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Better document generate_castle_moves()

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No functional change also in Chess960

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2011-06-30 10:29:58 +02:00
parent 30ca6935a5
commit f3799aa750
1 changed files with 31 additions and 24 deletions
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55
src/movegen.cpp
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@ -501,38 +501,45 @@ namespace {
template<CastlingSide Side>
MoveStack* generate_castle_moves(const Position& pos, MoveStack* mlist, Color us) {
Color them = opposite_color(us);
Square ksq = pos.king_square(us);
CastleRight f = CastleRight((Side == KING_SIDE ? WHITE_OO : WHITE_OOO) << us);
Color them = opposite_color(us);
assert(pos.piece_on(ksq) == make_piece(us, KING));
// After castling, the rook and king's final positions are exactly the same
// in Chess960 as they would be in standard chess.
Square kfrom = pos.king_square(us);
Square rfrom = pos.castle_rook_square(f);
Square kto = relative_square(us, Side == KING_SIDE ? SQ_G1 : SQ_C1);
Square rto = relative_square(us, Side == KING_SIDE ? SQ_F1 : SQ_D1);
Square rsq = pos.castle_rook_square(f);
Square s1 = relative_square(us, Side == KING_SIDE ? SQ_G1 : SQ_C1);
Square s2 = relative_square(us, Side == KING_SIDE ? SQ_F1 : SQ_D1);
Square s;
bool illegal = false;
assert(!pos.in_check());
assert(pos.piece_on(kfrom) == make_piece(us, KING));
assert(pos.piece_on(rfrom) == make_piece(us, ROOK));
assert(pos.piece_on(rsq) == make_piece(us, ROOK));
// 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_empty(s))
// Unimpeded rule: All the squares between the king's initial and final squares
// (including the final square), and all the squares between the rook's initial
// and final squares (including the final square), must be vacant except for
// the king and castling rook.
for (Square s = Min(kfrom, kto); s <= Max(kfrom, kto); s++)
if ( (s != kfrom && s != rfrom && !pos.square_is_empty(s))
||(pos.attackers_to(s) & pos.pieces(them)))
illegal = true;
return mlist;
for (s = Min(rsq, s2); s <= Max(rsq, s2); s++)
if (s != ksq && s != rsq && !pos.square_is_empty(s))
illegal = true;
for (Square s = Min(rfrom, rto); s <= Max(rfrom, rto); s++)
if (s != kfrom && s != rfrom && !pos.square_is_empty(s))
return mlist;
if ( Side == QUEEN_SIDE
&& square_file(rsq) == FILE_B
&& ( pos.piece_on(relative_square(us, SQ_A1)) == make_piece(them, ROOK)
|| pos.piece_on(relative_square(us, SQ_A1)) == make_piece(them, QUEEN)))
illegal = true;
// Because we generate only legal castling moves we need to verify that
// when moving the castling rook we do not discover some hidden checker.
// For instance an enemy queen in SQ_A1 when castling rook is in SQ_B1.
if (pos.is_chess960())
{
Bitboard occ = pos.occupied_squares();
clear_bit(&occ, rfrom);
if (pos.attackers_to(kto, occ) & pos.pieces(them))
return mlist;
}
if (!illegal)
(*mlist++).move = make_castle_move(ksq, rsq);
(*mlist++).move = make_castle_move(kfrom, rfrom);
return mlist;
}