2 * moves.c - Move generation and checking
4 * Copyright 1991 by Digital Equipment Corporation, Maynard,
7 * Enhancements Copyright 1992-2001, 2002, 2003, 2004, 2005, 2006,
8 * 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
10 * Enhancements Copyright 2005 Alessandro Scotti
12 * The following terms apply to Digital Equipment Corporation's copyright
14 * ------------------------------------------------------------------------
17 * Permission to use, copy, modify, and distribute this software and its
18 * documentation for any purpose and without fee is hereby granted,
19 * provided that the above copyright notice appear in all copies and that
20 * both that copyright notice and this permission notice appear in
21 * supporting documentation, and that the name of Digital not be
22 * used in advertising or publicity pertaining to distribution of the
23 * software without specific, written prior permission.
25 * DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
26 * ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
27 * DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
28 * ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
29 * WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
30 * ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
32 * ------------------------------------------------------------------------
34 * The following terms apply to the enhanced version of XBoard
35 * distributed by the Free Software Foundation:
36 * ------------------------------------------------------------------------
38 * GNU XBoard is free software: you can redistribute it and/or modify
39 * it under the terms of the GNU General Public License as published by
40 * the Free Software Foundation, either version 3 of the License, or (at
41 * your option) any later version.
43 * GNU XBoard is distributed in the hope that it will be useful, but
44 * WITHOUT ANY WARRANTY; without even the implied warranty of
45 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
46 * General Public License for more details.
48 * You should have received a copy of the GNU General Public License
49 * along with this program. If not, see http://www.gnu.org/licenses/. *
51 *------------------------------------------------------------------------
52 ** See the file ChangeLog for a revision history. */
59 #else /* not HAVE_STRING_H */
61 #endif /* not HAVE_STRING_H */
67 int WhitePiece P((ChessSquare));
68 int BlackPiece P((ChessSquare));
69 int SameColor P((ChessSquare, ChessSquare));
70 int PosFlags(int index);
72 extern signed char initialRights[BOARD_FILES]; /* [HGM] all rights enabled, set in InitPosition */
78 return (int) piece >= (int) WhitePawn && (int) piece < (int) BlackPawn;
84 return (int) piece >= (int) BlackPawn && (int) piece < (int) EmptySquare;
87 int SameColor(piece1, piece2)
88 ChessSquare piece1, piece2;
90 return ((int) piece1 >= (int) WhitePawn && /* [HGM] can be > King ! */
91 (int) piece1 < (int) BlackPawn &&
92 (int) piece2 >= (int) WhitePawn &&
93 (int) piece2 < (int) BlackPawn)
94 || ((int) piece1 >= (int) BlackPawn &&
95 (int) piece1 < (int) EmptySquare &&
96 (int) piece2 >= (int) BlackPawn &&
97 (int) piece2 < (int) EmptySquare);
100 char pieceToChar[] = {
101 'P', 'N', 'B', 'R', 'Q', 'F', 'E', 'A', 'C', 'W', 'M',
102 'O', 'H', 'I', 'J', 'G', 'D', 'V', 'L', 'S', 'U', 'K',
103 'p', 'n', 'b', 'r', 'q', 'f', 'e', 'a', 'c', 'w', 'm',
104 'o', 'h', 'i', 'j', 'g', 'd', 'v', 'l', 's', 'u', 'k',
106 char pieceNickName[EmptySquare];
111 if((int)p < 0 || (int)p >= (int)EmptySquare) return('x'); /* [HGM] for safety */
112 return pieceToChar[(int) p];
115 int PieceToNumber(p) /* [HGM] holdings: count piece type, ignoring non-participating piece types */
119 ChessSquare start = (int)p >= (int)BlackPawn ? BlackPawn : WhitePawn;
121 while(start++ != p) if(pieceToChar[(int)start-1] != '.') i++;
125 ChessSquare CharToPiece(c)
129 for(i=0; i< (int) EmptySquare; i++)
130 if(pieceNickName[i] == c) return (ChessSquare) i;
131 for(i=0; i< (int) EmptySquare; i++)
132 if(pieceToChar[i] == c) return (ChessSquare) i;
136 void CopyBoard(to, from)
141 for (i = 0; i < BOARD_HEIGHT; i++)
142 for (j = 0; j < BOARD_WIDTH; j++)
143 to[i][j] = from[i][j];
144 for (j = 0; j < BOARD_FILES-1; j++) // [HGM] gamestate: copy castling rights and ep status
145 to[CASTLING][j] = from[CASTLING][j];
146 to[HOLDINGS_SET] = 0; // flag used in ICS play
149 int CompareBoards(board1, board2)
150 Board board1, board2;
154 for (i = 0; i < BOARD_HEIGHT; i++)
155 for (j = 0; j < BOARD_WIDTH; j++) {
156 if (board1[i][j] != board2[i][j])
163 /* Call callback once for each pseudo-legal move in the given
164 position, except castling moves. A move is pseudo-legal if it is
165 legal, or if it would be legal except that it leaves the king in
166 check. In the arguments, epfile is EP_NONE if the previous move
167 was not a double pawn push, or the file 0..7 if it was, or
168 EP_UNKNOWN if we don't know and want to allow all e.p. captures.
169 Promotion moves generated are to Queen only.
171 void GenPseudoLegal(board, flags, callback, closure)
174 MoveCallback callback;
178 int i, j, d, s, fs, rs, rt, ft, m;
179 int epfile = (signed char)board[EP_STATUS]; // [HGM] gamestate: extract ep status from board
180 int promoRank = gameInfo.variant == VariantMakruk ? 3 : 1;
182 for (rf = 0; rf < BOARD_HEIGHT; rf++)
183 for (ff = BOARD_LEFT; ff < BOARD_RGHT; ff++) {
186 if (flags & F_WHITE_ON_MOVE) {
187 if (!WhitePiece(board[rf][ff])) continue;
189 if (!BlackPiece(board[rf][ff])) continue;
191 m = 0; piece = board[rf][ff];
192 if(PieceToChar(piece) == '~')
193 piece = (ChessSquare) ( DEMOTED piece );
194 if(gameInfo.variant == VariantShogi)
195 piece = (ChessSquare) ( SHOGI piece );
198 /* case EmptySquare: [HGM] this is nonsense, and conflicts with Shogi cases */
200 /* can't happen ([HGM] except for faries...) */
204 if(gameInfo.variant == VariantXiangqi) {
205 /* [HGM] capture and move straight ahead in Xiangqi */
206 if (rf < BOARD_HEIGHT-1 &&
207 !SameColor(board[rf][ff], board[rf + 1][ff]) ) {
208 callback(board, flags, NormalMove,
209 rf, ff, rf + 1, ff, closure);
211 /* and move sideways when across the river */
212 for (s = -1; s <= 1; s += 2) {
213 if (rf >= BOARD_HEIGHT>>1 &&
214 ff + s >= BOARD_LEFT && ff + s < BOARD_RGHT &&
215 !WhitePiece(board[rf][ff+s]) ) {
216 callback(board, flags, NormalMove,
217 rf, ff, rf, ff+s, closure);
222 if (rf < BOARD_HEIGHT-1 && board[rf + 1][ff] == EmptySquare) {
223 callback(board, flags,
224 rf >= BOARD_HEIGHT-1-promoRank ? WhitePromotion : NormalMove,
225 rf, ff, rf + 1, ff, closure);
227 if (rf == 1 && board[2][ff] == EmptySquare &&
228 gameInfo.variant != VariantShatranj && /* [HGM] */
229 gameInfo.variant != VariantCourier && /* [HGM] */
230 board[3][ff] == EmptySquare ) {
231 callback(board, flags, NormalMove,
232 rf, ff, 3, ff, closure);
234 for (s = -1; s <= 1; s += 2) {
235 if (rf < BOARD_HEIGHT-1 && ff + s >= BOARD_LEFT && ff + s < BOARD_RGHT &&
236 ((flags & F_KRIEGSPIEL_CAPTURE) ||
237 BlackPiece(board[rf + 1][ff + s]))) {
238 callback(board, flags,
239 rf >= BOARD_HEIGHT-1-promoRank ? WhitePromotion : NormalMove,
240 rf, ff, rf + 1, ff + s, closure);
242 if (rf == BOARD_HEIGHT-4) {
243 if (ff + s >= BOARD_LEFT && ff + s < BOARD_RGHT &&
244 (epfile == ff + s || epfile == EP_UNKNOWN) &&
245 board[BOARD_HEIGHT-4][ff + s] == BlackPawn &&
246 board[BOARD_HEIGHT-3][ff + s] == EmptySquare) {
