On Sep 22, 2012, at 10:52 AM, Eli Barzilay wrote:
> A few minutes ago, Matthias Felleisen wrote: >> >> I consider this problem distinct from Vincent's. > > Yes, the problem is separate (hence moving the discussion) -- it's the > feature that he mentioned (being able to hide types) that I was > referring to. > > >> I'd argue that the separate this/that constructors exist in your >> mind only. > > I'm not following that... If you're saying that the two constructors > are not separate, then I'm more than agreeing -- I'm saying that this > is the main feature of the whole thing: the fact that you cannot treat > them as separate constructors as far as the type system goes. Correct. In ML/standard type terminology, This and That types (I meant types) are VARIANTS not types. It is only in TR's set-oriented type system, that they can play the role of types too. If you wanted to use define-type in plain TR programs (not '311'), you'd want to expose THIS and THAT. _________________________ Racket Developers list: http://lists.racket-lang.org/dev