My Scala Coding Style

This was originally a posting to the scala-tools mailing list, in response to someone asking how to make the Eclipse plugin format using braces on the next line and spaces instead of tabs.

I used the braces-on-next-line rule, lining up the { to the previous line rule for years, and tabs and no spaces, for years. I was happy with it. I used an 80-character line length limit, which made coding in a text terminal easy, and tabs equivalent to 8 characters (though the actual tab width didn't really matter as I only used indentation to signify nesting depth, not to line up individual characters). My code was very structured.

If you look at my blog's very early days, you will find a post somewhere saying to avoid anonymous classes in Java. This is exactly the opposite of what I'd say now (now I'd say avoid Java :) ). It dawned on me after a while that the reason I didn't like anonymous classes was that my coding style made them a real pain in the backside to use. Specifically, if you have one anonymous class inside another with the above coding style, you end up splitting most lines of actual code.

Then I learned Lisp.

I realised that my overly structured Java code penalised me for nesting. So nesting must be bad, or the coding style must be bad.

Most human languages are highly recursive - within one sentence you can set up phrases, talk about what would happen in the future, and discuss two possible futures or even possible pasts. Only one language is known of that isn't highly recursive - the Piraha language. In Piraha the culture discourages talking about the future, or any event that you haven't seen personally, or been told about by another. A researcher who lived with them and learned their language tried telling them about Jesus (yes, there are God-botherers in linguistics too). One Piraha asked what Jesus looked like - and when the researcher said he didn't know, as Jesus lived 2,000 years ago, the Piraha wasn't interested anymore. This actually caused the researcher to start questioning his own religion, but that's a little beside the point.

I imagine that if you asked a Piraha to design a computer programming language (or a suitable analogy to one - perhaps they wouldn't be interested in computers), I imagine it would be limited to a nesting level of 2, by virtue of a 25-space tab and an 80-character line limit. And if they invented braces, I'm sure they would be lined up.

This has parallels in our society too. The more fluent amongst us can happily deal with long sentences, discussing multiple futures. The less fluent (perhaps speakers of a foreign language learning English) will generally prefer shorter sentences, discussing only the present.

In summary, pick a coding style that doesn't punish nesting, unless you want to make the language 'unnaturally' statement-orientated. I have taken this to an extreme - I use one space for indentation, and never place opening OR closing parens on their own lines. I think this is a direct result of learning Lisp, but it took a long time after learning Lisp for me to change.

Plus, silly Scala makes putting the brace on the next line fail to parse sometimes anyway.