247 callback(board, flags, WhiteCapturesEnPassant,
248 rf, ff, 5, ff + s, closure);
255 if(gameInfo.variant == VariantXiangqi) {
256 /* [HGM] capture straight ahead in Xiangqi */
257 if (rf > 0 && !SameColor(board[rf][ff], board[rf - 1][ff]) ) {
258 callback(board, flags, NormalMove,
259 rf, ff, rf - 1, ff, closure);
261 /* and move sideways when across the river */
262 for (s = -1; s <= 1; s += 2) {
263 if (rf < BOARD_HEIGHT>>1 &&
264 ff + s >= BOARD_LEFT && ff + s < BOARD_RGHT &&
265 !BlackPiece(board[rf][ff+s]) ) {
266 callback(board, flags, NormalMove,
267 rf, ff, rf, ff+s, closure);
272 if (rf > 0 && board[rf - 1][ff] == EmptySquare) {
273 callback(board, flags,
274 rf <= promoRank ? BlackPromotion : NormalMove,
275 rf, ff, rf - 1, ff, closure);
277 if (rf == BOARD_HEIGHT-2 && board[BOARD_HEIGHT-3][ff] == EmptySquare &&
278 gameInfo.variant != VariantShatranj && /* [HGM] */
279 gameInfo.variant != VariantCourier && /* [HGM] */
280 board[BOARD_HEIGHT-4][ff] == EmptySquare) {
281 callback(board, flags, NormalMove,
282 rf, ff, BOARD_HEIGHT-4, ff, closure);
284 for (s = -1; s <= 1; s += 2) {
285 if (rf > 0 && ff + s >= BOARD_LEFT && ff + s < BOARD_RGHT &&
286 ((flags & F_KRIEGSPIEL_CAPTURE) ||
287 WhitePiece(board[rf - 1][ff + s]))) {
288 callback(board, flags,
289 rf <= promoRank ? BlackPromotion : NormalMove,
290 rf, ff, rf - 1, ff + s, closure);
293 if (ff + s >= BOARD_LEFT && ff + s < BOARD_RGHT &&
294 (epfile == ff + s || epfile == EP_UNKNOWN) &&
295 board[3][ff + s] == WhitePawn &&
296 board[2][ff + s] == EmptySquare) {
297 callback(board, flags, BlackCapturesEnPassant,
298 rf, ff, 2, ff + s, closure);
309 for (i = -1; i <= 1; i += 2)
310 for (j = -1; j <= 1; j += 2)
311 for (s = 1; s <= 2; s++) {
314 if (!(rt < 0 || rt >= BOARD_HEIGHT || ft < BOARD_LEFT || ft >= BOARD_RGHT)
315 && ( gameInfo.variant != VariantXiangqi || board[rf+i*(s-1)][ff+j*(2-s)] == EmptySquare)
316 && !SameColor(board[rf][ff], board[rt][ft]))
317 callback(board, flags, NormalMove,
318 rf, ff, rt, ft, closure);
322 case SHOGI WhiteKnight:
323 for (s = -1; s <= 1; s += 2) {
324 if (rf < BOARD_HEIGHT-2 && ff + s >= BOARD_LEFT && ff + s < BOARD_RGHT &&
325 !SameColor(board[rf][ff], board[rf + 2][ff + s])) {
326 callback(board, flags, NormalMove,
327 rf, ff, rf + 2, ff + s, closure);
332 case SHOGI BlackKnight:
333 for (s = -1; s <= 1; s += 2) {
334 if (rf > 1 && ff + s >= BOARD_LEFT && ff + s < BOARD_RGHT &&
335 !SameColor(board[rf][ff], board[rf - 2][ff + s])) {
336 callback(board, flags, NormalMove,
337 rf, ff, rf - 2, ff + s, closure);
344 for (d = 0; d <= 1; d++)
345 for (s = -1; s <= 1; s += 2) {
348 rt = rf + (i * s) * d;
349 ft = ff + (i * s) * (1 - d);
350 if (rt < 0 || rt >= BOARD_HEIGHT || ft < BOARD_LEFT || ft >= BOARD_RGHT) break;
351 if (m == 0 && board[rt][ft] == EmptySquare)
352 callback(board, flags, NormalMove,
353 rf, ff, rt, ft, closure);
354 if (m == 1 && board[rt][ft] != EmptySquare &&
355 !SameColor(board[rf][ff], board[rt][ft]) )
356 callback(board, flags, NormalMove,
357 rf, ff, rt, ft, closure);
358 if (board[rt][ft] != EmptySquare && m++) break;
363 /* Gold General (and all its promoted versions) . First do the */
364 /* diagonal forward steps, then proceed as normal Wazir */
365 case SHOGI WhiteWazir:
366 case SHOGI (PROMOTED WhitePawn):
367 case SHOGI (PROMOTED WhiteKnight):
368 case SHOGI (PROMOTED WhiteQueen):
369 case SHOGI (PROMOTED WhiteFerz):
370 for (s = -1; s <= 1; s += 2) {
371 if (rf < BOARD_HEIGHT-1 && ff + s >= BOARD_LEFT && ff + s < BOARD_RGHT &&
372 !SameColor(board[rf][ff], board[rf + 1][ff + s])) {
373 callback(board, flags, NormalMove,
374 rf, ff, rf + 1, ff + s, closure);
379 case SHOGI BlackWazir:
380 case SHOGI (PROMOTED BlackPawn):
381 case SHOGI (PROMOTED BlackKnight):
382 case SHOGI (PROMOTED BlackQueen):
383 case SHOGI (PROMOTED BlackFerz):
384 for (s = -1; s <= 1; s += 2) {
385 if (rf > 0 && ff + s >= BOARD_LEFT && ff + s < BOARD_RGHT &&
386 !SameColor(board[rf][ff], board[rf - 1][ff + s])) {
387 callback(board, flags, NormalMove,
388 rf, ff, rf - 1, ff + s, closure);
395 for (d = 0; d <= 1; d++)
396 for (s = -1; s <= 1; s += 2) {
398 ft = ff + s * (1 - d);
399 if (!(rt < 0 || rt >= BOARD_HEIGHT || ft < BOARD_LEFT || ft >= BOARD_RGHT)
400 && !SameColor(board[rf][ff], board[rt][ft]) &&
401 (gameInfo.variant != VariantXiangqi || InPalace(rt, ft) ) )
402 callback(board, flags, NormalMove,
403 rf, ff, rt, ft, closure);
409 /* [HGM] support Shatranj pieces */
410 for (rs = -1; rs <= 1; rs += 2)
411 for (fs = -1; fs <= 1; fs += 2) {
414 if (!(rt < 0 || rt >= BOARD_HEIGHT || ft < BOARD_LEFT || ft >= BOARD_RGHT)
415 && ( gameInfo.variant != VariantXiangqi ||
416 board[rf+rs][ff+fs] == EmptySquare && (2*rf < BOARD_HEIGHT) == (2*rt < BOARD_HEIGHT) )
418 && !SameColor(board[rf][ff], board[rt][ft]))
419 callback(board, flags, NormalMove,
420 rf, ff, rt, ft, closure);
421 if(gameInfo.variant != VariantFairy && gameInfo.variant != VariantGreat) continue;
422 rt = rf + rs; // in unknown variant we assume Modern Elephant, which can also do one step
424 if (!(rt < 0 || rt >= BOARD_HEIGHT || ft < BOARD_LEFT || ft >= BOARD_RGHT)
425 && !SameColor(board[rf][ff], board[rt][ft]))
426 callback(board, flags, NormalMove,
427 rf, ff, rt, ft, closure);
431 /* Shogi Dragon Horse has to continue with Wazir after Bishop */
432 case SHOGI WhiteCardinal:
433 case SHOGI BlackCardinal:
436 /* Capablanca Archbishop continues as Knight */
441 /* Shogi Bishops are ordinary Bishops */
442 case SHOGI WhiteBishop:
443 case SHOGI BlackBishop:
446 for (rs = -1; rs <= 1; rs += 2)
447 for (fs = -1; fs <= 1; fs += 2)
451 if (rt < 0 || rt >= BOARD_HEIGHT || ft < BOARD_LEFT || ft >= BOARD_RGHT) break;
452 if (SameColor(board[rf][ff], board[rt][ft])) break;
453 callback(board, flags, NormalMove,
454 rf, ff, rt, ft, closure);
455 if (board[rt][ft] != EmptySquare) break;
457 if(m==1) goto mounted;
458 if(m==2) goto finishGold;
459 /* Bishop falls through */
462 /* Shogi Lance is unlike anything, and asymmetric at that */
463 case SHOGI WhiteQueen:
467 if (rt >= BOARD_HEIGHT) break;
468 if (SameColor(board[rf][ff], board[rt][ft])) break;
469 callback(board, flags, NormalMove,
470 rf, ff, rt, ft, closure);
471 if (board[rt][ft] != EmptySquare) break;
475 case SHOGI BlackQueen:
480 if (SameColor(board[rf][ff], board[rt][ft])) break;
481 callback(board, flags, NormalMove,
482 rf, ff, rt, ft, closure);
483 if (board[rt][ft] != EmptySquare) break;
487 /* Make Dragon-King Dababba & Rook-like outside Shogi, for better disambiguation in variant Fairy */
490 for (d = 0; d <= 1; d++) // Dababba moves that Rook cannot do
491 for (s = -2; s <= 2; s += 4) {
493 ft = ff + s * (1 - d);
494 if (rt < 0 || rt >= BOARD_HEIGHT || ft < BOARD_LEFT || ft >= BOARD_RGHT || board[rf+rt>>1][ff+ft>>1] == EmptySquare) continue;
495 if (SameColor(board[rf][ff], board[rt][ft])) continue;
496 callback(board, flags, NormalMove, rf, ff, rt, ft, closure);
500 /* Shogi Dragon King has to continue as Ferz after Rook moves */
501 case SHOGI WhiteDragon:
502 case SHOGI BlackDragon:
505 /* Capablanca Chancellor sets flag to continue as Knight */
510 /* Shogi Rooks are ordinary Rooks */
511 case SHOGI WhiteRook:
512 case SHOGI BlackRook:
516 for (d = 0; d <= 1; d++)
517 for (s = -1; s <= 1; s += 2)
519 rt = rf + (i * s) * d;
520 ft = ff + (i * s) * (1 - d);
521 if (rt < 0 || rt >= BOARD_HEIGHT || ft < BOARD_LEFT || ft >= BOARD_RGHT) break;
