Hello Haskell, Goodbye Scala

I spent a fair chunk of my free time last year teaching myself functional programming in Scala. I read Scala For The Impatient and countless other blog posts. I laughed, cried, and managed to learn a great deal.

Earlier this year I decided to ditch Scala for Haskell and get back to some purely functional roots. I thought I’d reflect on my decision a little.

Functional By Convention

Scala is a hybrid language which supports both functional programming and object-oriented programming. It runs on the JVM which means it’s fully interoperable with the amazing wealth of existing Java libraries (for example Apache Commons). It also has an advanced type system, a concise syntax, a robust standard library, and industrial-strength concurrency framework. What’s not to love?

For one Scala is not a purely functional language, which in my view makes it a poor choice for learning functional programming. I’m not saying that it’s a bad language to learn, in fact I think there’s quite a lot to like about it. What I’m saying is that because functional programming in Scala is only a convention (i.e. it’s not enforced by the language) you don’t learn functional programming as quickly as you would with a purely functional language.

Because you aren’t forced to do things the ‘functional way’ it means that if you get stuck solving a problem then you’re likely to fall back on old habits to get the job done. Scala’s flexibility allows you to come at a problem from multiple angles (i.e. imperative and functional), this seems like a good thing™. The problem is that you cheated and didn’t learn anything.

Scalaz

I also spent some time learning about the Scalaz library. It expands your functional tool-belt with a bunch of purely functional data structures.

Scalaz contains a lot of highly academic stuff which I was fairly sure I could live without. There were a few things however, which I was pretty sure I needed to know in order to level-up. For example Functors, Monads, Monoids, and Arrows. But what exactly are these things, why do I need them, and how do I use them? Confusion set in.

If you’re interested in learning about Scalaz there’s a great series of blog posts by Eugene Yokota. There’s also an upcoming book from Paul Chiusano and Rúnar Bjarnason called Functional Programming In Scala which explains some of the theory behind Scalaz.

Searching for answers always lead me back to an explanation in Haskell. It was around this time that I asked myself: why am I bothering to learn Scala/Scalaz when I should just learn Haskell?

Learn Me A Haskell

For christmas I bought myself a copy of Learn You A Haskell For Great Good by Miran Lipovača. Apart from being a great Haskell learning resource, it’s one of the best programming books I have ever read. I’m part-way through my second reading and I feel like I’ve learned more about functional programming in the past six weeks with Haskell than I had in the past six months with Scala.

I don’t regret taking the time to learn Scala, I guess it lowered the bar to grasp some of the functional programming constructs in Haskell. But if could do things differently I would start with Haskell, and then move on to other functional languages.

Bring on the next six months!

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