196 

   196 // guards in pattern-matching

   197 

   197 

   198 def foo(xs: List[Int]) : String = xs match {

   199   case Nil => s"this list is empty"

   200   case x :: xs if x % 2 == 0

   201      => s"the first elemnt is even"

   202   case x :: y :: rest if x == y

   203      => s"this has two elemnts that are the same"

   204   case hd :: tl => s"this list is standard $hd::$tl"

   205 }

   206 

   207 foo(Nil)

   208 foo(List(1,2,3))

   209 foo(List(1,2))

   210 foo(List(1,1,2,3))

   211 foo(List(2,2,2,3))