sudoku_compact.clj

gistfile1.clj

;; based on core.logic 0.8-alpha2 or core.logic master branch

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

(defn get-square [rows x y]
  (for [x (range x (+ x 3))
        y (range y (+ y 3))]
    (get-in rows [x y])))

(defn init [vars hints]
  (if (seq vars)
    (let [hint (first hints)]
      (all
        (if-not (zero? hint)
          (== (first vars) hint)
          succeed)
        (init (next vars) (next hints))))
    succeed))

(defn sudokufd [hints]
  (let [vars (repeatedly 81 lvar) 
        rows (->> vars (partition 9) (map vec) (into []))
        cols (apply map vector rows)
        sqs  (for [x (range 0 9 3)
                   y (range 0 9 3)]
               (get-square rows x y))]
    (run 1 [q]
      (== q vars)
      (everyg #(infd % (domain 1 2 3 4 5 6 7 8 9)) vars)
      (init vars hints)
      (everyg distinctfd rows)
      (everyg distinctfd cols)
      (everyg distinctfd sqs))))

;; ====

(comment
  (sudokufd
    [0 0 3  0 2 0  6 0 0
     9 0 0  3 0 5  0 0 1
     0 0 1  8 0 6  4 0 0

     0 0 8  1 0 2  9 0 0
     7 0 0  0 0 0  0 0 8
     0 0 6  7 0 8  2 0 0

     0 0 2  6 0 9  5 0 0
     8 0 0  2 0 3  0 0 9
     0 0 5  0 1 0  3 0 0])
)

It makes good sense.. many thanks! I guess I'll have no other choice than to go through The Reasoned Schemer, to go deeper.

Hey David, where did "infd" go? It's nowhere to be found in the master branch. thx!

@postspectacular - it's in clojure.core.logic.fd now. Here's an updated version that I've been using in my core.logic talks:

https://gist.github.com/orb/5884956

Dead link: http://dosync.posterous.com/friendlier-shorter. Posterous Spaces are no longer available. Has this been republished elsewhere?

https://web.archive.org/web/20130511050728/http://dosync.posterous.com/friendlier-shorter