Determine opposite colors mathematically

[stockfish] / src / bitboard.h

diff --git a/src/bitboard.h b/src/bitboard.h
index 4e0267f11e42efbe192224494b2cb69ab6b4dff2..d11b7e732b66227515d83c54647daed57a5937c3 100644 (file)
--- a/src/bitboard.h
+++ b/src/bitboard.h
@@ -2,7 +2,7 @@
   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
   Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
   Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
-  Copyright (C) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+  Copyright (C) 2015-2020 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
 
   Stockfish is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
@@ -119,12 +119,18 @@ inline Bitboard  operator^( Bitboard  b, Square s) { return b ^  square_bb(s); }
 inline Bitboard& operator|=(Bitboard& b, Square s) { return b |= square_bb(s); }
 inline Bitboard& operator^=(Bitboard& b, Square s) { return b ^= square_bb(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, Bitboard b) { return b ^ s; }
+
+inline Bitboard  operator|(Square s, Square s2) { return square_bb(s) | square_bb(s2); }
+
 constexpr bool more_than_one(Bitboard b) {
   return b & (b - 1);
 }
 
-inline bool opposite_colors(Square s1, Square s2) {
-  return bool(DarkSquares & s1) != bool(DarkSquares & s2);
+constexpr bool opposite_colors(Square s1, Square s2) {
+  return (s1 + rank_of(s1) + s2 + rank_of(s2)) & 1;
 }
 
 
@@ -184,8 +190,8 @@ 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.
 
-inline Bitboard adjacent_files_bb(File f) {
-  return shift<EAST>(file_bb(f)) | shift<WEST>(file_bb(f));
+inline Bitboard adjacent_files_bb(Square s) {
+  return shift<EAST>(file_bb(s)) | shift<WEST>(file_bb(s));
 }
 
 
@@ -221,7 +227,7 @@ inline Bitboard forward_file_bb(Color c, Square s) {
 /// starting from the given square.
 
 inline Bitboard pawn_attack_span(Color c, Square s) {
-  return forward_ranks_bb(c, s) & adjacent_files_bb(file_of(s));
+  return forward_ranks_bb(c, s) & adjacent_files_bb(s);
 }
 
 
@@ -229,7 +235,7 @@ inline Bitboard pawn_attack_span(Color c, Square s) {
 /// 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(file_of(s)) | file_bb(s));
+  return forward_ranks_bb(c, s) & (adjacent_files_bb(s) | file_bb(s));
 }
 
 
@@ -376,10 +382,9 @@ inline Square pop_lsb(Bitboard* b) {
 }
 
 
-/// frontmost_sq() and backmost_sq() return the most/least advanced square in
-/// the given bitboard relative to the given color.
-
-inline Square frontmost_sq(Color c, Bitboard b) { return c == WHITE ? msb(b) : lsb(b); }
-inline Square  backmost_sq(Color c, Bitboard b) { return c == WHITE ? lsb(b) : msb(b); }
+/// frontmost_sq() returns the most advanced square for the given color
+inline Square frontmost_sq(Color c, Bitboard b) {
+  return c == WHITE ? msb(b) : lsb(b);
+}
 
 #endif // #ifndef BITBOARD_H_INCLUDED