522 if (SameColor(board[rf][ff], board[rt][ft])) break;
523 callback(board, flags, NormalMove,
524 rf, ff, rt, ft, closure);
525 if (board[rt][ft] != EmptySquare) break;
527 if(m==1) goto mounted;
528 if(m==2) goto finishSilver;
533 for (rs = -1; rs <= 1; rs++)
534 for (fs = -1; fs <= 1; fs++) {
535 if (rs == 0 && fs == 0) continue;
539 if (rt < 0 || rt >= BOARD_HEIGHT || ft < BOARD_LEFT || ft >= BOARD_RGHT) break;
540 if (SameColor(board[rf][ff], board[rt][ft])) break;
541 callback(board, flags, NormalMove,
542 rf, ff, rt, ft, closure);
543 if (board[rt][ft] != EmptySquare) break;
548 /* Shogi Pawn and Silver General: first the Pawn move, */
549 /* then the General continues like a Ferz */
551 if(gameInfo.variant != VariantMakruk) goto commoner;
552 case SHOGI WhitePawn:
553 case SHOGI WhiteFerz:
554 if (rf < BOARD_HEIGHT-1 &&
555 !SameColor(board[rf][ff], board[rf + 1][ff]) )
556 callback(board, flags, NormalMove,
557 rf, ff, rf + 1, ff, closure);
558 if(piece != SHOGI WhitePawn) goto finishSilver;
562 if(gameInfo.variant != VariantMakruk) goto commoner;
563 case SHOGI BlackPawn:
564 case SHOGI BlackFerz:
566 !SameColor(board[rf][ff], board[rf - 1][ff]) )
567 callback(board, flags, NormalMove,
568 rf, ff, rf - 1, ff, closure);
569 if(piece == SHOGI BlackPawn) break;
574 /* [HGM] support Shatranj pieces */
575 for (rs = -1; rs <= 1; rs += 2)
576 for (fs = -1; fs <= 1; fs += 2) {
579 if (rt < 0 || rt >= BOARD_HEIGHT || ft < BOARD_LEFT || ft >= BOARD_RGHT) continue;
580 if (!SameColor(board[rf][ff], board[rt][ft]) &&
581 (gameInfo.variant != VariantXiangqi || InPalace(rt, ft) ) )
582 callback(board, flags, NormalMove,
583 rf, ff, rt, ft, closure);
589 m++; // [HGM] superchess: use for Centaur
591 case SHOGI WhiteKing:
592 case SHOGI BlackKing:
596 for (i = -1; i <= 1; i++)
597 for (j = -1; j <= 1; j++) {
598 if (i == 0 && j == 0) continue;
601 if (rt < 0 || rt >= BOARD_HEIGHT || ft < BOARD_LEFT || ft >= BOARD_RGHT) continue;
602 if (SameColor(board[rf][ff], board[rt][ft])) continue;
603 callback(board, flags, NormalMove,
604 rf, ff, rt, ft, closure);
606 if(m==1) goto mounted;
609 case WhiteNightrider:
610 case BlackNightrider:
611 for (i = -1; i <= 1; i += 2)
612 for (j = -1; j <= 1; j += 2)
613 for (s = 1; s <= 2; s++) { int k;
617 if (rt < 0 || rt >= BOARD_HEIGHT || ft < BOARD_LEFT || ft >= BOARD_RGHT) break;
618 if (SameColor(board[rf][ff], board[rt][ft])) break;
619 callback(board, flags, NormalMove,
620 rf, ff, rt, ft, closure);
621 if (board[rt][ft] != EmptySquare) break;
625 case WhiteFalcon: // [HGM] wild: for wildcards, self-capture symbolizes move to anywhere
631 callback(board, flags, NormalMove, rf, ff, rf, ff, closure);
644 extern void GenLegalCallback P((Board board, int flags, ChessMove kind,
645 int rf, int ff, int rt, int ft,
648 void GenLegalCallback(board, flags, kind, rf, ff, rt, ft, closure)
655 register GenLegalClosure *cl = (GenLegalClosure *) closure;
657 if (!(flags & F_IGNORE_CHECK) &&
658 CheckTest(board, flags, rf, ff, rt, ft,
659 kind == WhiteCapturesEnPassant ||
660 kind == BlackCapturesEnPassant)) return;
661 if (flags & F_ATOMIC_CAPTURE) {
662 if (board[rt][ft] != EmptySquare ||
663 kind == WhiteCapturesEnPassant || kind == BlackCapturesEnPassant) {
665 ChessSquare king = (flags & F_WHITE_ON_MOVE) ? WhiteKing : BlackKing;
666 if (board[rf][ff] == king) return;
667 for (r = rt-1; r <= rt+1; r++) {
668 for (f = ft-1; f <= ft+1; f++) {
669 if (r >= 0 && r < BOARD_HEIGHT && f >= BOARD_LEFT && f < BOARD_RGHT &&
670 board[r][f] == king) return;
675 cl->cb(board, flags, kind, rf, ff, rt, ft, cl->cl);
682 int captures; // [HGM] losers
683 } LegalityTestClosure;
686 /* Like GenPseudoLegal, but (1) include castling moves, (2) unless
687 F_IGNORE_CHECK is set in the flags, omit moves that would leave the
688 king in check, and (3) if F_ATOMIC_CAPTURE is set in the flags, omit
689 moves that would destroy your own king. The CASTLE_OK flags are
690 true if castling is not yet ruled out by a move of the king or
691 rook. Return TRUE if the player on move is currently in check and
692 F_IGNORE_CHECK is not set. [HGM] add castlingRights parameter */
693 int GenLegal(board, flags, callback, closure)
696 MoveCallback callback;
700 int ff, ft, k, left, right;
701 int ignoreCheck = (flags & F_IGNORE_CHECK) != 0;
702 ChessSquare wKing = WhiteKing, bKing = BlackKing, *castlingRights = board[CASTLING];
706 GenPseudoLegal(board, flags, GenLegalCallback, (VOIDSTAR) &cl);
709 CheckTest(board, flags, -1, -1, -1, -1, FALSE)) return TRUE;
711 /* Generate castling moves */
712 if(gameInfo.variant == VariantKnightmate) { /* [HGM] Knightmate */
713 wKing = WhiteUnicorn; bKing = BlackUnicorn;
716 for (ff = BOARD_WIDTH>>1; ff >= (BOARD_WIDTH-1)>>1; ff-- /*ics wild 1*/) {
717 if ((flags & F_WHITE_ON_MOVE) &&
718 (flags & F_WHITE_KCASTLE_OK) &&
719 board[0][ff] == wKing &&
720 board[0][ff + 1] == EmptySquare &&
721 board[0][ff + 2] == EmptySquare &&
722 board[0][BOARD_RGHT-3] == EmptySquare &&
723 board[0][BOARD_RGHT-2] == EmptySquare &&
724 board[0][BOARD_RGHT-1] == WhiteRook &&
725 castlingRights[0] != NoRights && /* [HGM] check rights */
726 ( castlingRights[2] == ff || castlingRights[6] == ff ) &&
728 (!CheckTest(board, flags, 0, ff, 0, ff + 1, FALSE) &&
729 !CheckTest(board, flags, 0, ff, 0, BOARD_RGHT-3, FALSE) &&
730 (gameInfo.variant != VariantJanus || !CheckTest(board, flags, 0, ff, 0, BOARD_RGHT-2, FALSE)) &&
731 !CheckTest(board, flags, 0, ff, 0, ff + 2, FALSE)))) {
733 callback(board, flags,
734 ff==BOARD_WIDTH>>1 ? WhiteKingSideCastle : WhiteKingSideCastleWild,
735 0, ff, 0, ff + ((gameInfo.boardWidth+2)>>2) + (gameInfo.variant == VariantJanus), closure);
737 if ((flags & F_WHITE_ON_MOVE) &&
738 (flags & F_WHITE_QCASTLE_OK) &&
739 board[0][ff] == wKing &&
740 board[0][ff - 1] == EmptySquare &&
741 board[0][ff - 2] == EmptySquare &&
742 board[0][BOARD_LEFT+2] == EmptySquare &&
743 board[0][BOARD_LEFT+1] == EmptySquare &&
744 board[0][BOARD_LEFT+0] == WhiteRook &&
745 castlingRights[1] != NoRights && /* [HGM] check rights */
746 ( castlingRights[2] == ff || castlingRights[6] == ff ) &&
748 (!CheckTest(board, flags, 0, ff, 0, ff - 1, FALSE) &&
749 !CheckTest(board, flags, 0, ff, 0, BOARD_LEFT+3, FALSE) &&
750 !CheckTest(board, flags, 0, ff, 0, ff - 2, FALSE)))) {
752 callback(board, flags,
753 ff==BOARD_WIDTH>>1 ? WhiteQueenSideCastle : WhiteQueenSideCastleWild,
754 0, ff, 0, ff - ((gameInfo.boardWidth+2)>>2), closure);
756 if (!(flags & F_WHITE_ON_MOVE) &&
757 (flags & F_BLACK_KCASTLE_OK) &&
758 board[BOARD_HEIGHT-1][ff] == bKing &&
759 board[BOARD_HEIGHT-1][ff + 1] == EmptySquare &&
760 board[BOARD_HEIGHT-1][ff + 2] == EmptySquare &&
761 board[BOARD_HEIGHT-1][BOARD_RGHT-3] == EmptySquare &&
762 board[BOARD_HEIGHT-1][BOARD_RGHT-2] == EmptySquare &&
763 board[BOARD_HEIGHT-1][BOARD_RGHT-1] == BlackRook &&
764 castlingRights[3] != NoRights && /* [HGM] check rights */
765 ( castlingRights[5] == ff || castlingRights[7] == ff ) &&
767 (!CheckTest(board, flags, BOARD_HEIGHT-1, ff, BOARD_HEIGHT-1, ff + 1, FALSE) &&
768 !CheckTest(board, flags, BOARD_HEIGHT-1, ff, BOARD_HEIGHT-1, BOARD_RGHT-3, FALSE) &&
769 (gameInfo.variant != VariantJanus || !CheckTest(board, flags, BOARD_HEIGHT-1, ff, BOARD_HEIGHT-1, BOARD_RGHT-2, FALSE)) &&
770 !CheckTest(board, flags, BOARD_HEIGHT-1, ff, BOARD_HEIGHT-1, ff + 2, FALSE)))) {
772 callback(board, flags,
