I'm trying to represent a function that takes no arguments and returns no value (I'm simulating the setTimeout function in JavaScript, if you must know.)

case class Scheduled(time : Int, callback :  => Unit)

doesn't compile, saying " `val' parameters may not be call-by-name"

case class Scheduled(time : Int, callback :  () => Unit)  

compiles, but has to be invoked strangely, instead of

Scheduled(40, { println("x") } )

I have to do this

Scheduled(40, { () => println("x") } )      

What also works is

class Scheduled(time : Int, callback :  Unit => Unit)

but is invoked in an even-less-sensible way

 Scheduled(40, { x : Unit => println("x") } )

(What would a variable of type Unit be?) What I want of course is a constructor that can be invoke the way I would invoke it if it were an ordinary function:

 Scheduled(40, println("x") )

Give baby his bottle!