commit 5a74507c79caac7f05e2499d7c51b0d70260ab87
Author: Ray Miller <ray@1729.org.uk>
Date:   Sat Jul 24 12:39:47 2010 +0100

    Initial check-in

diff --git a/.gitignore b/.gitignore
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index 0000000..a02f899
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,5 @@
+pom.xml
+*jar
+lib
+classes*
+*~
diff --git a/README b/README
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index 0000000..6db7e16
--- /dev/null
+++ b/README
@@ -0,0 +1,15 @@
+# ray1729.clojure.sudoku
+
+FIXME: write description
+
+## Usage
+
+FIXME: write
+
+## Installation
+
+FIXME: write
+
+## License
+
+FIXME: write
diff --git a/project.clj b/project.clj
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index 0000000..c7fb8b4
--- /dev/null
+++ b/project.clj
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+(defproject ray1729.clojure.sudoku "1.0.0-SNAPSHOT"
+  :description "FIXME: write"
+  :dependencies [[org.clojure/clojure "1.2.0-master-SNAPSHOT"]
+                 [org.clojure/clojure-contrib "1.2.0-SNAPSHOT"]]
+  :dev-dependencies [[swank-clojure "1.2.1"]])
diff --git a/src/ray1729/clojure/sudoku/core.clj b/src/ray1729/clojure/sudoku/core.clj
new file mode 100644
index 0000000..25f9b5f
--- /dev/null
+++ b/src/ray1729/clojure/sudoku/core.clj
@@ -0,0 +1,91 @@
+(ns ray1729.clojure.sudoku.core
+  (:use [clojure.contrib.string :only (join)])
+  (:require [clojure.contrib.error-kit :as ekit]))
+
+(ekit/deferror *inconsistent-grid* [] []
+  {:msg "Inconsistent grid"
+   :unhandled (ekit/throw-msg Exception)})
+  
+(def rows "ABCDEFGHI")
+(def cols "123456789")
+(def grid-keys (for [r rows c cols] (str r c)))
+(def candidates (apply hash-set "123456789"))
+
+(def empty-grid (apply sorted-map (interleave grid-keys (repeat candidates))))
+
+(defn print-grid [grid]
+  (letfn [(cell->str [cell] (join "" (map #(or (cell %) \.) candidates)))
+	  (row->str  [row]  (join " | " (map #(join " " %) (partition 3 (map cell->str row)))))]
+    (let [rows (map row->str (partition 9 (vals grid)))
+	  separator "------------------------------+-------------------------------+------------------------------"]
+      (doseq [r (apply concat (interpose [separator] (partition 3 rows)))] (println r)))))
+
+(defn row-keys [[r c]] (map #(str r %) cols))
+
+(defn col-keys [[r c]] (map #(str % c) rows))
+
+(defn box-keys [[r c]]
+  (let [row-map (into {} (for [ps (partition 3 rows) e ps] [e ps]))
+	col-map (into {} (for [ps (partition 3 cols) e ps] [e ps]))]
+    (for [row (row-map r) col (col-map c)] (str row col))))
+
+(defn units [s] (vector (row-keys s) (col-keys s) (box-keys s)))
+
+(defn peers [s] (disj (into #{} (apply concat (units s))) s))
+
+(declare assign)
+(declare eliminate)
+
+(defn parse-grid [s]
+  (let [values (filter #(not (= \0 (val %))) (zipmap grid-keys (map first (re-seq #"\d" s))))]
+    (reduce #(assign %1 (key %2) (val %2)) empty-grid values)))
+
+(defn assign [grid cell value]
+  (if ((grid cell) value)
+    (reduce #(eliminate %1 %2 value) (assoc grid cell #{value}) (peers cell))
+    (ekit/raise *inconsistent-grid*)))
+
+(defn eliminate [grid cell value]
+  (if (not ((grid cell) value))
+    grid
+    (let [new-candidates (disj (grid cell) value)
+	  num-candidates (count new-candidates)]
+      (cond
+       (= num-candidates 0) (ekit/raise *inconsistent-grid*)
+       (= num-candidates 1) (assign grid cell (first new-candidates))
+       :else (assoc grid cell new-candidates)))))
+
+(defn solved? [grid]
+  (every? #(= 1 (count %)) (vals grid)))
+
+(defn solve [grid]
+  (if (solved? grid)
+    grid
+    (let [cell (first (filter #(> (count (grid %)) 1) (keys grid)))
+	  candidates (grid cell)
+	  candidate (first candidates)]
+      (ekit/with-handler
+	(do
+	  (println (str "Trying " cell "=" candidate))
+	  (recur (assign grid cell candidate)))
+	(ekit/handle *inconsistent-grid* []		     
+		     (if (next candidates)
+		       (do (println (str "Trying next candidate for " cell))
+			   (recur (eliminate grid cell candidate)))
+		       (ekit/do-not-handle)))))))
+
+(comment
+  
+  (def g1 (parse-grid
+	   "003020600
+            900305001
+            001806400
+            008102900
+            700000008
+            006708200
+            002609500
+            800203009
+            005010300"))
+
+  (def g2 (parse-grid "400000805030000000000700000020000060000080400000010000000603070500200000104000000"))
+  )
\ No newline at end of file
diff --git a/test/ray1729/clojure/sudoku/core_test.clj b/test/ray1729/clojure/sudoku/core_test.clj
new file mode 100644
index 0000000..73f5020
--- /dev/null
+++ b/test/ray1729/clojure/sudoku/core_test.clj
@@ -0,0 +1,6 @@
+(ns ray1729.clojure.sudoku.core-test
+  (:use [ray1729.clojure.sudoku.core] :reload-all)
+  (:use [clojure.test]))
+
+(deftest replace-me ;; FIXME: write
+  (is false))