773 ff==BOARD_WIDTH>>1 ? BlackKingSideCastle : BlackKingSideCastleWild,
774 BOARD_HEIGHT-1, ff, BOARD_HEIGHT-1, ff + ((gameInfo.boardWidth+2)>>2) + (gameInfo.variant == VariantJanus), closure);
776 if (!(flags & F_WHITE_ON_MOVE) &&
777 (flags & F_BLACK_QCASTLE_OK) &&
778 board[BOARD_HEIGHT-1][ff] == bKing &&
779 board[BOARD_HEIGHT-1][ff - 1] == EmptySquare &&
780 board[BOARD_HEIGHT-1][ff - 2] == EmptySquare &&
781 board[BOARD_HEIGHT-1][BOARD_LEFT+2] == EmptySquare &&
782 board[BOARD_HEIGHT-1][BOARD_LEFT+1] == EmptySquare &&
783 board[BOARD_HEIGHT-1][BOARD_LEFT+0] == BlackRook &&
784 castlingRights[4] != NoRights && /* [HGM] check rights */
785 ( castlingRights[5] == ff || castlingRights[7] == ff ) &&
787 (!CheckTest(board, flags, BOARD_HEIGHT-1, ff, BOARD_HEIGHT-1, ff - 1, FALSE) &&
788 !CheckTest(board, flags, BOARD_HEIGHT-1, ff, BOARD_HEIGHT-1, BOARD_LEFT+3, FALSE) &&
789 !CheckTest(board, flags, BOARD_HEIGHT-1, ff, BOARD_HEIGHT-1, ff - 2, FALSE)))) {
791 callback(board, flags,
792 ff==BOARD_WIDTH>>1 ? BlackQueenSideCastle : BlackQueenSideCastleWild,
793 BOARD_HEIGHT-1, ff, BOARD_HEIGHT-1, ff - ((gameInfo.boardWidth+2)>>2), closure);
797 if(flags & F_FRC_TYPE_CASTLING) {
799 /* generate all potential FRC castling moves (KxR), ignoring flags */
800 /* [HGM] test if the Rooks we find have castling rights */
803 if ((flags & F_WHITE_ON_MOVE) != 0) {
804 ff = castlingRights[2]; /* King file if we have any rights */
805 if(ff != NoRights && board[0][ff] == WhiteKing) {
806 if (appData.debugMode) {
807 fprintf(debugFP, "FRC castling, %d %d %d %d %d %d\n",
808 castlingRights[0],castlingRights[1],ff,castlingRights[3],castlingRights[4],castlingRights[5]);
810 ft = castlingRights[0]; /* Rook file if we have H-side rights */
812 right = BOARD_RGHT-2;
813 if(ff == BOARD_RGHT-2) left = right = ff-1; /* special case */
814 for(k=left; k<=right && ft != NoRights; k++) /* first test if blocked */
815 if(k != ft && board[0][k] != EmptySquare) ft = NoRights;
816 for(k=left; k<right && ft != NoRights; k++) /* then if not checked */
817 if(!ignoreCheck && CheckTest(board, flags, 0, ff, 0, k, FALSE)) ft = NoRights;
818 if(ft != NoRights && board[0][ft] == WhiteRook)
819 callback(board, flags, WhiteHSideCastleFR, 0, ff, 0, ft, closure);
821 ft = castlingRights[1]; /* Rook file if we have A-side rights */
824 if(ff <= BOARD_LEFT+2) { left = ff+1; right = BOARD_LEFT+3; }
825 for(k=left; k<=right && ft != NoRights; k++) /* first test if blocked */
826 if(k != ft && board[0][k] != EmptySquare) ft = NoRights;
827 if(ff > BOARD_LEFT+2)
828 for(k=left+1; k<=right && ft != NoRights; k++) /* then if not checked */
829 if(!ignoreCheck && CheckTest(board, flags, 0, ff, 0, k, FALSE)) ft = NoRights;
830 if(ft != NoRights && board[0][ft] == WhiteRook)
831 callback(board, flags, WhiteASideCastleFR, 0, ff, 0, ft, closure);
834 ff = castlingRights[5]; /* King file if we have any rights */
835 if(ff != NoRights && board[BOARD_HEIGHT-1][ff] == BlackKing) {
836 ft = castlingRights[3]; /* Rook file if we have H-side rights */
838 right = BOARD_RGHT-2;
839 if(ff == BOARD_RGHT-2) left = right = ff-1; /* special case */
840 for(k=left; k<=right && ft != NoRights; k++) /* first test if blocked */
841 if(k != ft && board[BOARD_HEIGHT-1][k] != EmptySquare) ft = NoRights;
842 for(k=left; k<right && ft != NoRights; k++) /* then if not checked */
843 if(!ignoreCheck && CheckTest(board, flags, BOARD_HEIGHT-1, ff, BOARD_HEIGHT-1, k, FALSE)) ft = NoRights;
844 if(ft != NoRights && board[BOARD_HEIGHT-1][ft] == BlackRook)
845 callback(board, flags, BlackHSideCastleFR, BOARD_HEIGHT-1, ff, BOARD_HEIGHT-1, ft, closure);
847 ft = castlingRights[4]; /* Rook file if we have A-side rights */
850 if(ff <= BOARD_LEFT+2) { left = ff+1; right = BOARD_LEFT+3; }
851 for(k=left; k<=right && ft != NoRights; k++) /* first test if blocked */
852 if(k != ft && board[BOARD_HEIGHT-1][k] != EmptySquare) ft = NoRights;
853 if(ff > BOARD_LEFT+2)
854 for(k=left+1; k<=right && ft != NoRights; k++) /* then if not checked */
855 if(!ignoreCheck && CheckTest(board, flags, BOARD_HEIGHT-1, ff, BOARD_HEIGHT-1, k, FALSE)) ft = NoRights;
856 if(ft != NoRights && board[BOARD_HEIGHT-1][ft] == BlackRook)
857 callback(board, flags, BlackASideCastleFR, BOARD_HEIGHT-1, ff, BOARD_HEIGHT-1, ft, closure);
873 extern void CheckTestCallback P((Board board, int flags, ChessMove kind,
874 int rf, int ff, int rt, int ft,
878 void CheckTestCallback(board, flags, kind, rf, ff, rt, ft, closure)
885 register CheckTestClosure *cl = (CheckTestClosure *) closure;
887 if (rt == cl->rking && ft == cl->fking) cl->check++;
891 /* If the player on move were to move from (rf, ff) to (rt, ft), would
892 he leave himself in check? Or if rf == -1, is the player on move
893 in check now? enPassant must be TRUE if the indicated move is an
894 e.p. capture. The possibility of castling out of a check along the
895 back rank is not accounted for (i.e., we still return nonzero), as
896 this is illegal anyway. Return value is the number of times the
898 int CheckTest(board, flags, rf, ff, rt, ft, enPassant)
901 int rf, ff, rt, ft, enPassant;
904 ChessSquare king = flags & F_WHITE_ON_MOVE ? WhiteKing : BlackKing;
905 ChessSquare captured = EmptySquare;
906 /* Suppress warnings on uninitialized variables */
908 if(gameInfo.variant == VariantXiangqi)
909 king = flags & F_WHITE_ON_MOVE ? WhiteWazir : BlackWazir;
910 if(gameInfo.variant == VariantKnightmate)
911 king = flags & F_WHITE_ON_MOVE ? WhiteUnicorn : BlackUnicorn;
915 captured = board[rf][ft];
916 board[rf][ft] = EmptySquare;
918 captured = board[rt][ft];
920 board[rt][ft] = board[rf][ff];
921 board[rf][ff] = EmptySquare;
922 } else board[rt][ft] = ff; // [HGM] drop
924 /* For compatibility with ICS wild 9, we scan the board in the
925 order a1, a2, a3, ... b1, b2, ..., h8 to find the first king,
926 and we test only whether that one is in check. */
928 for (cl.fking = BOARD_LEFT+0; cl.fking < BOARD_RGHT; cl.fking++)
929 for (cl.rking = 0; cl.rking < BOARD_HEIGHT; cl.rking++) {
930 if (board[cl.rking][cl.fking] == king) {
931 if(gameInfo.variant == VariantXiangqi) {
932 /* [HGM] In Xiangqi opposing Kings means check as well */
934 dir = (king >= BlackPawn) ? -1 : 1;
935 for( i=cl.rking+dir; i>=0 && i<BOARD_HEIGHT &&
936 board[i][cl.fking] == EmptySquare; i+=dir );
937 if(i>=0 && i<BOARD_HEIGHT &&
938 board[i][cl.fking] == (dir>0 ? BlackWazir : WhiteWazir) )
942 GenPseudoLegal(board, flags ^ F_WHITE_ON_MOVE, CheckTestCallback, (VOIDSTAR) &cl);
943 goto undo_move; /* 2-level break */
950 board[rf][ff] = board[rt][ft];
952 board[rf][ft] = captured;
953 board[rt][ft] = EmptySquare;
955 board[rt][ft] = captured;
957 } else board[rt][ft] = EmptySquare; // [HGM] drop
959 return cl.fking < BOARD_RGHT ? cl.check : 1000; // [HGM] atomic: return 1000 if we have no king
962 ChessMove LegalDrop(board, flags, piece, rt, ft)
967 { // [HGM] put drop legality testing in separate routine for clarity
969 if(appData.debugMode) fprintf(debugFP, "LegalDrop: %d @ %d,%d)\n", piece, ft, rt);
970 if(board[rt][ft] != EmptySquare) return ImpossibleMove; // must drop to empty square
971 n = PieceToNumber(piece);
972 if(gameInfo.holdingsWidth == 0 || (flags & F_WHITE_ON_MOVE ? board[n][BOARD_WIDTH-1] : board[BOARD_HEIGHT-1-n][0]) != piece)
973 return ImpossibleMove; // piece not available
974 if(gameInfo.variant == VariantShogi) { // in Shogi lots of drops are forbidden!
