Util.Void 

Scalqa/Stream supports a concept of "void object" ("empty object"), which can be defined for any type. This is similar to 'Null Object Pattern'

Unlike 'null', void object can have methods invoked, getting some behavior pertinent to 'voidness'

Examples:

• Void Stream.Interface is a singleton object of empty stream, which can be re-used for any type
• Void Opt, is a singleton optional value with no value, which can be re-used for any type
• Void String, is a string of zero length, which can be re-used for String type instead of null

Void objects have standard way to declare their voidness mixing this trait. Alternatively, Util.Able.Void trait can be mixed and isVoid test added explicitly

Types with void values have to define implicit conversions from Util.Void.Request, aka \/

class Foo

object Foo{
  val Void = new Foo with Void

  implicit def zzMake(v: \/) = Void
}

var v: Foo = \/   // Standard void assignment

A standard way to test for voidness is Util.Void.is method