Scala match decomposition on infix operator

Asked 2009-06-20T18:45:05.087

I'm trying to understand the implementation of Lists in Scala. In particular I'm trying to get my head around how you can write match expressions using an infix operator, for example:

a match {
  case Nil => "An empty list"
  case x :: Nil => "A list without a tail"
  case x :: xs => "A list with a tail"
}

How is the match expression allowed to be x :: xs rather than List(x, xs)?

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1 Answer

I believe :: is actually a class (which is a subclass of List), so saying x :: xs is mostly equivalent to List(x, xs).

You can do this with other case classes that have operator names. For instance:

case class %%%(x: Int, y: Int)

a match {
  case x %%% y => x + y
}

answered 2009-06-20T18:52:27.693

Scala match decomposition on infix operator

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