X-Git-Url: http://git.scottworley.com/slidingtile/blobdiff_plain/b18667f24728cb960b0c60fa55824062582278bf..e0768fd268b2b06ddd08f24bfc828b397d52a1bb:/sliding_tile_lib.h

diff --git a/sliding_tile_lib.h b/sliding_tile_lib.h
index 89c65c1..4d6c015 100644
--- a/sliding_tile_lib.h
+++ b/sliding_tile_lib.h
@@ -8,7 +8,8 @@ const int BOARD_SIZE = BOARD_DIM * BOARD_DIM;
 
 struct Board {
   signed char board[BOARD_SIZE];
-  bool is_valid();
+  bool is_valid() const;
+  signed char hole() const;
 };
 std::istream& operator>>(std::istream& is, Board& board);