从defrel和fact到core.logic.pldb

Question

如果对于 defrel 和事实的弃用以及迁移到 pldb 的方式应该如何更改此代码，我们将不胜感激？

以下代码：

(defrel parent x y)
(facts parent ’[[dave kaylen]
                [frank dave]])

(defn grandparent
    [x y]
    (fresh [z]
        (parent x z)
        (parent z y)))

;; In the REPL
user> (run* [q]
          (fresh [x y]
              (grandparent x y)
              (== q [x y])))
;; Result
([frank kaylen])    

Answer 1

(ns your.ns.here
  (:require [clojure.core.logic.pldb :as pldb]
            [clojure.core.logic :refer :all]))

(pldb/db-rel parent p1 p2)

(def facts
  (pldb/db
    [parent 'dave 'kaylen]
    [parent 'frank 'dave]))

(defn grandparent
  [x y]
  (fresh [z]
         (parent x z)
         (parent z y)))

(pldb/with-db facts
              (doall (run* [q]
                           (fresh [x y]
                                  (grandparent x y)
                                  (== q [x y])))))
=> ([frank kaylen])

有关更多示例，请参阅core.logic源代码中的pldb tests