X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fmove.h;h=527699c82f8cf73b6ef9078c06abcf94f0b23ecf;hb=6176357ac18dcc2f0dd12c17d5ac654c86a32009;hp=56659cd983a0fdc93a7b9d40c16e1c1f2c602534;hpb=539051b1e0fb099c0d0da69d20d6a4c2b98a2cb6;p=stockfish

diff --git a/src/move.h b/src/move.h
index 56659cd9..527699c8 100644
--- a/src/move.h
+++ b/src/move.h
@@ -38,10 +38,22 @@
 
 class Position;
 
+/// A move needs 17 bits to be stored
+///
+/// bit  0- 5: destination square (from 0 to 63)
+/// bit  6-11: origin square (from 0 to 63)
+/// bit 12-14: promotion piece type
+/// bit    15: en passant flag
+/// bit    16: castle flag
+///
+/// Special cases are MOVE_NONE and MOVE_NULL. We can sneak these in
+/// because in any normal move destination square is always different
+/// from origin square while MOVE_NONE and MOVE_NULL have the same
+/// origin and destination square, 0 and 1 respectively.
+
 enum Move {
   MOVE_NONE = 0,
-  MOVE_NULL = 65,
-  MOVE_MAX = 0xFFFFFF
+  MOVE_NULL = 65
 };
 
 
@@ -50,17 +62,20 @@ struct MoveStack {
   int score;
 };
 
+// Note that operator< is set up such that std::sort() will sort in descending order
+inline bool operator<(const MoveStack& f, const MoveStack& s) { return s.score < f.score; }
+
 
 ////
 //// Inline functions
 ////
 
 inline Square move_from(Move m) {
-  return Square((int(m) >> 6) & 077);
+  return Square((int(m) >> 6) & 0x3F);
 }
 
 inline Square move_to(Move m) {
-  return Square(m & 077);
+  return Square(m & 0x3F);
 }
 
 inline PieceType move_promotion(Move m) {