canonicalize history representation of moves

baznex · Jul 5, 2012 · ad50c82 · ad50c82
1 parent d61ed4e
commit ad50c82
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Showing 2 changed files with 11 additions and 2 deletions.
diff --git a/src/crosscram/game.clj b/src/crosscram/game.clj
@@ -69,6 +69,12 @@ This will sometimes simply be called a game value.")
            (xor2 (= (Math/abs (long (- r0 r1))) 1)
                  (= (Math/abs (long (- c0 c1))) 1))))))
 
+(defn canonical-domino
+  "Answer a domino such that for all representations D1,D2 of a
+domino, (= (canonical-domino d1) (canonical-domino d2))"
+  [domino]
+  (into [] (sort domino)))
+
 (defn domino-squares
   "Return a sequence of the coordinates occupied by a valid domino."
   [domino]
@@ -190,7 +196,7 @@ for the indicated player. The player ID may be 0 or 1."
   (let [ord (count (:history game))
         board (place-domino (:board game) move ord)]
     (-> game
-        (assoc-in [:history ord] move)
+        (assoc-in [:history ord] (canonical-domino move))
         (assoc :board board))))
 
 (defn rotate-game

diff --git a/test/crosscram/test/game.clj b/test/crosscram/test/game.clj
@@ -26,7 +26,10 @@
   ;; orientation
   (is (horizontal? [[5 9] [5 10]]))
   (is (horizontal? [[5 10] [5 9]]))
-  (is (not (horizontal? [[9 5] [10 5]]))))
+  (is (not (horizontal? [[9 5] [10 5]])))
+  ;; canonical order
+  (is (= (canonical-domino [[0 1] [2 3]])
+         (canonical-domino [[2 3] [0 1]]))))
 
 (deftest boards-and-moves
   (let [empty (make-board [2 3])