975 if((piece == WhitePawn || piece == WhiteQueen) && rt == BOARD_HEIGHT-1 ||
976 (piece == BlackPawn || piece == BlackQueen) && rt == 0 ||
977 piece == WhiteKnight && rt > BOARD_HEIGHT-3 ||
978 piece == BlackKnight && rt < 2 ) return IllegalMove; // e.g. where dropped piece has no moves
979 if(piece == WhitePawn || piece == BlackPawn) {
981 for(r=1; r<BOARD_HEIGHT-1; r++)
982 if(board[r][ft] == piece) return IllegalMove; // or there already is a Pawn in file
983 // should still test if we mate with this Pawn
986 if( (piece == WhitePawn || piece == BlackPawn) &&
987 (rt == 0 || rt == BOARD_HEIGHT -1 ) )
988 return IllegalMove; /* no pawn drops on 1st/8th */
990 if(appData.debugMode) fprintf(debugFP, "LegalDrop: %d @ %d,%d)\n", piece, ft, rt);
991 if (!(flags & F_IGNORE_CHECK) &&
992 CheckTest(board, flags, DROP_RANK, piece, rt, ft, FALSE) ) return IllegalMove;
993 return flags & F_WHITE_ON_MOVE ? WhiteDrop : BlackDrop;
996 extern void LegalityTestCallback P((Board board, int flags, ChessMove kind,
997 int rf, int ff, int rt, int ft,
1000 void LegalityTestCallback(board, flags, kind, rf, ff, rt, ft, closure)
1007 register LegalityTestClosure *cl = (LegalityTestClosure *) closure;
1009 // if (appData.debugMode) {
1010 // fprintf(debugFP, "Legality test: %c%c%c%c\n", ff+AAA, rf+ONE, ft+AAA, rt+ONE);
1012 if(board[rt][ft] != EmptySquare || kind==WhiteCapturesEnPassant || kind==BlackCapturesEnPassant)
1013 cl->captures++; // [HGM] losers: count legal captures
1014 if (rf == cl->rf && ff == cl->ff && rt == cl->rt && ft == cl->ft)
1018 ChessMove LegalityTest(board, flags, rf, ff, rt, ft, promoChar)
1021 int rf, ff, rt, ft, promoChar;
1023 LegalityTestClosure cl; ChessSquare piece, *castlingRights = board[CASTLING];
1025 if(rf == DROP_RANK) return LegalDrop(board, flags, ff, rt, ft);
1026 piece = board[rf][ff];
1028 if (appData.debugMode) {
1030 for(i=0; i<6; i++) fprintf(debugFP, "%d ", castlingRights[i]);
1031 fprintf(debugFP, "Legality test? %c%c%c%c\n", ff+AAA, rf+ONE, ft+AAA, rt+ONE);
1033 /* [HGM] Lance, Cobra and Falcon are wildcard pieces; consider all their moves legal */
1034 /* (perhaps we should disallow moves that obviously leave us in check?) */
1035 if(piece == WhiteFalcon || piece == BlackFalcon ||
1036 piece == WhiteCobra || piece == BlackCobra ||
1037 piece == WhiteLance || piece == BlackLance)
1038 return CheckTest(board, flags, rf, ff, rt, ft, FALSE) ? IllegalMove : NormalMove;
1044 cl.kind = IllegalMove;
1045 cl.captures = 0; // [HGM] losers: prepare to count legal captures.
1046 GenLegal(board, flags, LegalityTestCallback, (VOIDSTAR) &cl);
1047 if((flags & F_MANDATORY_CAPTURE) && cl.captures && board[rt][ft] == EmptySquare
1048 && cl.kind != WhiteCapturesEnPassant && cl.kind != BlackCapturesEnPassant)
1049 return(IllegalMove); // [HGM] losers: if there are legal captures, non-capts are illegal
1051 if(promoChar == 'x') promoChar = NULLCHAR; // [HGM] is this ever the case?
1052 if(gameInfo.variant == VariantShogi) {
1053 /* [HGM] Shogi promotions. '=' means defer */
1054 if(rf != DROP_RANK && cl.kind == NormalMove) {
1055 ChessSquare piece = board[rf][ff];
1057 if(promoChar == PieceToChar(BlackQueen)) promoChar = NULLCHAR; /* [HGM] Kludge */
1058 if(promoChar == 'd' && (piece == WhiteRook || piece == BlackRook) ||
1059 promoChar == 'h' && (piece == WhiteBishop || piece == BlackBishop) ||
1060 promoChar == 'g' && (piece <= WhiteFerz || piece <= BlackFerz && piece >= BlackPawn) )
1061 promoChar = '+'; // allowed ICS notations
1062 if(appData.debugMode)fprintf(debugFP,"SHOGI promoChar = %c\n", promoChar ? promoChar : '-');
1063 if(promoChar != NULLCHAR && promoChar != '+' && promoChar != '=')
1064 return CharToPiece(promoChar) == EmptySquare ? ImpossibleMove : IllegalMove;
1065 else if(flags & F_WHITE_ON_MOVE) {
1066 if( (int) piece < (int) WhiteWazir &&
1067 (rf >= BOARD_HEIGHT*2/3 || rt >= BOARD_HEIGHT*2/3) ) {
1068 if( (piece == WhitePawn || piece == WhiteQueen) && rt > BOARD_HEIGHT-2 ||
1069 piece == WhiteKnight && rt > BOARD_HEIGHT-3) /* promotion mandatory */
1070 cl.kind = promoChar == '=' ? IllegalMove : WhitePromotion;
1071 else /* promotion optional, default is defer */
1072 cl.kind = promoChar == '+' ? WhitePromotion : WhiteNonPromotion;
1073 } else cl.kind = promoChar == '+' ? IllegalMove : NormalMove;
1075 if( (int) piece < (int) BlackWazir && (rf < BOARD_HEIGHT/3 || rt < BOARD_HEIGHT/3) ) {
1076 if( (piece == BlackPawn || piece == BlackQueen) && rt < 1 ||
1077 piece == BlackKnight && rt < 2 ) /* promotion obligatory */
1078 cl.kind = promoChar == '=' ? IllegalMove : BlackPromotion;
1079 else /* promotion optional, default is defer */
1080 cl.kind = promoChar == '+' ? BlackPromotion : BlackNonPromotion;
1081 } else cl.kind = promoChar == '+' ? IllegalMove : NormalMove;
1085 if (promoChar != NULLCHAR) {
1086 if(promoChar == '=') cl.kind = IllegalMove; else // [HGM] shogi: no deferred promotion outside Shogi
1087 if (cl.kind == WhitePromotion || cl.kind == BlackPromotion) {
1088 if(CharToPiece(flags & F_WHITE_ON_MOVE ? ToUpper(promoChar) : ToLower(promoChar)) == EmptySquare)
1089 cl.kind = ImpossibleMove; // non-existing piece
1091 cl.kind = IllegalMove;
1101 extern void MateTestCallback P((Board board, int flags, ChessMove kind,
1102 int rf, int ff, int rt, int ft,
1105 void MateTestCallback(board, flags, kind, rf, ff, rt, ft, closure)
1112 register MateTestClosure *cl = (MateTestClosure *) closure;
1117 /* Return MT_NONE, MT_CHECK, MT_CHECKMATE, or MT_STALEMATE */
1118 int MateTest(board, flags)
1123 int inCheck, r, f, myPieces=0, hisPieces=0, nrKing=0;
1124 ChessSquare king = flags & F_WHITE_ON_MOVE ? WhiteKing : BlackKing;
1126 for(r=0; r<BOARD_HEIGHT; r++) for(f=BOARD_LEFT; f<BOARD_RGHT; f++) {
1127 // [HGM] losers: Count pieces and kings, to detect other unorthodox winning conditions
1128 nrKing += (board[r][f] == king); // stm has king
1129 if( board[r][f] != EmptySquare ) {
1130 if((int)board[r][f] <= (int)king && (int)board[r][f] >= (int)king - (int)WhiteKing + (int)WhitePawn)
1135 if(appData.debugMode) fprintf(debugFP, "MateTest: K=%d, my=%d, his=%d\n", nrKing, myPieces, hisPieces);
1136 switch(gameInfo.variant) { // [HGM] losers: extinction wins
1137 case VariantShatranj:
1138 if(hisPieces == 1) return myPieces > 1 ? MT_BARE : MT_DRAW;
1142 if(nrKing == 0) return MT_NOKING;
1145 if(myPieces == 1) return MT_BARE;
1148 inCheck = GenLegal(board, flags, MateTestCallback, (VOIDSTAR) &cl);
1149 // [HGM] 3check: yet to do!
