Re: Recursive definition in core.logic

[François Rey]

I think this blog post should help: https://kotka.de/blog/2011/10/A_field_trip_into_logic_programming.html The site seems to have an invalid certificate so you may or may not want to proceed, but I just did and all is fine. On 21/09/14 17:07, Casper wrote: I have been looking through core.logic tutorials and while I "get it" I haven't had the big epiphany yet. One thing that keeps nagging me is how to make a relation that isn't "fixed". An example is https://github.com/swannodette/logic-tutorial in which there is defined some relations such as parent, child, son, daughter and granddaughter. As I see it these are all a fixed relationships in that they are a fixed distance from each other. For me that leads to the question, how do we then define the relationship 'descendant' (which would be the generalisation of child, grandchild etc)?  Seems to me that this would involve a recursive definition, but I don't know how to make one like that. Any hints? This is the relevant code from the excellent tutorial made by swannodette, that I linked above: (ns logic-tutorial.tut1   (:refer-clojure :exclude [==])   (:use [clojure.core.logic])   (:use [clojure.core.logic.pldb])) (def rels          (db            [male 'Bob]            [female 'Cindy]            [parent 'John 'Cindy]            [parent 'Jane 'Cindy]            [parent 'John 'Bob]            [parent 'Jane 'Bob])) (defn child [x y]   (parent y x)) (defn son [x y]   (all    (child x y)    (male x))) (defn daughter [x y]   (all    (child x y)    (female x))) (defn grandparent [x y]   (fresh [z]     (parent x z)     (parent z y))) (defn granddaughter [x y]   (fresh [z]     (daughter x z)     (child z y))) ;; Running it (with-db rels     (run* [q]           (child 'Bob q))) -- 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 --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+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 "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 --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.