Re: deductive databases
From: alex goldman <hello_at_spamm.er>
Date: Sat, 14 May 2005 07:27:07 -0700
Message-Id: <1436952.HqgieSMmFo_at_yahoo.com>
>
> It actually depends on what <alex goldman> means by
>
> a. 'Functor', the word that has different meaning in different
> PLs/contexts
>
> b. car(cons(X,Y), X). If it's Lisp, the expression does not make sense.
> If it's a Prolog 'functor', it does not make any sense either.
Date: Sat, 14 May 2005 07:27:07 -0700
Message-Id: <1436952.HqgieSMmFo_at_yahoo.com>
VC wrote:
>
> "Jan Hidders" <jan.hidders_at_REMOVETHIS.pandora.be> wrote in message
> news:xVQge.89347$4x.5404810_at_phobos.telenet-ops.be...
>> alex goldman wrote: >>> While people who responded seem to disagree on whether SQL has >>> recursion, >> >> ?? I didn't see any disagreement. What the different answers told you was >> that this differs per SQL standard and per implementation. >> >>> what about functors? >>> >>> For example, can you express something like this with SQL? >>> >>> for_any X Y : car(cons(X, Y), X) >> >> That depends on what you mean by "can express". Since SQL is a query >> language in which you formulate queries over tables it can only formulate >> queries over tables and not over functors. So in that sense the answer is >> "no" but that observation is about as interesting as the fact that SQL >> also cannot make coffee. If you reformulate it as a statement about >> tables by, for example, modeling car as a binary table and cons as a >> ternary table then you *can* express this and for that you don't even >> need recursion. >> >> -- Jan Hidders
>
> It actually depends on what <alex goldman> means by
>
> a. 'Functor', the word that has different meaning in different
> PLs/contexts
>
> b. car(cons(X,Y), X). If it's Lisp, the expression does not make sense.
> If it's a Prolog 'functor', it does not make any sense either.
In the future, please add qualifiers like "to me" to silly statements like the above. Car of a cons, consisting of X and Y, is X. Received on Sat May 14 2005 - 16:27:07 CEST