Why did you decide "against" using Erlang?

Question

I returned to Haskell for my personal projects from Erlang for the simple virtue of Haskell's amazing type system. Erlang gives you a ton of tools to handle when things go wrong. Haskell gives you tools to keep you from going wrong in the first place.

When working in a language with a strong type system you are effectively proving free theorems about your code every time you compile.

You also get a bunch of overloading sugar from Haskell's typeclass machinery, but that is largely secondary to me -- even if it does allow me to express a number of abstractions that would be terribly verbose or non-idiomatic and unusable in Erlang (e.g. Haskell's category-extras).

I love Erlang, I love its channels and its effortless scalability. I turn to it when these are the things I need. Haskell isn't a panacea. I give up a better operational understanding of space consumption. I give up the magical one pass garbage collector. I give up OTP patterns and all that effortless scalability.

But its hard for me to give up the security blanket that, as is commonly said, in Haskell, if it typechecks, it is probably correct.

We use Haskell, OCaml and (now) F# so for us it has nothing to do with lack of C-like syntax. Rather we skip Erlang because:

• It's dynamically typed (we're fans of Haskell's type system)
• Doesn't provide a 'real' string type (I understand why, but it's annoying that this hasn't been corrected at the language level yet)
• Tends to have poor (incomplete or unmaintained) database drivers
• It isn't batteries included and doesn't appear to have a community working on correcting this. If it does, it isn't highly visible. Haskell at least has Hackage, and I'd guess that's what has us choosing that language over any other. In Windows environments F# is about to have the ultimate advantage here.

There are probably other reasons I can't think of right now, but these are the major points.

The best reason to avoid Erlang is when you cannot commit to the functional way of programming.

I read an anti-Erlang blog rant a few weeks ago, and one of the author's criticisms of Erlang is that he couldn't figure out how to make a function return a different value each time he called it with the same arguments. What he really hadn't figured out is that Erlang is that way on purpose. That's how Erlang manages to run so well on multiple processors without explicit locking. Purely functional programming is side-effect-free programming. You can arm-twist Erlang into working like our ranting blogger wanted, adding side effects, but in doing so you throw away the value Erlang offers.

Pure functional programming is not the only right way to program. Not everything needs to be mathematically rigorous. If you determine your application would be best written in a language that misuses the term "function", better cross Erlang off your list.

I have used Erlang in a few project already. I often use it for restful services. Where I don't use it however is for complex front end web applications where tools like Ruby on Rails are far better. But for the powerbroker behind the scenes I know of no better tool than Erlang.

I also use a few applications written in Erlang. I use CouchDB and RabbitMQ a bit and I have set up a few EJabberd servers. These applications are the most powerful, easiest and flexible tools in their field.

Not wanting to use Erlang because it does not use JVM is in my mind pretty silly. JVM is not some magical tool that is the best in doing everything in the world. In my mind the ability to choose from an arsenal of different tools and not being stuck in a single language or framework is what separates experts from code monkeys.

PS: After reading my comment back in context I noticed it looked like I was calling oxbow_lakes a code monkey. I really wasn't and apologize if he took it like that. I was generalizing about types of programmers and I would never call an individual such a negative name based on one comment by him. He is probably a good programmer even though I encourage him to not make the JVM some sort of a deal breaker.

Whilst I haven't, others on the internet have, e.g.

We investigated the relative merits of C++ and Erlang in the implementation of a parallel acoustic ray tracing algorithm for the U.S. Navy. We found a much smaller learning curve and better debugging environment for parallel Erlang than for pthreads-based C++ programming. Our C++ implementation outperformed the Erlang program by at least 12x. Attempts to use Erlang on the IBM Cell BE microprocessor were frustrated by Erlang's memory footprint. (Source)

And something closer to my heart, which I remember reading back in the aftermath of the ICFP contest:

The coding was very straightforward, translating pseudocode into C++. I could have used Java or C#, but I'm at the point where programming at a high level in C++ is just as easy, and I wanted to retain the option of quickly dropping down into some low-level bit-twiddling if it came down to it. Erlang is my other favorite language for hacking around in, but was worried about running into some performance problem that I couldn't extricate myself from. (Source)

For me, the fact that Erlang is dynamically typed is something that makes me wary. Although I do use dynamically typed languages because some of them are just so very problem-oriented (take Python, I solve a lot of problems with it), I wish they were statically typed instead.

That said, I actually intended to give Erlang a try for some time, and I’ve just started downloading the source. So your “question” achieved something after all. ;-)

I know Erlang since university, but have never used it in my own projects so far. Mainly because I'm mostly developing desktop applications, and Erlang is not a good language for making nice GUIs. But I will soon implement a server application, and I will give Erlang a try, because that's what it's good for. But I'm worring that I need more librarys, so maybe I'll try with Java instead.