unify_datums.clj

gistfile1.clj

(ns datomic-play.core
  (:use [datomic.api :only [db q] :as d])
  (:require [clojure.core.logic :as l]
            [clojure.pprint :as pp]))

(def uri "datomic:dev://localhost:4334/hello")

(defprotocol IUnifyWithDatum
  (unify-with-datum [u v s]))

(extend-type datomic.db.Datum
  l/IUnifyTerms
  (l/unify-terms [u v s]
    (unify-with-datum v u s)))

(extend-protocol IUnifyWithDatum
  nil
  (unify-with-datum [v u s] false))

(extend-type Object
  IUnifyWithDatum
  (unify-with-datum [v u s] false))

(defn unify-with-datum* [v u s]
  (loop [i 0 v v s s]
    (if (== i 4)
      (if (seq v)
        false
        s)
      (if-let [s (l/unify s (first v) (nth u i))]
        (recur (inc i) (next v) s)
        false))))

(extend-type clojure.lang.Sequential
  IUnifyWithDatum
  (unify-with-datum [v u s]
    (unify-with-datum* v u s)))

(extend-type datomic.db.Datum
  l/IUnifyWithSequential
  (l/unify-with-seq [v u s]
    (unify-with-datum* u v s)))

(comment
  ;; only the first time 
  (d/create-database uri)
  )

(def conn (d/connect uri))

(comment
  (d/transact conn [[:db/add #db/id[:db.part/user] :db/doc "hello world"]])
  (d/transact conn [[:db/add #db/id[:db.part/user] :db/doc "goodbye world"]])
  )

;; with core.logic 0.7.3
(defn datomic-rel [q]
  (fn [a]
    (l/to-stream
      (map #(l/unify a % q) (d/datoms (db conn) :eavt)))))

(comment
  (l/run* [q]
    (l/fresh [e a t]
      (l/== q [e a true t])
      (datomic-rel q)))

  ;; ([39 44 true 13194139533313]
  ;;  [47 51 true 13194139533313]
  ;;  [50 44 true 13194139533313]
  ;;  [61 51 true 13194139533367])
  )