[jesseschalken]

ADTs can be very easily replaced with visitors.

  type Maybe<T> = <V>(v:{just(x:T):V, nothing():V}) => V
  
  let just = <T>(x:T):Maybe<T> => <V>(v:{just(x:T):V}) => v.just(x)
  let nothing = <T>():Maybe<T> => <V>(v:{nothing():V}) => v.nothing()
  
  let values:Maybe<number>[] = [just(6), nothing()]
  
  values.forEach(maybe => {
    alert(maybe({
      just: x => 'got: ' + x,
      nothing: () => 'nothing'
    }))
  })

[lomnakkus]

Easy, but absolutely horrid on a large scale. (I mean, just try to enumerate the amount of redundancy you have in that short snippet you posted!)