From: H.G. Muller <h.g.muller@hccnet.nl>
Date: Thu, 16 Sep 2010 16:48:29 +0000 (+0200)
Subject: Extend legality testing to drop moves
X-Git-Url: http://winboard.nl/cgi-bin?a=commitdiff_plain;h=7d36b24250db61fe2fd46465d7685ce008f7d546;p=xboard.git

Extend legality testing to drop moves

LegalityTest() can nowbe called with (internal-format) drop moves, and
delegates their testing to a new routine LegalDrop(). This routine
performs the 'no-pawn-on-back-rank' test that used to be in
UserMoveTest (which now calls LegalityTest also for drop moves).
The more complex Shogi case is also handled (except for Pawn mate
drops) in LegalDrop().
---

diff --git a/backend.c b/backend.c
index 65ea20d..12cef35 100644
--- a/backend.c
+++ b/backend.c
@@ -895,7 +895,7 @@ InitBackEnd1()
       case VariantGothic:     /* [HGM] should work */
       case VariantCapablanca: /* [HGM] should work */
       case VariantCourier:    /* [HGM] initial forced moves not implemented */
-      case VariantShogi:      /* [HGM] drops not tested for legality */
+      case VariantShogi:      /* [HGM] could still mate with pawn drop */
       case VariantKnightmate: /* [HGM] should work */
       case VariantCylinder:   /* [HGM] untested */
       case VariantFalcon:     /* [HGM] untested */
@@ -5996,7 +5996,7 @@ UserMoveEvent(fromX, fromY, toX, toY, promoChar)
 	   fromX = fromX ? WhitePawn : BlackPawn; // first piece type in selected holdings
 	   while(PieceToChar(fromX) == '.' || PieceToNumber(fromX) != fromY && fromX != (int) EmptySquare) fromX++; 
          fromY = DROP_RANK;
-    } else
+    }
 
     /* [HGM] always test for legality, to get promotion info */
     moveType = LegalityTest(boards[currentMove], PosFlags(currentMove),
@@ -7164,9 +7164,7 @@ FakeBookMove: // [HGM] book: we jump here to simulate machine moves after book h
         /* to make sure an illegal e.p. capture does not slip through,   */
         /* to cause a forfeit on a justified illegal-move complaint      */
         /* of the opponent.                                              */
-        if( gameMode==TwoMachinesPlay && appData.testLegality
-            && fromY != DROP_RANK /* [HGM] temporary; should still add legality test for drops */
-                                                              ) {
+        if( gameMode==TwoMachinesPlay && appData.testLegality ) {
            ChessMove moveType;
            moveType = LegalityTest(boards[forwardMostMove], PosFlags(forwardMostMove),
                              fromY, fromX, toY, toX, promoChar);
diff --git a/moves.c b/moves.c
index 545a09c..f4f33b2 100644
--- a/moves.c
+++ b/moves.c
@@ -987,7 +987,7 @@ int CheckTest(board, flags, rf, ff, rt, ft, enPassant)
 	}
 	board[rt][ft] = board[rf][ff];
 	board[rf][ff] = EmptySquare;
-    }
+    } else board[rt][ft] = ff; // [HGM] drop
 
     /* For compatibility with ICS wild 9, we scan the board in the
        order a1, a2, a3, ... b1, b2, ..., h8 to find the first king,
@@ -1022,11 +1022,44 @@ int CheckTest(board, flags, rf, ff, rt, ft, enPassant)
 	} else {
 	    board[rt][ft] = captured;
 	}
-    }
+    } else board[rt][ft] = EmptySquare; // [HGM] drop
 
     return cl.fking < BOARD_RGHT ? cl.check : 1000; // [HGM] atomic: return 1000 if we have no king
 }
 
