successors is const

[slidingtile] / sliding_tile_lib.h

diff --git a/sliding_tile_lib.h b/sliding_tile_lib.h
index 300ecdd6de243964e2bd066eec37bdbfa5b060ed..1b56da4c80a7e4fbc18947abc4a6f193c0eb057c 100644 (file)
--- a/sliding_tile_lib.h
+++ b/sliding_tile_lib.h
@@ -22,6 +22,7 @@ struct Board {
   int distance(const InvertedBoard& invo) const;
   bool operator==(const Board& o) const;
   bool operator!=(const Board& o) const;
+  bool operator<(const Board& o) const;
 };
 std::istream& operator>>(std::istream& is, Board& board);
 std::ostream& operator<<(std::ostream& os, const Board& board);
@@ -29,7 +30,7 @@ std::ostream& operator<<(std::ostream& os, const Board& board);
 struct Step {
   Board board;
   std::shared_ptr<Step> prev;
-  std::vector<Step*> successors(std::shared_ptr<Step> shared_this);
+  std::vector<Step*> successors(std::shared_ptr<Step> shared_this) const;
   static signed char adjacent[BOARD_SIZE][5];
 };
 std::ostream& operator<<(std::ostream& os, const Step& step);