[Haskell-cafe] looking for examples of non-full Functional Dependencies

[Tom Schrijvers]

On Fri, 25 Apr 2008, Hans Aberg wrote:

> On 25 Apr 2008, at 14:20, Tom Schrijvers wrote:
>
>> Prolog works under the assumption of a closed world. That's contrary to the 
>> open world view of regular type classes. So these aren't the intended 
>> semantics.
>
> By which I gather you mean the interpretation of ":-" as logical connective 
> "=>" rather than provability "|-"?

What I meant was that when Prolog says "there are no more solutions", it 
doesn't know of any more. In realtiy it means "there no more 
solutions under the closed world assumption". That means there could be 
more solutions if you haven't told Prolog everything. In this context, 
there may be more class instances (you simply haven't told the system 
yet).

> My point, though, was to interpret
> class a b | a -> b
> as a functional dependency b = b(a) rather than as
> D a b, D a c ==> b=c
> Thus trying to eliminate the use of "=".

I don't follow you here.

Tom

--
Tom Schrijvers

Department of Computer Science
K.U. Leuven
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tel: +32 16 327544
e-mail: tom.schrijvers at cs.kuleuven.be
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