+ChessMove LegalDrop(board, flags, piece, rt, ft)
+     Board board;
+     int flags;
+     ChessSquare piece;
+     int rt, ft;
+{   // [HGM] put drop legality testing in separate routine for clarity
+    int n;
+if(appData.debugMode) fprintf(debugFP, "LegalDrop: %d @ %d,%d)\n", piece, ft, rt);
+    if(board[rt][ft] != EmptySquare) return ImpossibleMove; // must drop to empty square
+    n = PieceToNumber(piece);
+    if(gameInfo.holdingsWidth == 0 || (flags & F_WHITE_ON_MOVE ? board[n][BOARD_WIDTH-1] : board[BOARD_HEIGHT-1-n][0]) != piece)
+        return ImpossibleMove; // piece not available
+    if(gameInfo.variant == VariantShogi) { // in Shogi lots of drops are forbidden!
+        if((piece == WhitePawn || piece == WhiteQueen) && rt == BOARD_HEIGHT-1 ||
+           (piece == BlackPawn || piece == BlackQueen) && rt == 0 ||
+            piece == WhiteKnight && rt > BOARD_HEIGHT-3 ||
+            piece == BlackKnight && rt < 2 ) return IllegalMove; // e.g. where dropped piece has no moves
+        if(piece == WhitePawn || piece == BlackPawn) {
+            int r;
+            for(r=1; r<BOARD_HEIGHT-1; r++)
+                if(board[r][ft] == piece) return IllegalMove; // or there already is a Pawn in file
+            // should still test if we mate with this Pawn
+        }
+    } else {
+        if( (piece == WhitePawn || piece == BlackPawn) &&
+            (rt == 0 || rt == BOARD_HEIGHT -1 ) )
+            return IllegalMove; /* no pawn drops on 1st/8th */
+    }
+if(appData.debugMode) fprintf(debugFP, "LegalDrop: %d @ %d,%d)\n", piece, ft, rt);
+    if (!(flags & F_IGNORE_CHECK) &&
+	CheckTest(board, flags, DROP_RANK, piece, rt, ft, FALSE) ) return IllegalMove;
+    return flags & F_WHITE_ON_MOVE ? WhiteDrop : BlackDrop;
+}
 
 extern void LegalityTestCallback P((Board board, int flags, ChessMove kind,
 				    int rf, int ff, int rt, int ft,
@@ -1055,7 +1088,10 @@ ChessMove LegalityTest(board, flags, rf, ff, rt, ft, promoChar)
      int flags;
      int rf, ff, rt, ft, promoChar;
 {
-    LegalityTestClosure cl; ChessSquare piece = board[rf][ff], *castlingRights = board[CASTLING];
+    LegalityTestClosure cl; ChessSquare piece, *castlingRights = board[CASTLING];
+
+    if(rf == DROP_RANK) return LegalDrop(board, flags, ff, rt, ft);
+    piece = board[rf][ff];
     
     if (appData.debugMode) {
         int i;
diff --git a/parser.c b/parser.c
index ee1e2b1..ca1681b 100644
--- a/parser.c
+++ b/parser.c
@@ -2838,7 +2838,7 @@ case 11:
 YY_RULE_SETUP
 #line 826 "parser.l"
 {
-    /* Bughouse piece drop.  No legality checking for now. */
+    /* Bughouse piece drop. */
     currentMoveString[1] = '@';
     currentMoveString[2] = yytext[2];
     currentMoveString[3] = yytext[3];
@@ -2854,11 +2854,11 @@ YY_RULE_SETUP
 
     if (WhiteOnMove(yyboardindex)) {
 	currentMoveString[0] = ToUpper(yytext[0]);
-	return (int) WhiteDrop;
     } else {
 	currentMoveString[0] = ToLower(yytext[0]);
-	return (int) BlackDrop;
     }
+    return LegalityTest(boards[yyboardindex], PosFlags(yyboardindex), DROP_RANK, // [HGM] does drops now too
+                        CharToPiece(currentMoveString[0]), currentMoveString[3] - ONE, currentMoveString[2] - AAA, NULLCHAR);
 }
 	YY_BREAK
 case 12:
diff --git a/parser.l b/parser.l
index 528b3de..9590fe2 100644
--- a/parser.l
+++ b/parser.l
@@ -824,7 +824,7 @@ extern void CopyBoard P((Board to, Board from));
 }
 
 [A-Z][@*][a-l][0-9] {
-    /* Bughouse piece drop.  No legality checking for now. */
+    /* Bughouse piece drop. */
     currentMoveString[1] = '@';
     currentMoveString[2] = yytext[2];
     currentMoveString[3] = yytext[3];
@@ -840,11 +840,11 @@ extern void CopyBoard P((Board to, Board from));
 
     if (WhiteOnMove(yyboardindex)) {
 	currentMoveString[0] = ToUpper(yytext[0]);
-	return (int) WhiteDrop;
     } else {
 	currentMoveString[0] = ToLower(yytext[0]);
-	return (int) BlackDrop;
     }
+    return LegalityTest(boards[yyboardindex], PosFlags(yyboardindex), DROP_RANK, // [HGM] does drops now too
+                        CharToPiece(currentMoveString[0]), currentMoveString[3] - ONE, currentMoveString[2] - AAA, NULLCHAR);
 }
 
 [Rr]esign(s|ed)?  {