Question

I follow the C family (PHP is a wannabe!) requirement that a statement that spans over multiple lines must be enclosed in curlies.

Scala avoids parse errors in this code from O’Reilly’s Programming Scala.

def apply(specification: String): Option[Widget] = specification match {
    case ButtonExtractorRE(label)   => new Some(new Button(label))
    case TextFieldExtractorRE(text) => new Some(new TextField(text))
    case _ => None
  }

whereas I believe it should look like (the body of the function is enclosed):

def apply(specification: String): Option[Widget] = {
    specification match {
            case ButtonExtractorRE(label)   => new Some(new Button(label))
            case TextFieldExtractorRE(text) => new Some(new TextField(text))
            case _ => None
            }
    }

---

while Scala can parse it, can a programmer “get it”? I dont. Am I missing some intuitive idea?

Should I rather avoid such a practice, if it leads to practical problems (like poor readability?

Answer 1

In Scala much more things (including if, match and for with yield) return a result as in other languages. And more data structures are immutable, which often leads to transformation chains of map, filter, flatMap, collect etc – which also gives just one result. Last but not least Scala has excellent support for tuples, which means that you often get back a tuple as a single result where other languages have to sort out single values.

So in general Scala doesn’t deal as much with variables storing intermediate values as other languages do. That means a function is often just an equation f(a) = b, where b might be quite complex, but is still one chain returning a single result. So it is just naturally to adopt that syntax, which makes immediately clear that you are not juggling with intermediate results, but that you follow a more functional style.

It should be mentioned that functional languages (except the “lispy” family with a quite different syntax) have similar conventions. So if you look at Haskell, F# or Erlang, you usually won’t see any “blocks” for methods. There are structures like let, case and (for Haskell) do which might look a little bit like blocks, but are expressions as well.