From 14f47c8ac6a77b9638008a9b61009dd6852be4d6 Mon Sep 17 00:00:00 2001
From: Marco Costalba <mcostalba@gmail.com>
Date: Fri, 30 Aug 2013 07:05:25 +0200
Subject: [PATCH] Use frontmost_sq() and backmost_sq helpers

Should easier to read than the lsb() / msb() low
level functions.

No functional change.
---
 src/bitboard.h  | 9 +++++----
 src/endgame.cpp | 7 ++++---
 src/pawns.cpp   | 4 ++--
 3 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/src/bitboard.h b/src/bitboard.h
index e0e2fe64..3afbeedf 100644
--- a/src/bitboard.h
+++ b/src/bitboard.h
@@ -319,9 +319,10 @@ extern Square pop_lsb(Bitboard* b);
 
 #endif
 
-/// lsb() overload finds least significant bit relative to the given color
-inline Square lsb(Color c, Bitboard b) {
-  return c == WHITE ? lsb(b) : msb(b);
-}
+/// frontmost_sq() and backmost_sq() find the square corresponding to the
+/// most/least advanced bit 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); }
 
 #endif // #ifndef BITBOARD_H_INCLUDED
diff --git a/src/endgame.cpp b/src/endgame.cpp
index 65b85861..9c1c56f1 100644
--- a/src/endgame.cpp
+++ b/src/endgame.cpp
@@ -443,11 +443,12 @@ ScaleFactor Endgame<KBPsK>::operator()(const Position& pos) const {
           // The bishop has the wrong color, and the defending king is on the
           // file of the pawn(s) or the adjacent file. Find the rank of the
           // frontmost pawn.
-          Rank rank = relative_rank(strongerSide, lsb(weakerSide, pawns));
+          Square pawnSq = frontmost_sq(strongerSide, pawns);
+
           // If the defending king has distance 1 to the promotion square or
           // is placed somewhere in front of the pawn, it's a draw.
           if (   square_distance(kingSq, queeningSq) <= 1
-              || relative_rank(strongerSide, kingSq) >= rank)
+              || relative_rank(weakerSide, kingSq) <= relative_rank(weakerSide, pawnSq))
               return SCALE_FACTOR_DRAW;
       }
   }
@@ -459,7 +460,7 @@ ScaleFactor Endgame<KBPsK>::operator()(const Position& pos) const {
       && pos.count<PAWN>(weakerSide) >= 1)
   {
       // Get weakerSide pawn that is closest to home rank
-      Square weakerPawnSq = lsb(weakerSide, pos.pieces(weakerSide, PAWN));
+      Square weakerPawnSq = backmost_sq(weakerSide, pos.pieces(weakerSide, PAWN));
 
       Square strongerKingSq = pos.king_square(strongerSide);
       Square weakerKingSq = pos.king_square(weakerSide);
diff --git a/src/pawns.cpp b/src/pawns.cpp
index fece246b..c5fda172 100644
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -229,11 +229,11 @@ Value Entry::shelter_storm(const Position& pos, Square ksq) {
   for (int f = kf - 1; f <= kf + 1; f++)
   {
       b = ourPawns & FileBB[f];
-      rkUs = b ? relative_rank(Us, lsb(Us, b)) : RANK_1;
+      rkUs = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1;
       safety -= ShelterWeakness[rkUs];
 
       b  = theirPawns & FileBB[f];
-      rkThem = b ? relative_rank(Us, lsb(Us, b)) : RANK_1;
+      rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;
       safety -= StormDanger[rkUs == RANK_1 ? 0 : rkThem == rkUs + 1 ? 2 : 1][rkThem];
   }
 
-- 
2.39.2