condr

condr.clj

(ns numerology.logic.extensions
  (:refer-clojure :exclude [==])
  (:use clojure.core.logic))

;; private function pasted from core.logic
(defn- bind-conde-clause [a]
  (fn [g-rest]
    `(bind* ~a ~@g-rest)))

(defmacro condr
  [& clauses]
  (let [a (gensym "a")]
    `(fn [~a]
       (let [shuffled-clauses# (shuffle [~@(for [clause clauses]
                                             (list 'fn [] ((bind-conde-clause a) clause)))])]
         (-inc
          ((reduce (fn [acc# clause#] (fn [] (mplus (clause#) acc#))) shuffled-clauses#)))))))


(ns numerology.logic.number-play
  (:refer-clojure :exclude [==])
  (:use clojure.core.logic numerology.logic.extensions))

(def nums 1000)
(def num? (set (range nums)))

(defrel +o ^:index x ^:index y ^:index z)
(defrel *o ^:index x ^:index y ^:index z)

(doseq [x (range nums)
        y (range nums)]
  (when (and (num? (+ x y)) (pos? x) (pos? y))
    (fact +o x y (+ x y)))
  (when (and (num? (* x y)) (< 1 x) (< 1 y))
    (fact *o x y (* x y))))

(defn expresso
  [x expr]
  (condr
   ((== expr x))
   ((fresh [a b a' b']
           (condr
            ((+o a b x) (== expr (list '+ a' b')))
            ((+o a x b) (== expr (list '- b' a')))
            ((*o a b x) (== expr (list '* a' b')))
            ((*o a x b) (== expr (list '/ b' a'))))
           (expresso a a')
           (expresso b b')))))

(run 2 [q] (expresso 42 q)) ;; second value is nondeterministic like we want, but first value is consistently 42