Several commenters pointed out that I made several mistakes in my description of Erlang. It turns out that the main reference source I used for this post, an excerpt from a textbook on Erlang available on the Erlang website, is quite out of date. I didn’t realize this; I assumed that if they pointed towards that as a tutorial, that it would represent the current state of the language. My bad. As a result, several things that I said about Erlang – including some negative comments, were inaccurate. I’ve updated the article, and the changes are marked with comments.
As long-time readers will recall, one of my greatest interests in programming languages. A while back, I wrote a tutorial on Haskell, which is one of the most influential languages currently in the programming language research community. Haskell is a pure, lazy, functional language which gained a lot of attention in recent times for being incredibly expressive, while maintaining a solid theoretical basis with well-defined semantics. What made Haskell unusual was that it’s a completely pure functional language – meaning no true state at all – not for I/O, not for assignment, not for mutable data – but through the
use of a clever construct called a monad, you can create the effect of state without disturbing the functional semantics of the language. It’s quite a nice idea, although I must admit that I remain somewhat skeptical about how scaleable it might be.
One of the competitors of Haskell for mindshare in the community of people who are interested in functional programming languages is a language called Erlang. In many ways, Erlang is a polar opposite to Haskell. Erlang is, basically, a functional language, but it’s designers didn’t object to tossing in a bit of state when it made things easier. It’s dynamically typed,
and even for a dynamically typed language, it’s support for typing is weak. It’s gotten its attention for a couple of big reasons:
- Erlang was designed by Ericsson for implementing the software in their switches and routers. It’s the first functional language designed by a company for building production applications for extremely complex performance-critical low-level applications like switching and routing.
- Erlang is specifically designed for building distributed systems. As I’ve mentioned before, programming for distributed systems is incredibly difficult, and most programming languages are terrible at it.
Concurrency and distributed systems are a big deal. I’d argue that programming for concurrency and distribution are the biggest problems facing software developers today. Pretty much every computer that you can buy has multiple processors, and to take full advantage of their power, code needs to use concurrency. And the network is an unavoidable part of our environment: many of the applications that we’re writing today need to be aware of the internet, and need to interact with other systems. These are just simple facts of the modern computing world – and software developers need tools to deal with them.
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