Scala Gotcha?

There is a weird behavior where the Scala compilers scalac and fsc take argument classpaths that contain shell expansions (such as ~/Documents) in MacOS X but not the Scala REPL scala. The REPL will still execute, but any classpaths with ~ in them will be omitted.

What is the ML Module System?, Part 1

Browsing through the heated Scala mail list discussion from 2009 on OOP versus functional programming, I ran into a number of messages which indicate some confusion as to the role and mechanism of the ML module system. The natural question that was raised is how is a module system different from a "low-level" object system. I am not entirely sure what a "low-level" object system is but in this post I would like to compare and contrast the ML module system and object systems, principally class-based object system but also classless object systems. First, what role do these language features serve? There is some overlap in purpose but also significant differences. The ML module system was originally designed to serve to roles:

1. To support programming-in-the-large organization of large system architecture
2. To facilitate the construction of a type-safe container library

In contrast, OOP is typically defined as supporting design goals of encapsulation, inheritance, and subtype polymorphism. On the surface, this suggests some overlap. Programming-in-the-large may sound like encapsulation, but as I will discuss, the reality is considerably more nuanced.

The Scala Ecosystem

Scala certainly has a lot going for it these days. They have the enthusiasm of at least a couple of the hottest tech companies out there in Twitter and Foursquare. Even Sony is using Scala in some of its systems. There are at least two fairly usable web frameworks, Lift and Play. Akka middleware provides a scalable lock-free concurrency abstraction. XML support is built-in. Interoperability with Java is standard, thus giving Scala access to important systems and APIs such as Hadoop, JSoup, Mahout, Pig, and the numerous Apache Java projects. There is even a linear algebra package Scalala. What is going to take it to the next level?

I've read posts about people recommending Python over Ruby due to the comprehensiveness of the platform given Scipy/Numpy/matplotlib and Django. Ruby, of course, has Rails to really turbocharge its audience. Objective-C remains the lingua franca of iOS due to fiat. The interesting observation is that the software development world has become very diverse. The proliferation of web services certainly helped because instead of having to interface with binary libraries and structured foreign function interfaces, new languages and platforms only have to interface with HTTP, XML, and JSON to achieve harmony with the Web 2.0 ecosystem. This lowers the legacy compatibility bar for new programming languages considerably. Considering how difficult developing good foreign function interfaces and runtime support for mediating between garbage collected (aka managed) languages and the previous lingua franca C was, this must be quite a relief to language designers. However, harmony with Web 2.0 isn't enough to achieve widespread acceptance.

Save bits, save power, save the world, Part 1

Ok, the title was a little tongue-in-cheek. I did a fairly whimsical experiment yesterday. Since text strings are represented as bits which are either 1 (on) or 0 (off), I was wondering which unused domain names used the minimum number of "on" bits. The answer may be non-intuitive to the non-computer scientist.

Firestorm

The past few days have seen a veritable firestorm of flames between the Java and Scala communities. The proximate cause was a leaked private email outlining what the Yammer folks disliked about Scala. An official post from Yammer followed but not before many bloggers had a field day with the leaked email. What is interesting is that one such discussion on Stephen Colebourne's blog pointed that the the lack of a "module system" is a principal deficiency of Scala. This point, mind you, was not part of the Yammer email. In fact, it preceded the email by a few days. The post cited the Scala's community's response to an inquiry about Scala and "module systems" [Google Groups]. That inquiry initially resulted in some misunderstanding.

Scala Performance

I just found this experiment pitting several Python-based servers versus a Scala one. After "priming the pump" to get the VM to optimize the Scala one, Scala handled 3.6x more requests per second than the Python Twisted web server. It even handled 8.5% more requests than a largely C-infused Python server Fast Asyncronous Python WSGI Server. No memory use information was given, but these results do definitely tilt towards Scala.

Interestingly, at least according to the Computer Language Shootout (which admittedly has some issues), Scala significantly outperforms the listed JVM-hosted languages such as JRuby and Clojure (in execution time). JRuby has a steady lead in terms of code size.