rename shift variables.

Where variable names are explicitly incorrect, I feel morally obligated to at least
suggest an alternative. There are many, but these two are especially egregious.

No functional change.

src/evaluate.cpp

@@ -512,8 +512,6 @@ namespace {
 
     const Color     Them     = (Us == WHITE ? BLACK      : WHITE);
     const Direction Up       = (Us == WHITE ? NORTH      : SOUTH);
-    const Direction Left     = (Us == WHITE ? NORTH_WEST : SOUTH_EAST);
-    const Direction Right    = (Us == WHITE ? NORTH_EAST : SOUTH_WEST);
     const Bitboard  TRank3BB = (Us == WHITE ? Rank3BB    : Rank6BB);
 
     Bitboard b, weak, defended, nonPawnEnemies, stronglyProtected, safeThreats;
@@ -529,7 +527,7 @@ namespace {
         b =  pos.pieces(Us, PAWN)
            & (~attackedBy[Them][ALL_PIECES] | attackedBy[Us][ALL_PIECES]);
 
-        safeThreats = (shift<Right>(b) | shift<Left>(b)) & weak;
+        safeThreats = pos.pawn_attacks<Us>(b) & weak;
         score += ThreatBySafePawn * popcount(safeThreats);
     }
 
@@ -585,7 +583,7 @@ namespace {
         & (attackedBy[Us][ALL_PIECES] | ~attackedBy[Them][ALL_PIECES]);
 
     // Bonus for safe pawn threats on the next move
-    b =  (shift<Left>(b) | shift<Right>(b))
+    b =   pos.pawn_attacks<Us>(b)
        &  pos.pieces(Them)
        & ~attackedBy[Us][PAWN];
 

src/movegen.cpp

@@ -99,8 +99,8 @@ namespace {
     const Bitboard  TRank7BB = (Us == WHITE ? Rank7BB    : Rank2BB);
     const Bitboard  TRank3BB = (Us == WHITE ? Rank3BB    : Rank6BB);
     const Direction Up       = (Us == WHITE ? NORTH      : SOUTH);
-    const Direction Right    = (Us == WHITE ? NORTH_EAST : SOUTH_WEST);
+    const Direction UpRight  = (Us == WHITE ? NORTH_EAST : SOUTH_WEST);
-    const Direction Left     = (Us == WHITE ? NORTH_WEST : SOUTH_EAST);
+    const Direction UpLeft   = (Us == WHITE ? NORTH_WEST : SOUTH_EAST);
 
     Bitboard emptySquares;
 
@@ -168,17 +168,17 @@ namespace {
         if (Type == EVASIONS)
             emptySquares &= target;
 
-        Bitboard b1 = shift<Right>(pawnsOn7) & enemies;
+        Bitboard b1 = shift<UpRight>(pawnsOn7) & enemies;
-        Bitboard b2 = shift<Left >(pawnsOn7) & enemies;
+        Bitboard b2 = shift<UpLeft >(pawnsOn7) & enemies;
         Bitboard b3 = shift<Up     >(pawnsOn7) & emptySquares;
 
         Square ksq = pos.square<KING>(Them);
 
         while (b1)
-            moveList = make_promotions<Type, Right>(moveList, pop_lsb(&b1), ksq);
+            moveList = make_promotions<Type, UpRight>(moveList, pop_lsb(&b1), ksq);
 
         while (b2)
-            moveList = make_promotions<Type, Left >(moveList, pop_lsb(&b2), ksq);
+            moveList = make_promotions<Type, UpLeft >(moveList, pop_lsb(&b2), ksq);
 
         while (b3)
             moveList = make_promotions<Type, Up     >(moveList, pop_lsb(&b3), ksq);
@@ -187,19 +187,19 @@ namespace {
     // Standard and en-passant captures
     if (Type == CAPTURES || Type == EVASIONS || Type == NON_EVASIONS)
     {
-        Bitboard b1 = shift<Right>(pawnsNotOn7) & enemies;
+        Bitboard b1 = shift<UpRight>(pawnsNotOn7) & enemies;
-        Bitboard b2 = shift<Left >(pawnsNotOn7) & enemies;
+        Bitboard b2 = shift<UpLeft >(pawnsNotOn7) & enemies;
 
         while (b1)
         {
             Square to = pop_lsb(&b1);
-            *moveList++ = make_move(to - Right, to);
+            *moveList++ = make_move(to - UpRight, to);
         }
 
         while (b2)
         {
             Square to = pop_lsb(&b2);
-            *moveList++ = make_move(to - Left, to);
+            *moveList++ = make_move(to - UpLeft, to);
         }
 
         if (pos.ep_square() != SQ_NONE)

src/pawns.cpp

@@ -90,8 +90,6 @@ namespace {
 
     const Color     Them  = (Us == WHITE ? BLACK      : WHITE);
     const Direction Up    = (Us == WHITE ? NORTH      : SOUTH);
-    const Direction Right = (Us == WHITE ? NORTH_EAST : SOUTH_WEST);
-    const Direction Left  = (Us == WHITE ? NORTH_WEST : SOUTH_EAST);
 
     Bitboard b, neighbours, stoppers, doubled, supported, phalanx;
     Bitboard lever, leverPush;
@@ -106,7 +104,7 @@ namespace {
     e->passedPawns[Us] = e->pawnAttacksSpan[Us] = e->weakUnopposed[Us] = 0;
     e->semiopenFiles[Us] = 0xFF;
     e->kingSquares[Us]   = SQ_NONE;
-    e->pawnAttacks[Us]   = shift<Right>(ourPawns) | shift<Left>(ourPawns);
+    e->pawnAttacks[Us]   = pos.pawn_attacks<Us>(ourPawns);
     e->pawnsOnSquares[Us][BLACK] = popcount(ourPawns & DarkSquares);
     e->pawnsOnSquares[Us][WHITE] = pos.count<PAWN>(Us) - e->pawnsOnSquares[Us][BLACK];
 

src/position.h

@@ -115,6 +115,7 @@ public:
   Bitboard attacks_from(PieceType pt, Square s) const;
   template<PieceType> Bitboard attacks_from(Square s) const;
   template<PieceType> Bitboard attacks_from(Square s, Color c) const;
+  template<Color> Bitboard pawn_attacks(Bitboard b) const;
   Bitboard slider_blockers(Bitboard sliders, Square s, Bitboard& pinners) const;
 
   // Properties of moves
@@ -288,6 +289,12 @@ inline Bitboard Position::attacks_from(PieceType pt, Square s) const {
   return attacks_bb(pt, s, byTypeBB[ALL_PIECES]);
 }
 
+template<Color c>
+inline Bitboard Position::pawn_attacks(Bitboard b) const {
+  return c == WHITE ? shift<NORTH_WEST>(b) | shift<NORTH_EAST>(b)
+                    : shift<SOUTH_WEST>(b) | shift<SOUTH_EAST>(b);
+}
+
 inline Bitboard Position::attackers_to(Square s) const {
   return attackers_to(s, byTypeBB[ALL_PIECES]);
 }