Re: Proposal: 6NF

Jan Hidders wrote:
> Marshall wrote:
> > On Oct 18, 3:15 pm, "dawn" <dawnwolth..._at_gmail.com> wrote:
> > > A nit, perhaps, but which values would those be that we cannot
> > > represent with computers?
> >
> > I would be hard pressed to figure out how to represent an
> > uncomputable number with a computer. Unless we give it a
> > name like, say, "Fred" and store "Fred" as a string.
> > But then we're representing the name of the value, and
> > not the value itself.
>
> Indeed, the question should not be "which value cannot be represented
> in a computer" (because any value can by just defining a certain symbol
> to mean that value) but "which sets of values cannot be represented in
> a computer". The answer to that is an obvious "any finite or countably
> infinite set". It becomes more interesting if the set you are talking
> about must have certain operations defined over it because then, in
> addition, these operations, including equality, must be computable over
> the chosen representation. For the recursive reals this is possible, [..]

Correction, for the recursive reals this might be problematic since if you choose the algorithm that generates its digits as the representation then equality will be undecidable.

• Jan Hidders