Hacker News Reader

Comment by yummyfajitas | Hacker News Reader

Why would you ever pattern match on Option[T] in Scala? In all my code, I do either:

    optionalF.map( _.whatever ).getOrElse(fallback)

or perhaps

    (optionalF <+> optionalFallback).getOrElse(finalFallback)

For those unfamiliar with <+>, see here: http://www.chrisstucchio.com/blog/2014/handle_failure_with_p...

View on HN

I think that's a pretty extreme position. First, it will run a lot slower than the pattern matching alternative:

    optional match {
      case Some(x) => whatever(x)
      case None    => fallback
    }

Second, I find the pattern matching code much clearer. Sure, it's also longer, but clarity trumps everything.

map / getOrElse is standard in all the Scala code I've seen. Abstracting over the monad is also a pretty big win that has made some big refactorings painless for me. Pattern matching is really only used by beginners IME.

Well, then maybe the beginners do it right? You have not argued against my two points: It's much slower, and less clear.

Clarity comes from familiarity. It's not an objective measure.

The speed benefit is well known, as is the corollary, premature optimisation. I expect checking for null is even faster if speed is the main concern. It's an engineering tradeoff, just like making the abstraction to a monad (or monad plus). In the normal course of events I'm more concerned about flexibility than performance and would prefer the abstraction.

Reply on news.ycombinator.com