nested-blocks.md

layout	title	partof	num
overview-large	Nested Blocks	style-guide	5

Curly Braces

Opening curly braces ({) must be on the same line as the declaration they represent:

def foo = {
  ...
}

Technically, Scala's parser does support GNU-style notation with opening braces on the line following the declaration. However, the parser is not terribly predictable when dealing with this style due to the way in which semi-colon inference is implemented. Many headaches will be saved by simply following the curly brace convention demonstrated above.

Parentheses

In the rare cases when parenthetical blocks wrap across lines, the opening and closing parentheses should be unspaced and kept on the same lines as their content (Lisp-style):

(this + is a very ++ long *
  expression)

The only exception to this rule is when defining grammars using parser combinators:

lazy val e: Parser[Int] = (
    e ~ "+" ~ e  ^^ { (e1, _, e2) => e1 + e2 }
  | e ~ "-" ~ e  ^^ { (e1, _, e2) => e1 - e2 }
  | """\d+""".r  ^^ { _.toInt }
)

Parser combinators are an internal DSL, however, meaning that many of these style guidelines are inapplicable.