how to create an array with default value in scala?

how to create an array with default value in scala?

I'm working on eclipse under ubuntu 12.04 with scala 2.10 and Akka 2.2.1.
val algorithm = if(args(0) > 1)()=> new A else ()=> new B // A and B
are derived from Node
class work(algorithm: ()=> Node, num: Int){
val a = new Array[Node](num)(algorithm) // here I wanna create an
array with num slots
// and objects of A or B in it
}
I read this post Default value for generic data structure, it does not
work. Eclipse reports
"type mismatch; found: ()=>Node required: Int".
I have no idea how to fix it. Thanks!