Singleton ::= Object clone tap {
  self id := 0.
  self newID := {
    self id := self id + 1.
  }.
  self clone := {
    err ArgError clone tap { self message := "Singleton object!". } throw.
  }.
}.

println: Singleton newID. ; 1
println: Singleton newID. ; 2
println: Singleton newID. ; 3