Fix compile error with MSVC 2013

[stockfish] / src / position.h

diff --git a/src/position.h b/src/position.h
index 8afbd83e2e9aeb322f9e80aa9a6752183565000e..86acd20d0eb7a174b779147f8e992dce9ff4a7c5 100644 (file)
--- a/src/position.h
+++ b/src/position.h
@@ -22,6 +22,7 @@
 
 #include <cassert>
 #include <cstddef>  // For offsetof()
+#include <string>
 
 #include "bitboard.h"
 #include "types.h"
@@ -174,7 +175,7 @@ public:
   Value non_pawn_material(Color c) const;
 
   // Position consistency check, for debugging
-  bool pos_is_ok(int* step = NULL) const;
+  bool pos_is_ok(int* step = nullptr) const;
   void flip();
 
 private: