[Haskell-cafe] mapping a concept to a type

[Edward Z. Yang]

> I find both heavy and redundant. The first forces me to specify if I want
> an argument of not (with the constructors MR and NR)

I'm sorry, I don't understand what you mean here.

> Do you know of a construction/abstraction that allows having or not an
> argument (a variable number of arguments, here zero or one)?

Either way you do it (Maybe, or building the variant yourself), you're
going to need a constructor. This is a feature, not a bug.

Edward