1151 return inCheck ? MT_CHECK : MT_NONE;
1153 if(gameInfo.holdingsWidth && gameInfo.variant != VariantSuper || gameInfo.variant != VariantGreat) { // drop game
1154 int r, f, n, holdings = flags & F_WHITE_ON_MOVE ? BOARD_WIDTH-1 : 0;
1155 for(r=0; r<BOARD_HEIGHT; r++) for(f=BOARD_LEFT; f<BOARD_RGHT; f++) if(board[r][f] == EmptySquare) // all empty squares
1156 for(n=0; n<BOARD_HEIGHT; n++) // all pieces in hand
1157 if(board[n][holdings] != EmptySquare) {
1158 int moveType = LegalDrop(board, flags, board[n][holdings], r, f);
1159 if(moveType == WhiteDrop || moveType == BlackDrop) return MT_CHECK; // we can resolve check by legal drop
1162 if(gameInfo.variant == VariantSuicide) // [HGM] losers: always stalemate, since no check, but result varies
1163 return myPieces == hisPieces ? MT_STALEMATE :
1164 myPieces > hisPieces ? MT_STAINMATE : MT_STEALMATE;
1165 else if(gameInfo.variant == VariantLosers) return inCheck ? MT_TRICKMATE : MT_STEALMATE;
1166 else if(gameInfo.variant == VariantGiveaway) return MT_STEALMATE; // no check exists, stalemated = win
1168 return inCheck ? MT_CHECKMATE
1169 : (gameInfo.variant == VariantXiangqi || gameInfo.variant == VariantShatranj) ?
1170 MT_STAINMATE : MT_STALEMATE;
1175 extern void DisambiguateCallback P((Board board, int flags, ChessMove kind,
1176 int rf, int ff, int rt, int ft,
1179 void DisambiguateCallback(board, flags, kind, rf, ff, rt, ft, closure)
1186 register DisambiguateClosure *cl = (DisambiguateClosure *) closure;
1187 int wildCard = FALSE; ChessSquare piece = board[rf][ff];
1189 // [HGM] wild: for wild-card pieces rt and rf are dummies
1190 if(piece == WhiteFalcon || piece == BlackFalcon ||
1191 piece == WhiteCobra || piece == BlackCobra ||
1192 piece == WhiteLance || piece == BlackLance)
1195 if ((cl->pieceIn == EmptySquare || cl->pieceIn == board[rf][ff]
1196 || PieceToChar(board[rf][ff]) == '~'
1197 && cl->pieceIn == (ChessSquare)(DEMOTED board[rf][ff])
1199 (cl->rfIn == -1 || cl->rfIn == rf) &&
1200 (cl->ffIn == -1 || cl->ffIn == ff) &&
1201 (cl->rtIn == -1 || cl->rtIn == rt || wildCard) &&
1202 (cl->ftIn == -1 || cl->ftIn == ft || wildCard)) {
1205 if(cl->count == 1 || board[rt][ft] != EmptySquare) {
1206 // [HGM] oneclick: if multiple moves, be sure we remember capture
1207 cl->piece = board[rf][ff];
1210 cl->rt = wildCard ? cl->rtIn : rt;
1211 cl->ft = wildCard ? cl->ftIn : ft;
1214 cl->captures += (board[cl->rt][cl->ft] != EmptySquare); // [HGM] oneclick: count captures
1218 void Disambiguate(board, flags, closure)
1221 DisambiguateClosure *closure;
1223 int illegal = 0; char c = closure->promoCharIn;
1225 closure->count = closure->captures = 0;
1226 closure->rf = closure->ff = closure->rt = closure->ft = 0;
1227 closure->kind = ImpossibleMove;
1228 if (appData.debugMode) {
1229 fprintf(debugFP, "Disambiguate in: %d(%d,%d)-(%d,%d) = %d (%c)\n",
1230 closure->pieceIn,closure->ffIn,closure->rfIn,closure->ftIn,closure->rtIn,
1231 closure->promoCharIn, closure->promoCharIn >= ' ' ? closure->promoCharIn : '-');
1233 GenLegal(board, flags, DisambiguateCallback, (VOIDSTAR) closure);
1234 if (closure->count == 0) {
1235 /* See if it's an illegal move due to check */
1237 GenLegal(board, flags|F_IGNORE_CHECK, DisambiguateCallback, (VOIDSTAR) closure);
1238 if (closure->count == 0) {
1239 /* No, it's not even that */
1240 if (appData.debugMode) { int i, j;
1241 for(i=BOARD_HEIGHT-1; i>=0; i--) {
1242 for(j=0; j<BOARD_WIDTH; j++)
1243 fprintf(debugFP, "%3d", (int) board[i][j]);
1244 fprintf(debugFP, "\n");
1251 if (c == 'x') c = NULLCHAR; // get rid of any 'x' (which should never happen?)
1252 if(gameInfo.variant == VariantShogi) {
1253 /* [HGM] Shogi promotions. On input, '=' means defer, '+' promote. Afterwards, c is set to '+' for promotions, NULL other */
1254 if(closure->rfIn != DROP_RANK && closure->kind == NormalMove) {
1255 ChessSquare piece = closure->piece;
1256 if (c == 'd' && (piece == WhiteRook || piece == BlackRook) ||
1257 c == 'h' && (piece == WhiteBishop || piece == BlackBishop) ||
1258 c == 'g' && (piece <= WhiteFerz || piece <= BlackFerz && piece >= BlackPawn) )
1259 c = '+'; // allowed ICS notations
1260 if(c != NULLCHAR && c != '+' && c != '=') closure->kind = IllegalMove; // otherwise specifying a piece is illegal
1261 else if(flags & F_WHITE_ON_MOVE) {
1262 if( (int) piece < (int) WhiteWazir &&
1263 (closure->rf >= BOARD_HEIGHT-(BOARD_HEIGHT/3) || closure->rt >= BOARD_HEIGHT-(BOARD_HEIGHT/3)) ) {
1264 if( (piece == WhitePawn || piece == WhiteQueen) && closure->rt > BOARD_HEIGHT-2 ||
1265 piece == WhiteKnight && closure->rt > BOARD_HEIGHT-3) /* promotion mandatory */
1266 closure->kind = c == '=' ? IllegalMove : WhitePromotion;
1267 else /* promotion optional, default is defer */
1268 closure->kind = c == '+' ? WhitePromotion : WhiteNonPromotion;
1269 } else closure->kind = c == '+' ? IllegalMove : NormalMove;
1271 if( (int) piece < (int) BlackWazir && (closure->rf < BOARD_HEIGHT/3 || closure->rt < BOARD_HEIGHT/3) ) {
1272 if( (piece == BlackPawn || piece == BlackQueen) && closure->rt < 1 ||
1273 piece == BlackKnight && closure->rt < 2 ) /* promotion obligatory */
1274 closure->kind = c == '=' ? IllegalMove : BlackPromotion;
1275 else /* promotion optional, default is defer */
1276 closure->kind = c == '+' ? BlackPromotion : BlackNonPromotion;
1277 } else closure->kind = c == '+' ? IllegalMove : NormalMove;
1280 if(closure->kind == WhitePromotion || closure->kind == BlackPromotion) c = '+'; else
1281 if(closure->kind == WhiteNonPromotion || closure->kind == BlackNonPromotion) c = '=';
1283 if (closure->kind == WhitePromotion || closure->kind == BlackPromotion) {
1284 if(c == NULLCHAR) { // missing promoChar on mandatory promotion; use default for variant
1285 if(gameInfo.variant == VariantShatranj || gameInfo.variant == VariantCourier || gameInfo.variant == VariantMakruk)
1286 c = PieceToChar(BlackFerz);
1287 else if(gameInfo.variant == VariantGreat)
1288 c = PieceToChar(BlackMan);
1290 c = PieceToChar(BlackQueen);
1291 } else if(c == '=') closure->kind = IllegalMove; // no deferral outside Shogi
1292 } else if (c != NULLCHAR) closure->kind = IllegalMove;
1294 closure->promoChar = ToLower(c); // this can be NULLCHAR! Note we keep original promoChar even if illegal.
1295 if(c != '+' && c != '=' && c != NULLCHAR && CharToPiece(flags & F_WHITE_ON_MOVE ? ToUpper(c) : ToLower(c)) == EmptySquare)
1296 closure->kind = ImpossibleMove; // but we cannot handle non-existing piece types!
1297 if (closure->count > 1) {
1298 closure->kind = AmbiguousMove;
1301 /* Note: If more than one illegal move matches, but no legal
1302 moves, we return IllegalMove, not AmbiguousMove. Caller
1303 can look at closure->count to detect this.
