Thanks a lot David. As much as I'd like to contribute, I've only just started looking into logic programming.
Stathis On Wednesday, 19 September 2012 17:42:09 UTC+1, David Nolen wrote: > > On Wed, Sep 19, 2012 at 11:11 AM, Stathis Sideris > <sid...@gmail.com<javascript:>> > wrote: > > Hello, > > > > Is there a way to negate a goal in core.logic? I have written this goal > > below, and I would like to use it to query all the pairs of people who > are > > *not* relatives according to my facts (for dating purposes of course :-D) > > > > (defn relative [p1 p2] > > (conde > > [(parent p1 p2)] > > [(parent p2 p1)] > > [(sibling p1 p2)] > > [(cousin p1 p2)] > > [(nephew p1 p2)] > > [(uncle p1 p2)])) > > > > > > Thanks, > > > > Stathis > > core.logic currently only supports Prolog's negation as failure. You can > write a goal that looks like this: > > (defn not [g] > (fn [a] > (if (nil? (g a)) > a))) > > But you must be careful if you use this, all logic vars passed to the goal > g must be ground. So it's not relational. > > I have some leads based on recent Prolog research (CiaoProlog, and an > interesting dissertation on the abstract interpretation of Prolog) for > really handling negation in core.logic but I don't think I'll have time to > deal with it any time soon. Again, more than willing and excited to > collaborate with people who would like to see it done sooner. > > David > -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
