Improve SAN of Pawn moves and allow Betza e.p. definition

The move descriptions in 'piece' commands can now use 'i' and 'n'
modifiers to define a blockable double push. ('n' only work for moves
of stride 2!) The test for initial moves now is based on comparison with
the opening position, rather than on a way-to-generous heuristic. (This
still does not prove in generak the piece did not move, though, but it
does for Pawns.) A new 'e' modifier stands for e.p. capture; to implement
this the rank and file of the e.p. square are now stored in the board.
(EP_STATUS was holding the file of the moved Pawn, which in Berolina Chess
is not the file of the e.p. square!)
 The generation of SAN moves for Pawns can now reliably distinguish between
captures and non-captures even in Berolina, when the move generator informs
it whether the move was e.p. capture.

diff --git a/backend.c b/backend.c
index 7f38a5d..6fac052 100644 (file)
--- a/backend.c
+++ b/backend.c
@@ -9882,6 +9882,7 @@ ApplyMove (int fromX, int fromY, int toX, int toY, int promoChar, Board board)
       if(gameInfo.variant == VariantBerolina) berolina = EP_BEROLIN_A;
       oldEP = (signed char)board[EP_STATUS];
       board[EP_STATUS] = EP_NONE;
+      board[EP_FILE] = board[EP_RANK] = 100;
 
   if (fromY == DROP_RANK) {
        /* must be first */
@@ -9916,6 +9917,7 @@ ApplyMove (int fromX, int fromY, int toX, int toY, int promoChar, Board board)
            if(fromY != toY) // [HGM] Xiangqi sideway Pawn moves should not count as 50-move breakers
               board[EP_STATUS] = EP_PAWN_MOVE;
            if( toY-fromY==2) {
+               board[EP_FILE] = (fromX + toX)/2; board[EP_RANK] = (fromY + toY)/2;
                if(toX>BOARD_LEFT   && board[toY][toX-1] == BlackPawn &&
                        gameInfo.variant != VariantBerolina || toX < fromX)
                      board[EP_STATUS] = toX | berolina;
@@ -9928,6 +9930,7 @@ ApplyMove (int fromX, int fromY, int toX, int toY, int promoChar, Board board)
            if(fromY != toY) // [HGM] Xiangqi sideway Pawn moves should not count as 50-move breakers
               board[EP_STATUS] = EP_PAWN_MOVE;
            if( toY-fromY== -2) {
+               board[EP_FILE] = (fromX + toX)/2; board[EP_RANK] = (fromY + toY)/2;
                if(toX>BOARD_LEFT   && board[toY][toX-1] == WhitePawn &&
                        gameInfo.variant != VariantBerolina || toX < fromX)
                      board[EP_STATUS] = toX | berolina;

diff --git a/common.h b/common.h
index 24b7ce0..86a9c5c 100644 (file)
--- a/common.h
+++ b/common.h
@@ -180,6 +180,8 @@ typedef char *String;
 #define BOARD_RGHT   (gameInfo.boardWidth + gameInfo.holdingsWidth)
 #define CASTLING     (BOARD_RANKS-1)           /* [HGM] hide in upper rank   */
 #define VIRGIN       (BOARD_RANKS-2)           /* [HGM] pieces not moved     */
+#define EP_RANK      CASTLING][(BOARD_FILES-4) /* [HGM] in upper rank        */
+#define EP_FILE      CASTLING][(BOARD_FILES-3) /* [HGM] in upper rank        */
 #define EP_STATUS    CASTLING][(BOARD_FILES-2) /* [HGM] in upper rank        */
 #define HOLDINGS_SET CASTLING][(BOARD_FILES-1) /* [HGM] in upper-right corner*/
 #define ONE          ('1'-(BOARD_HEIGHT==10))  /* [HGM] foremost board rank  */

diff --git a/moves.c b/moves.c
index f780f85..9700dbf 100644 (file)
--- a/moves.c
+++ b/moves.c
@@ -171,9 +171,9 @@ CompareBoards (Board board1, Board board2)
 // [HGM] gen: configurable move generation from Betza notation sent by engine.
 
