X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fbitboard.h;h=afeb40ec146f2af01d2626111fe19450148c90f3;hp=704f4bb4e8a463d3d349bfee9fefcbbf9df63bc6;hb=4006f2c9132db034a27a94be33070d6aaab75b24;hpb=b0eb5a1ba3d094a1d2236db6f33e0d2164ec3480

diff --git a/src/bitboard.h b/src/bitboard.h
index 704f4bb4..afeb40ec 100644
--- a/src/bitboard.h
+++ b/src/bitboard.h
@@ -110,6 +110,7 @@ inline Bitboard square_bb(Square s) {
   return SquareBB[s];
 }
 
+
 /// Overloads of bitwise operators between a Bitboard and a Square for testing
 /// whether a given bit is set in a bitboard, and for setting and clearing bits.
 
@@ -123,7 +124,7 @@ inline Bitboard  operator&(Square s, Bitboard b) { return b & s; }
 inline Bitboard  operator|(Square s, Bitboard b) { return b | s; }
 inline Bitboard  operator^(Square s, Bitboard b) { return b ^ s; }
 
-inline Bitboard  operator|(Square s, Square s2) { return square_bb(s) | s2; }
+inline Bitboard  operator|(Square s1, Square s2) { return square_bb(s1) | s2; }
 
 constexpr bool more_than_one(Bitboard b) {
   return b & (b - 1);
@@ -137,19 +138,19 @@ constexpr bool opposite_colors(Square s1, Square s2) {
 /// rank_bb() and file_bb() return a bitboard representing all the squares on
 /// the given file or rank.
 
-inline Bitboard rank_bb(Rank r) {
+constexpr Bitboard rank_bb(Rank r) {
   return Rank1BB << (8 * r);
 }
 
-inline Bitboard rank_bb(Square s) {
+constexpr Bitboard rank_bb(Square s) {
   return rank_bb(rank_of(s));
 }
 
-inline Bitboard file_bb(File f) {
+constexpr Bitboard file_bb(File f) {
   return FileABB << f;
 }
 
-inline Bitboard file_bb(Square s) {
+constexpr Bitboard file_bb(Square s) {
   return file_bb(file_of(s));
 }
 
@@ -194,16 +195,17 @@ constexpr Bitboard pawn_double_attacks_bb(Bitboard b) {
 
 
 /// adjacent_files_bb() returns a bitboard representing all the squares on the
-/// adjacent files of the given one.
+/// adjacent files of a given square.
 
-inline Bitboard adjacent_files_bb(Square s) {
+constexpr Bitboard adjacent_files_bb(Square s) {
   return shift<EAST>(file_bb(s)) | shift<WEST>(file_bb(s));
 }
 
-/// line_bb(Square, Square) returns a Bitboard representing an entire line
-/// (from board edge to board edge) that intersects the given squares.
-/// If the given squares are not on a same file/rank/diagonal, return 0.
-/// Ex. line_bb(SQ_C4, SQ_F7) returns a bitboard with the A2-G8 diagonal.
+
+/// line_bb() returns a bitboard representing an entire line (from board edge
+/// to board edge) that intersects the two given squares. If the given squares
+/// are not on a same file/rank/diagonal, the function returns 0. For instance,
+/// line_bb(SQ_C4, SQ_F7) will return a bitboard with the A2-G8 diagonal.
 
 inline Bitboard line_bb(Square s1, Square s2) {
 
@@ -211,10 +213,11 @@ inline Bitboard line_bb(Square s1, Square s2) {
   return LineBB[s1][s2];
 }
 
-/// between_bb() returns a Bitboard representing squares that are linearly
-/// between the given squares (excluding the given squares).
-/// If the given squares are not on a same file/rank/diagonal, return 0.
-/// Ex. between_bb(SQ_C4, SQ_F7) returns a bitboard with squares D5 and E6.
+
+/// between_bb() returns a bitboard representing squares that are linearly
+/// between the two given squares (excluding the given squares). If the given
+/// squares are not on a same file/rank/diagonal, we return 0. For instance,
+/// between_bb(SQ_C4, SQ_F7) will return a bitboard with squares D5 and E6.
 
 inline Bitboard between_bb(Square s1, Square s2) {
   Bitboard b = line_bb(s1, s2) & ((AllSquares << s1) ^ (AllSquares << s2));
@@ -226,7 +229,7 @@ inline Bitboard between_bb(Square s1, Square s2) {
 /// in front of the given one, from the point of view of the given color. For instance,
 /// forward_ranks_bb(BLACK, SQ_D3) will return the 16 squares on ranks 1 and 2.
 
-inline Bitboard forward_ranks_bb(Color c, Square s) {
+constexpr Bitboard forward_ranks_bb(Color c, Square s) {
   return c == WHITE ? ~Rank1BB << 8 * relative_rank(WHITE, s)
                     : ~Rank8BB >> 8 * relative_rank(BLACK, s);
 }
@@ -235,16 +238,16 @@ inline Bitboard forward_ranks_bb(Color c, Square s) {
 /// forward_file_bb() returns a bitboard representing all the squares along the
 /// line in front of the given one, from the point of view of the given color.
 
-inline Bitboard forward_file_bb(Color c, Square s) {
+constexpr Bitboard forward_file_bb(Color c, Square s) {
   return forward_ranks_bb(c, s) & file_bb(s);
 }
 
 
 /// pawn_attack_span() returns a bitboard representing all the squares that can
-/// be attacked by a pawn of the given color when it moves along its file,
-/// starting from the given square.
+/// be attacked by a pawn of the given color when it moves along its file, starting
+/// from the given square.
 
-inline Bitboard pawn_attack_span(Color c, Square s) {
+constexpr Bitboard pawn_attack_span(Color c, Square s) {
   return forward_ranks_bb(c, s) & adjacent_files_bb(s);
 }
 
@@ -252,8 +255,8 @@ inline Bitboard pawn_attack_span(Color c, Square s) {
 /// passed_pawn_span() returns a bitboard which can be used to test if a pawn of
 /// the given color and on the given square is a passed pawn.
 
-inline Bitboard passed_pawn_span(Color c, Square s) {
-  return forward_ranks_bb(c, s) & (adjacent_files_bb(s) | file_bb(s));
+constexpr Bitboard passed_pawn_span(Color c, Square s) {
+  return pawn_attack_span(c, s) | forward_file_bb(c, s);
 }
 
 
@@ -276,7 +279,9 @@ template<> inline int distance<Square>(Square x, Square y) { return SquareDistan
 inline int edge_distance(File f) { return std::min(f, File(FILE_H - f)); }
 inline int edge_distance(Rank r) { return std::min(r, Rank(RANK_8 - r)); }
 
-/// Return the target square bitboard if we do not step off the board, empty otherwise
+
+/// safe_destination() returns the bitboard of target square for the given step
+/// from the given square. If the step is off the board, returns empty bitboard.
 
 inline Bitboard safe_destination(Square s, int step)
 {
@@ -284,6 +289,7 @@ inline Bitboard safe_destination(Square s, int step)
     return is_ok(to) && distance(s, to) <= 2 ? square_bb(to) : Bitboard(0);
 }
 
+
 /// attacks_bb(Square) returns the pseudo attacks of the give piece type
 /// assuming an empty board.
 
@@ -295,6 +301,7 @@ inline Bitboard attacks_bb(Square s) {
   return PseudoAttacks[Pt][s];
 }
 
+
 /// attacks_bb(Square, Bitboard) returns the attacks by the given piece
 /// assuming the board is occupied according to the passed Bitboard.
 /// Sliding piece attacks do not continue passed an occupied square.