1305 closure->kind = IllegalMove;
1307 if (appData.debugMode) {
1308 fprintf(debugFP, "Disambiguate out: %d(%d,%d)-(%d,%d) = %d (%c)\n",
1309 closure->piece,closure->ff,closure->rf,closure->ft,closure->rt,closure->promoChar,
1310 closure->promoChar >= ' ' ? closure->promoChar:'-');
1324 } CoordsToAlgebraicClosure;
1326 extern void CoordsToAlgebraicCallback P((Board board, int flags,
1327 ChessMove kind, int rf, int ff,
1328 int rt, int ft, VOIDSTAR closure));
1330 void CoordsToAlgebraicCallback(board, flags, kind, rf, ff, rt, ft, closure)
1337 register CoordsToAlgebraicClosure *cl =
1338 (CoordsToAlgebraicClosure *) closure;
1340 if (rt == cl->rt && ft == cl->ft &&
1341 (board[rf][ff] == cl->piece
1342 || PieceToChar(board[rf][ff]) == '~' &&
1343 (ChessSquare) (DEMOTED board[rf][ff]) == cl->piece)
1347 cl->kind = kind; /* this is the move we want */
1349 cl->file++; /* need file to rule out this move */
1353 cl->rank++; /* need rank to rule out this move */
1355 cl->either++; /* rank or file will rule out this move */
1361 /* Convert coordinates to normal algebraic notation.
1362 promoChar must be NULLCHAR or 'x' if not a promotion.
1364 ChessMove CoordsToAlgebraic(board, flags, rf, ff, rt, ft, promoChar, out)
1373 char *outp = out, c;
1374 CoordsToAlgebraicClosure cl;
1376 if (rf == DROP_RANK) {
1377 /* Bughouse piece drop */
1378 *outp++ = ToUpper(PieceToChar((ChessSquare) ff));
1383 else { *outp++ = (rt+ONE-'0')/10 + '0';*outp++ = (rt+ONE-'0')%10 + '0'; }
1385 return (flags & F_WHITE_ON_MOVE) ? WhiteDrop : BlackDrop;
1388 if (promoChar == 'x') promoChar = NULLCHAR;
1389 piece = board[rf][ff];
1390 if(PieceToChar(piece)=='~') piece = (ChessSquare)(DEMOTED piece);
1392 if (appData.debugMode)
1393 fprintf(debugFP, "CoordsToAlgebraic, piece=%d (%d,%d)-(%d,%d) %c\n", (int)piece,ff,rf,ft,rt,promoChar >= ' ' ? promoChar : '-');
1397 kind = LegalityTest(board, flags, rf, ff, rt, ft, promoChar);
1398 if (kind == IllegalMove && !(flags&F_IGNORE_CHECK)) {
1399 /* Keep short notation if move is illegal only because it
1400 leaves the player in check, but still return IllegalMove */
1401 kind = LegalityTest(board, flags|F_IGNORE_CHECK, rf, ff, rt, ft, promoChar);
1402 if (kind == IllegalMove) break;
1407 if (ff == ft && board[rt][ft] == EmptySquare) { /* [HGM] Xiangqi has straight noncapts! */
1408 /* Non-capture; use style "e5" */
1411 else { *outp++ = (rt+ONE-'0')/10 + '0';*outp++ = (rt+ONE-'0')%10 + '0'; }
1413 /* Capture; use style "exd5" */
1414 if(gameInfo.variant != VariantXiangqi || board[rt][ft] != EmptySquare )
1415 *outp++ = 'x'; /* [HGM] Xiangqi has sideway noncaptures across river! */
1419 else { *outp++ = (rt+ONE-'0')/10 + '0';*outp++ = (rt+ONE-'0')%10 + '0'; }
1421 /* Use promotion suffix style "=Q" */
1423 if (appData.debugMode)
1424 fprintf(debugFP, "movetype=%d, promochar=%d=%c\n", (int)kind, promoChar, promoChar >= ' ' ? promoChar : '-');
1425 if (promoChar != NULLCHAR) {
1426 if(gameInfo.variant == VariantShogi) {
1427 /* [HGM] ... but not in Shogi! */
1428 *outp++ = promoChar == '=' ? '=' : '+';
1431 *outp++ = ToUpper(promoChar);
1440 /* Fabien moved code: FRC castling first (if KxR), wild castling second */
1441 /* Code added by Tord: FRC castling. */
1442 if((piece == WhiteKing && board[rt][ft] == WhiteRook) ||
1443 (piece == BlackKing && board[rt][ft] == BlackRook)) {
1445 safeStrCpy(out, "O-O", MOVE_LEN);
1447 safeStrCpy(out, "O-O-O", MOVE_LEN);
1448 return LegalityTest(board, flags, rf, ff, rt, ft, promoChar);
1450 /* End of code added by Tord */
1451 /* Test for castling or ICS wild castling */
1452 /* Use style "O-O" (oh-oh) for PGN compatibility */
1453 else if (rf == rt &&
1454 rf == ((piece == WhiteKing) ? 0 : BOARD_HEIGHT-1) &&
1455 (ft - ff > 1 || ff - ft > 1) && // No castling if legal King move (on narrow boards!)
1456 ((ff == BOARD_WIDTH>>1 && (ft == BOARD_LEFT+2 || ft == BOARD_RGHT-2)) ||
1457 (ff == (BOARD_WIDTH-1)>>1 && (ft == BOARD_LEFT+1 || ft == BOARD_RGHT-3)))) {
1458 if(ft==BOARD_LEFT+1 || ft==BOARD_RGHT-2)
1459 safeStrCpy(out, "O-O", MOVE_LEN);
1461 safeStrCpy(out, "O-O-O", MOVE_LEN);
1463 /* This notation is always unambiguous, unless there are
1464 kings on both the d and e files, with "wild castling"
1465 possible for the king on the d file and normal castling
1466 possible for the other. ICS rules for wild 9
1467 effectively make castling illegal for either king in
1468 this situation. So I am not going to worry about it;
1469 I'll just generate an ambiguous O-O in this case.
1471 return LegalityTest(board, flags, rf, ff, rt, ft, promoChar);
1474 /* else fall through */
1482 cl.kind = IllegalMove;
1483 cl.rank = cl.file = cl.either = 0;
1484 GenLegal(board, flags, CoordsToAlgebraicCallback, (VOIDSTAR) &cl);
1486 if (cl.kind == IllegalMove && !(flags&F_IGNORE_CHECK)) {
1487 /* Generate pretty moves for moving into check, but
1488 still return IllegalMove.
1490 GenLegal(board, flags|F_IGNORE_CHECK, CoordsToAlgebraicCallback, (VOIDSTAR) &cl);
1491 if (cl.kind == IllegalMove) break;
1492 cl.kind = IllegalMove;
1495 /* Style is "Nf3" or "Nxf7" if this is unambiguous,
1496 else "Ngf3" or "Ngxf7",
1497 else "N1f3" or "N5xf7",
1498 else "Ng1f3" or "Ng5xf7".
1500 c = PieceToChar(piece) ;
1501 if( c == '~' || c == '+') {
1502 /* [HGM] print nonexistent piece as its demoted version */
1503 piece = (ChessSquare) (DEMOTED piece);
1505 if(c=='+') *outp++ = c;
1506 *outp++ = ToUpper(PieceToChar(piece));
1508 if (cl.file || (cl.either && !cl.rank)) {
1514 else { *outp++ = (rf+ONE-'0')/10 + '0';*outp++ = (rf+ONE-'0')%10 + '0'; }
1517 if(board[rt][ft] != EmptySquare)
1523 else { *outp++ = (rt+ONE-'0')/10 + '0';*outp++ = (rt+ONE-'0')%10 + '0'; }
1524 if (gameInfo.variant == VariantShogi) {
1525 /* [HGM] in Shogi non-pawns can promote */
1526 *outp++ = promoChar; // Don't bother to correct move type, return value is never used!
1531 /* [HGM] Always long notation for fairies we don't know */
1536 case WhiteGrasshopper:
1537 case BlackGrasshopper:
1539 /* Moving a nonexistent piece */
1543 /* Not a legal move, even ignoring check.
1544 If there was a piece on the from square,
1545 use style "Ng1g3" or "Ng1xe8";
1546 if there was a pawn or nothing (!),
1547 use style "g1g3" or "g1xe8". Use "x"
1548 if a piece was on the to square, even
1549 a piece of the same color.
