1. 25

  2. 4

    I disagree with the author. I want something like an object only when I’ll be doing run-time subtyping. Or an open universe, in other words.

    1. 1

      It’s worth noting that “singleton-ness” requires reference equality (you can’t even talk about singletons before you’ve introduced references). So while this might be a good rule of thumb, but strictly less powerful.