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'

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.