gistfile1.nim

type   
  TMaybeKind = enum
    kNone,
    kJust
  TMaybe[T] = object    
    case kind: TMaybeKind     
    of kJust:
      v: ref T 
    else: nil    


proc `$`[T](x: TMaybe[T]): string =
  case x.kind:
  of kNone: result = "None"
  of kJust: result = "Just " & $x.v[]

proc Just[T](x: T): TMaybe[T] =
  result.kind = kJust
  new(result.v)
  result.v[] = x 

proc None(): TMaybe[_] =
   result.kind = kNone

Any thoughts on what to use to instantiate TMaybe[_] as the result of None()? Ideally it would be a "Top" type that would be the super-type of all types. This would allow a None to be universal instead of different for each instantiated type (TMaybe[int], TMaybe[string]), a None should always be None.