@Jerzy here's (perhaps an unneeded) clarification just in case it helps: Matthias said initially in a set theoretic type system continuations could be considered as having the empty set as their return _type_ (not value) -- or in other words, their return type would be the empty type, or bottom (which I believe is the "dramatic" something you had suggested). In Typed Racket (U) is bottom (also written 'Nothing' in Typed Racket)).
On Tue, Aug 30, 2016 at 9:10 AM Matthias Felleisen <matth...@ccs.neu.edu> wrote: > > > On Aug 30, 2016, at 3:22 AM, Jerzy Karczmarczuk < > jerzy.karczmarc...@unicaen.fr> wrote: > > > > Could anybody justify this convention? > > > Here the empty set represents the set of all possible result values. > That’s a meta-set or a set about things in the language. > > > An empty set is a legitimate piece of data. > > If you wanted a function to return the empty set as a piece of data, you > would have to choose a set representation. > > In principle, you ought to be able to construct a singleton type that > expresses that a function will return the empty set. > > — Matthias > > -- > You received this message because you are subscribed to the Google Groups > "Racket Users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to racket-users+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
