Why doesn't scala map implement unapply?

Question

I wrote the following usage example in scala:

val wordShortcut = Map("volume" -> "vol", "report" -> "rpt", ...)

object WordShortcutCase {
  def unapply(key: String): Option[String] = wordShortcut.get(key)
}

val pluralR = "(.+)s".r

def encodeToken(token: String) = token match {
  case WordShortcutCase(short) => short
  case pluralR(singular) => singular
  case _ => token
}

if scala Mapwill implement unapply, I don't need an extra object WordShortcutCase(I could use it instead case wordShortcut(short) => short). This seems to me a common model.

And so the question is, why does scala Mapnot implement the method unapply?

Answer 1

Mapdoes not implement unapply, because there is no reasonable implementation that has the same characteristics as other collections.

, , , , apply unapply . , ; , ( "" ):

val xs = List("fish")
val ys = List("fish", "dish")
def iam(zs: List[String]) = zs match {
  case List(x) => println(s"I am a $x")
  case _       => println("Who am I??")
}
iam(xs)  // Prints 'I am a fish'
iam(ys)  // Prints 'Who am I??'

Map , unapply apply, ( , , ). , , , - ; , unapplySeq , , , . .