, you just write following

Collection<Object> findAll = OPathReflectiveInterpreter.findAll(frame, "//dataModel//@val\\$column.*");
assertEquals("First Name",((Object[])findAll.toArray()[0])[0]);

This is very trivial test, of course. But it is sufficient to express the power of OPath micro-scripting.

If you like to try it out for unit-testing or templating check-out the download here (You will also need opath.jar).

Disclaimer: This is experimental work at best, it might be slow and it might have bugs at this time.

EVars Update

Based on the awesome feedback, I have been doing some offline development on EVars plug-in lately. I have added some basic documentation on wiki. Installation is now easy, let P2 do the work to install/update the plug-in (it's a struggle to host update-site with google code).

One of the most exciting feature (Which I can't stop talking about) is value based filtering. Now you can have all the powers of predicate expression, how about searching a map like map//key['@user.*']/.. to select entries matching regular expression user.* ? This update also includes support for relational operators so you can search exactly you want like this //value[count > n] .

I have uploaded OPath grammar for the language enthusiasts (left factored, left recursion free). One feedback was 'experiencing some unresponsive behavior for huge graphs' I have addressed that to some extent by integrating progress monitoring and asynchronous interpretation job.

Thanks for the feedback! Also, for those at EclipseCon have fun with your sessions!

Improve your debugging speed with EVars Eclipse plugin

Update: Added alternate link to screen-cast. Workaround to start plug-in

I have been debugging a lot lately which included open source libraries, closed source web-service engine and parts of closed source application server (WebLogic). During this painful debug-fest I felt a strong need for several features missing in Eclipse (NetBeans as well, for that matter) . Debugging closed applications is a pain beyond imagination, even with IDE integrated decompilers, it takes incredible amount of patience and time to debug.

To improve productivity (or prevent burnout), I jotted down a plugin to export/import live variables, filter variables view with a xpath like expressions etc. The plugin, called 'evars', features a small expression interpreter (similar to xpath) which can do a wonderful job of filtering variables on current stackframe. It also allows you to export variables to a file and reload them at a later point.

For the first time, I have attempted to create a screencast to explain its usefulness. You may watch it over here [10mb non-streaming, 1275x860], alternate link (open with your browser).

I have also created a beta release to see if it finds any interest which you can download it from here [JAR ~800kb, Jdk6] (Click here for Java 5 version) and drop it in dropins folder [Eclipse 3.4+]

If you find it interesting, please leave feedback here.