How can I create A Class with Trait On Scala? -

trait genericlinkedlist , case class cons , case object nil created below. question want use genericlinkedlist know when write code var list = new genericlinkedlist , not cause traits cannot create object , right? want create class extends genericlinkedlist cannot. how can fix ?

trait genericlinkedlist [+t] { def prepend[tt >: t](x: tt): genericlinkedlist[tt] = match {     case _ => cons(x,this)    } } case class cons[+t](head: t,tail: genericlinkedlist[t]) extends genericlinkedlist[t] case object nil extends genericlinkedlist[nothing] 

your issue seems unable of doing

val list = new genericlinkedlist 

is goal creating empty list?

you can do

val list = new genericlinkedlist[int] { } 

since trait not abstract, it's not pretty. can alternatively define companion object trait

object genericlinkedlist {   def apply[t](): genericlinkedlist[t] = nil } 

and use initialize empty list way

scala> val x = genericlinkedlist[int]() // x: genericlinkedlist[int] = nil  scala> x.prepend(42) // res0: genericlinkedlist[int] = cons(42,nil) 

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by way, universal match in prepend implementation useless. can do

 def prepend[tt >: t](x: tt): genericlinkedlist[tt] = cons(x, this)