Update some comments (#973)

[stockfish] / src / bitboard.h

diff --git a/src/bitboard.h b/src/bitboard.h
index 390966e3494273969bdb53a50c6953a6c9782611..bef6467560bc7efcb122514954686ea5c61b3e93 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) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+  Copyright (C) 2015-2017 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
@@ -124,13 +124,13 @@ inline Bitboard file_bb(Square s) {
 }
 
 
-/// shift_bb() moves a bitboard one step along direction Delta. Mainly for pawns
+/// shift() moves a bitboard one step along direction D. Mainly for pawns
 
-template<Square Delta>
-inline Bitboard shift_bb(Bitboard b) {
-  return  Delta == DELTA_N  ?  b             << 8 : Delta == DELTA_S  ?  b             >> 8
-        : Delta == DELTA_NE ? (b & ~FileHBB) << 9 : Delta == DELTA_SE ? (b & ~FileHBB) >> 7
-        : Delta == DELTA_NW ? (b & ~FileABB) << 7 : Delta == DELTA_SW ? (b & ~FileABB) >> 9
+template<Square D>
+inline Bitboard shift(Bitboard b) {
+  return  D == NORTH      ?  b             << 8 : D == SOUTH      ?  b             >> 8
+        : D == NORTH_EAST ? (b & ~FileHBB) << 9 : D == SOUTH_EAST ? (b & ~FileHBB) >> 7
+        : D == NORTH_WEST ? (b & ~FileABB) << 7 : D == SOUTH_WEST ? (b & ~FileABB) >> 9
         : 0;
 }
 
@@ -164,7 +164,7 @@ inline Bitboard in_front_bb(Color c, Rank r) {
 
 /// forward_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:
-///        ForwardBB[c][s] = in_front_bb(c, s) & file_bb(s)
+///        ForwardBB[c][s] = in_front_bb(c, rank_of(s)) & file_bb(s)
 
 inline Bitboard forward_bb(Color c, Square s) {
   return ForwardBB[c][s];
@@ -174,7 +174,7 @@ inline Bitboard forward_bb(Color c, Square 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:
-///       PawnAttackSpan[c][s] = in_front_bb(c, s) & adjacent_files_bb(s);
+///       PawnAttackSpan[c][s] = in_front_bb(c, rank_of(s)) & adjacent_files_bb(s);
 
 inline Bitboard pawn_attack_span(Color c, Square s) {
   return PawnAttackSpan[c][s];
@@ -291,7 +291,7 @@ inline Square lsb(Bitboard b) {
 
 inline Square msb(Bitboard b) {
   assert(b);
-  return Square(63 - __builtin_clzll(b));
+  return Square(63 ^ __builtin_clzll(b));
 }
 
 #elif defined(_WIN64) && defined(_MSC_VER)