1552 if (piece != EmptySquare && piece != WhitePawn && piece != BlackPawn) {
1553 *outp++ = ToUpper(PieceToChar(piece));
1558 else { *outp++ = (rf+ONE-'0')/10 + '0';*outp++ = (rf+ONE-'0')%10 + '0'; }
1559 if (board[rt][ft] != EmptySquare) *outp++ = 'x';
1563 else { *outp++ = (rt+ONE-'0')/10 + '0';*outp++ = (rt+ONE-'0')%10 + '0'; }
1564 /* Use promotion suffix style "=Q" */
1565 if (promoChar != NULLCHAR && promoChar != 'x') {
1567 *outp++ = ToUpper(promoChar);
1574 // [HGM] XQ: the following code serves to detect perpetual chasing (Asian rules)
1583 // I guess the following variables logically belong in the closure too, but I was too lazy and used globals
1585 int preyStackPointer, chaseStackPointer;
1588 char rf, ff, rt, ft;
1598 // there are three new callbacks for use with GenLegal: for adding captures, deleting them, and finding a recapture
1600 extern void AtacksCallback P((Board board, int flags, ChessMove kind,
1601 int rf, int ff, int rt, int ft,
1604 void AttacksCallback(board, flags, kind, rf, ff, rt, ft, closure)
1610 { // For adding captures that can lead to chase indictment to the chaseStack
1611 if(board[rt][ft] == EmptySquare) return; // non-capture
1612 if(board[rt][ft] == WhitePawn && rt < BOARD_HEIGHT/2) return; // Pawn before river can be chased
1613 if(board[rt][ft] == BlackPawn && rt >= BOARD_HEIGHT/2) return; // Pawn before river can be chased
1614 if(board[rf][ff] == WhitePawn || board[rf][ff] == BlackPawn) return; // Pawns are allowed to chase
1615 if(board[rf][ff] == WhiteWazir || board[rf][ff] == BlackWazir) return; // King is allowed to chase
1616 // move cannot be excluded from being a chase trivially (based on attacker and victim); save it on chaseStack
1617 chaseStack[chaseStackPointer].rf = rf;
1618 chaseStack[chaseStackPointer].ff = ff;
1619 chaseStack[chaseStackPointer].rt = rt;
1620 chaseStack[chaseStackPointer].ft = ft;
1621 chaseStackPointer++;
1624 extern void ExistingAtacksCallback P((Board board, int flags, ChessMove kind,
1625 int rf, int ff, int rt, int ft,
1628 void ExistingAttacksCallback(board, flags, kind, rf, ff, rt, ft, closure)
1634 { // for removing pre-exsting captures from the chaseStack, to be left with newly created ones
1636 register ChaseClosure *cl = (ChaseClosure *) closure; //closure tells us the move played in the repeat loop
1638 if(board[rt][ft] == EmptySquare) return; // no capture
1639 if(rf == cl->rf && ff == cl->ff) { // attacks with same piece from new position are not considered new
1640 rf = cl->rt; ff = cl->ft; // doctor their fromSquare so they will be recognized in chaseStack
1642 // search move in chaseStack, and delete it if it occurred there (as we know now it is not a new capture)
1643 for(i=0; i<chaseStackPointer; i++) {
1644 if(chaseStack[i].rf == rf && chaseStack[i].ff == ff &&
1645 chaseStack[i].rt == rt && chaseStack[i].ft == ft ) {
1646 // move found on chaseStack, delete it by overwriting with move popped from top of chaseStack
1647 chaseStack[i] = chaseStack[--chaseStackPointer];
1653 extern void ProtectedCallback P((Board board, int flags, ChessMove kind,
1654 int rf, int ff, int rt, int ft,
1657 void ProtectedCallback(board, flags, kind, rf, ff, rt, ft, closure)
1663 { // for determining if a piece (given through the closure) is protected
1664 register ChaseClosure *cl = (ChaseClosure *) closure; // closure tells us where to recapture
1666 if(rt == cl->rt && ft == cl->ft) cl->recaptures++; // count legal recaptures to this square
1667 if(appData.debugMode && board[rt][ft] != EmptySquare)
1668 fprintf(debugFP, "try %c%c%c%c=%d\n", ff+AAA, rf+ONE,ft+AAA, rt+ONE, cl->recaptures);
1671 extern char moveList[MAX_MOVES][MOVE_LEN];
1673 int PerpetualChase(int first, int last)
1674 { // this routine detects if the side to move in the 'first' position is perpetually chasing (when not checking)
1677 ChessSquare captured;
1679 preyStackPointer = 0; // clear stack of chased pieces
1680 for(i=first; i<last; i+=2) { // for all positions with same side to move
1681 if(appData.debugMode) fprintf(debugFP, "judge position %i\n", i);
1682 chaseStackPointer = 0; // clear stack that is going to hold possible chases
1683 // determine all captures possible after the move, and put them on chaseStack
1684 GenLegal(boards[i+1], PosFlags(i), AttacksCallback, &cl);
1685 if(appData.debugMode) { int n;
1686 for(n=0; n<chaseStackPointer; n++)
1687 fprintf(debugFP, "%c%c%c%c ", chaseStack[n].ff+AAA, chaseStack[n].rf+ONE,
1688 chaseStack[n].ft+AAA, chaseStack[n].rt+ONE);
1689 fprintf(debugFP, ": all capts\n");
1691 // determine all captures possible before the move, and delete them from chaseStack
1692 cl.rf = moveList[i][1]-ONE; // prepare closure to pass move that led from i to i+1
1693 cl.ff = moveList[i][0]-AAA+BOARD_LEFT;
1694 cl.rt = moveList[i][3]-ONE;
1695 cl.ft = moveList[i][2]-AAA+BOARD_LEFT;
1696 GenLegal(boards[i], PosFlags(i), ExistingAttacksCallback, &cl);
1697 if(appData.debugMode) { int n;
1698 for(n=0; n<chaseStackPointer; n++)
1699 fprintf(debugFP, "%c%c%c%c ", chaseStack[n].ff+AAA, chaseStack[n].rf+ONE,
1700 chaseStack[n].ft+AAA, chaseStack[n].rt+ONE);
1701 fprintf(debugFP, ": new capts after %c%c%c%c\n", cl.ff+AAA, cl.rf+ONE, cl.ft+AAA, cl.rt+ONE);
1703 // chaseSack now contains all captures made possible by the move
1704 for(j=0; j<chaseStackPointer; j++) { // run through chaseStack to identify true chases
1705 int attacker = (int)boards[i+1][chaseStack[j].rf][chaseStack[j].ff];
1706 int victim = (int)boards[i+1][chaseStack[j].rt][chaseStack[j].ft];
1708 if(attacker >= (int) BlackPawn) attacker = BLACK_TO_WHITE attacker; // convert to white, as piecee type
1709 if(victim >= (int) BlackPawn) victim = BLACK_TO_WHITE victim;
1711 if((attacker == WhiteKnight || attacker == WhiteCannon) && victim == WhiteRook)
1712 continue; // C or H attack on R is always chase; leave on chaseStack
1714 if(attacker == victim) {
1715 if(LegalityTest(boards[i+1], PosFlags(i+1), chaseStack[j].rt,
1716 chaseStack[j].ft, chaseStack[j].rf, chaseStack[j].ff, NULLCHAR) == NormalMove) {
1717 // we can capture back with equal piece, so this is no chase but a sacrifice
1718 chaseStack[j] = chaseStack[--chaseStackPointer]; // delete the capture from the chaseStack
1719 j--; /* ! */ continue;
1724 // the attack is on a lower piece, or on a pinned or blocked equal one
1725 // test if the victim is protected by a true protector. First make the capture.
1726 captured = boards[i+1][chaseStack[j].rt][chaseStack[j].ft];
1727 boards[i+1][chaseStack[j].rt][chaseStack[j].ft] = boards[i+1][chaseStack[j].rf][chaseStack[j].ff];
1728 boards[i+1][chaseStack[j].rf][chaseStack[j].ff] = EmptySquare;
1729 // Then test if the opponent can recapture
1730 cl.recaptures = 0; // prepare closure to pass recapture square and count moves to it
1731 cl.rt = chaseStack[j].rt;
1732 cl.ft = chaseStack[j].ft;
1733 if(appData.debugMode) {
1734 fprintf(debugFP, "test if we can recapture %c%c\n", cl.ft+AAA, cl.rt+ONE);
1736 GenLegal(boards[i+1], PosFlags(i+1), ProtectedCallback, &cl); // try all moves
1737 // unmake the capture
1738 boards[i+1][chaseStack[j].rf][chaseStack[j].ff] = boards[i+1][chaseStack[j].rt][chaseStack[j].ft];
1739 boards[i+1][chaseStack[j].rt][chaseStack[j].ft] = captured;
1740 // if a recapture was found, piece is protected, and we are not chasing it.
1741 if(cl.recaptures) { // attacked piece was defended by true protector, no chase
1742 chaseStack[j] = chaseStack[--chaseStackPointer]; // so delete from chaseStack
1746 // chaseStack now contains all moves that chased
1747 if(appData.debugMode) { int n;
1748 for(n=0; n<chaseStackPointer; n++)
1749 fprintf(debugFP, "%c%c%c%c ", chaseStack[n].ff+AAA, chaseStack[n].rf+ONE,
1750 chaseStack[n].ft+AAA, chaseStack[n].rt+ONE);
1751 fprintf(debugFP, ": chases\n");
1753 if(i == first) { // copy all people chased by first move of repeat cycle to preyStack
1754 for(j=0; j<chaseStackPointer; j++) {
1755 preyStack[j].rank = chaseStack[j].rt;
1756 preyStack[j].file = chaseStack[j].ft;
1758 preyStackPointer = chaseStackPointer;
1761 for(j=0; j<chaseStackPointer; j++) {
1762 for(k=0; k<preyStackPointer; k++) {
1763 // search the victim of each chase move on the preyStack (first occurrence)
1764 if(chaseStack[j].ft == preyStack[k].file && chaseStack[j].rt == preyStack[k].rank ) {
1765 if(k < tail) break; // piece was already identified as still being chased
1766 preyStack[preyStackPointer] = preyStack[tail]; // move chased piece to bottom part of preyStack
1767 preyStack[tail] = preyStack[k]; // by swapping
1768 preyStack[k] = preyStack[preyStackPointer];
1774 preyStackPointer = tail; // keep bottom part of preyStack, popping pieces unchased on move i.
1775 if(appData.debugMode) { int n;
1776 for(n=0; n<preyStackPointer; n++)
1777 fprintf(debugFP, "%c%c ", preyStack[n].file+AAA, preyStack[n].rank+ONE);
1778 fprintf(debugFP, "always chased upto ply %d\n", i);
1780 // now adjust the location of the chased pieces according to opponent move
1781 for(j=0; j<preyStackPointer; j++) {
1782 if(preyStack[j].rank == moveList[i+1][1]-ONE &&
1783 preyStack[j].file == moveList[i+1][0]-AAA+BOARD_LEFT) {
1784 preyStack[j].rank = moveList[i+1][3]-ONE;
1785 preyStack[j].file = moveList[i+1][2]-AAA+BOARD_LEFT;
1790 return preyStackPointer; // if any piece was left on preyStack, it has been perpetually chased