Clean up API for attack information

Remove undefined functions sliding_attacks() and ray_attacks()
and retire square_is_attacked(), use the corresponding definition
instead. It is more clear that we are computing full attack
info for the given square.

Alos fix some obsolete comments in move generation functions.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

src/movegen.cpp

@@ -135,7 +135,7 @@ namespace {
 
 
 /// generate_captures generates() all pseudo-legal captures and queen
-/// promotions. The return value is the number of moves generated.
+/// promotions. Returns a pointer to the end of the move list.
 
 MoveStack* generate_captures(const Position& pos, MoveStack* mlist) {
 
@@ -155,7 +155,7 @@ MoveStack* generate_captures(const Position& pos, MoveStack* mlist) {
 
 
 /// generate_noncaptures() generates all pseudo-legal non-captures and
-/// underpromotions. The return value is the number of moves generated.
+/// underpromotions. Returns a pointer to the end of the move list.
 
 MoveStack* generate_noncaptures(const Position& pos, MoveStack* mlist) {
 
@@ -177,7 +177,7 @@ MoveStack* generate_noncaptures(const Position& pos, MoveStack* mlist) {
 
 
 /// generate_non_capture_checks() generates all pseudo-legal non-capturing,
-/// non-promoting checks. It returns the number of generated moves.
+/// non-promoting checks. Returns a pointer to the end of the move list.
 
 MoveStack* generate_non_capture_checks(const Position& pos, MoveStack* mlist, Bitboard dc) {
 
@@ -214,7 +214,7 @@ MoveStack* generate_non_capture_checks(const Position& pos, MoveStack* mlist, Bi
 
 /// generate_evasions() generates all check evasions when the side to move is
 /// in check. Unlike the other move generation functions, this one generates
-/// only legal moves. It returns the number of generated moves.
+/// only legal moves. Returns a pointer to the end of the move list.
 
 MoveStack* generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pinned) {
 
@@ -235,7 +235,7 @@ MoveStack* generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pin
   // Find squares attacked by slider checkers, we will
   // remove them from king evasions set so to avoid a couple
   // of cycles in the slow king evasions legality check loop
-  // and to be able to use square_is_attacked().
+  // and to be able to use attacks_to().
   Bitboard checkers = pos.checkers();
   Bitboard checkersAttacks = EmptyBoardBB;
   Bitboard b = checkers & pos.pieces(BISHOP, QUEEN);
@@ -257,9 +257,9 @@ MoveStack* generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pin
   while (b1)
   {
       to = pop_1st_bit(&b1);
-      // Note that we can use square_is_attacked() only because we
+      // Note that we can use attacks_to() only because we
       // have already removed slider checkers.
-      if (!pos.square_is_attacked(to, them))
+      if (!pos.attacks_to(to, them))
           (*mlist++).move = make_move(ksq, to);
   }
 
@@ -441,7 +441,7 @@ bool move_is_legal(const Position& pos, const Move m, Bitboard pinned) {
       // is occupied or under attack.
       for (s = Min(from, g1); s <= Max(from, g1); s++)
           if (  (s != from && s != to && !pos.square_is_empty(s))
-              || pos.square_is_attacked(s, them))
+              || pos.attacks_to(s, them))
               illegal = true;
 
       // Check if any of the squares between king and rook
@@ -472,7 +472,7 @@ bool move_is_legal(const Position& pos, const Move m, Bitboard pinned) {
 
       for (s = Min(from, c1); s <= Max(from, c1); s++)
           if(  (s != from && s != to && !pos.square_is_empty(s))
-             || pos.square_is_attacked(s, them))
+             || pos.attacks_to(s, them))
               illegal = true;
 
       for (s = Min(to, d1); s <= Max(to, d1); s++)
@@ -942,7 +942,7 @@ namespace {
         // It is a bit complicated to correctly handle Chess960
         for (s = Min(ksq, s1); s <= Max(ksq, s1); s++)
             if (  (s != ksq && s != rsq && pos.square_is_occupied(s))
-                || pos.square_is_attacked(s, them))
+                || pos.attacks_to(s, them))
                 illegal = true;
 
         for (s = Min(rsq, s2); s <= Max(rsq, s2); s++)

src/position.cpp

@@ -510,7 +510,7 @@ bool Position::pl_move_is_legal(Move m, Bitboard pinned) const {
   // If the moving piece is a king, check whether the destination
   // square is attacked by the opponent.
   if (type_of_piece_on(from) == KING)
-      return !(square_is_attacked(move_to(m), opposite_color(us)));
+      return !attacks_to(move_to(m), opposite_color(us));
 
   // A non-king move is legal if and only if it is not pinned or it
   // is moving along the ray towards or away from the king.
@@ -1923,7 +1923,7 @@ bool Position::is_ok(int* failedStep) const {
       Color us = side_to_move();
       Color them = opposite_color(us);
       Square ksq = king_square(them);
-      if (square_is_attacked(ksq, us))
+      if (attacks_to(ksq, us))
           return false;
   }
 

src/position.h

@@ -183,31 +183,26 @@ public:
   Square initial_kr_square(Color c) const;
   Square initial_qr_square(Color c) const;
 
-  // Attack bitboards
-  Bitboard sliding_attacks(Square s, Direction d) const;
-  Bitboard ray_attacks(Square s, SignedDirection d) const;
-  Bitboard pawn_attacks(Color c, Square s) const;
-
-  template<PieceType>
-  Bitboard piece_attacks(Square s) const;
-
   // Bitboards for pinned pieces and discovered check candidates
   Bitboard discovered_check_candidates(Color c) const;
   Bitboard pinned_pieces(Color c, Bitboard& p) const;
   Bitboard pinned_pieces(Color c) const;
 
-  // Checking pieces
+  // Checking pieces and under check information
   Bitboard checkers() const;
+  bool is_check() const;
 
   // Piece lists
   Square piece_list(Color c, PieceType pt, int index) const;
 
   // Attack information for a given square
-  bool square_is_attacked(Square s, Color c) const;
   Bitboard attacks_to(Square s) const;
   Bitboard attacks_to(Square s, Color c) const;
-  bool is_check() const;
   bool pawn_attacks_square(Color c, Square f, Square t) const;
+  Bitboard pawn_attacks(Color c, Square s) const;
+
+  template<PieceType>
+  Bitboard piece_attacks(Square s) const;
 
   template<PieceType>
   Bitboard piece_attacks_square(Square f, Square t) const; // Dispatch at compile-time
@@ -496,11 +491,6 @@ inline Bitboard Position::attacks_to(Square s, Color c) const {
   return attacks_to(s) & pieces_of_color(c);
 }
 
-inline bool Position::square_is_attacked(Square s, Color c) const {
-
-  return attacks_to(s, c) != EmptyBoardBB;
-}
-
 inline bool Position::pawn_is_passed(Color c, Square s) const {
   return !(pieces(PAWN, opposite_color(c)) & passed_pawn_mask(c, s));
 }