[ycitm]

The runes are mostly "just because", but there is a reason.

Ideally, I would have written:

  type Nil = unique symbol

Which would ensure the Nil type wouldn't match with anything but itself. Unfortunately, the compiler doesn't allow unique symbol other than on const variables initialised with Symbol(). So I needed some meaningless symbols.

I could also have done

  type Nil = "nil"

But then it would have looked like the string meant something.