 //  alphabet      "abcdefghijklmnopqrstuvwxyz"
-char symmetry[] = "FBNW.F.WFNKN.N..QR....W..N";
-char xStep[]    = "2110.1.03102.10.00....0..2";
-char yStep[]    = "2132.1.33313.20.11....1..3";
+char symmetry[] = "FBNW.FFW.NKN.NW.QR....W..N";
+char xStep[]    = "2110.130.102.10.00....0..2";
+char yStep[]    = "2132.133.313.20.11....1..3";
 char dirType[]  = "01000104000200000260050000";
 //  alphabet   "a b    c d e f    g h    i j k l    m n o p q r    s    t u v    w x y z "
 int dirs1[] = { 0,0x3C,0,0,0,0xC3,0,0,   0,0,0,0xF0,0,0,0,0,0,0x0F,0   ,0,0,0   ,0,0,0,0 };
@@ -197,8 +197,8 @@ MovesFromString (Board board, int flags, int f, int r, char *desc, MoveCallback
     int mine, his, dir, bit, occup, i;
     if(flags & F_WHITE_ON_MOVE) his = 2, mine = 1; else his = 1, mine = 2;
     while(*p) {                  // more moves to go
-       int expo = 1, dx, dy, x, y, mode, dirSet, retry=0, initial=0;
-       if(*p == 'i') initial = 1, p++;
+       int expo = 1, dx, dy, x, y, mode, dirSet, retry=0, initial=0, jump=1;
+       if(*p == 'i') initial = 1, desc = ++p;
        while(islower(*p)) p++;  // skip prefixes
        if(!isupper(*p)) return; // syntax error: no atom
        dirSet = 0;              // build direction set based on atom symmetry
@@ -246,25 +246,34 @@ MovesFromString (Board board, int flags, int f, int r, char *desc, MoveCallback
        if(*desc == 'm') mode |= 4, desc++;
        if(*desc == 'c') mode |= his, desc++;
        if(*desc == 'd') mode |= mine, desc++;
+       if(*desc == 'e') mode |= 8, desc++;
+       if(*desc == 'n') jump = 0, desc++;
+       while(*desc == 'j') jump++, desc++;
        if(!mode) mode = his + 4;// no mode spec, use default = mc
        dx = xStep[*p-'A'] - '0';                     // step vector of atom
        dy = yStep[*p-'A'] - '0';
        if(isdigit(*++p)) expo = atoi(p++);           // read exponent
        if(expo > 9) p++;                             // allow double-digit
        desc = p;                                     // this is start of next move
-       if(initial && (mine == 1 ? r > 1 : r < BOARD_HEIGHT - 2)) continue;
+       if(initial && board[r][f] != initialPosition[r][f]) continue;
         do {
          for(dir=0, bit=1; dir<8; dir++, bit += bit) { // loop over directions
-           int i = expo;
+           int i = expo, vx, vy;
            if(!(bit & dirSet)) continue;             // does not move in this direction
+           vx = dx*rot[dir][0] + dy*rot[dir][1];     // rotate step vector
+           vy = dx*rot[dir][2] + dy*rot[dir][3];
            x = f; y = r;                             // start square
            do {
-               x += dx*rot[dir][0] + dy*rot[dir][1]; // step to next square
-               y += dx*rot[dir][2] + dy*rot[dir][3];
+               x += vx; y += vy;                     // step to next square
                if(y < 0 || y >= BOARD_HEIGHT || x < BOARD_LEFT || x >= BOARD_RGHT) break;
+               if(!jump    && board[y - vy + vy/2][x - vx + vx/2] != EmptySquare) break; // blocked
+               if(jump > 1 && board[y - vy + vy/2][x - vx + vx/2] == EmptySquare) break; // no hop
                if(board[y][x] < BlackPawn)   occup = 1; else
                if(board[y][x] < EmptySquare) occup = 2; else
                                              occup = 4;
+               if(mode & 8 && y == board[EP_RANK] && occup == 4 && board[EP_FILE] == x) { // to e.p. square
+                   cb(board, flags, mine == 1 ? WhiteCapturesEnPassant : BlackCapturesEnPassant, r, f, y, x, cl);
+               }
                if(occup & mode) cb(board, flags, NormalMove, r, f, y, x, cl); // allowed, generate
                if(occup != 4) break; // not valid transit square
            } while(--i);
@@ -1979,7 +1988,7 @@ CoordsToAlgebraic (Board board, int flags, int rf, int ff, int rt, int ft, int p
 {
     ChessSquare piece;
     ChessMove kind;
-    char *outp = out, c;
+    char *outp = out, c, capture;
     CoordsToAlgebraicClosure cl;
 
     if (rf == DROP_RANK) {
@@ -2012,14 +2021,15 @@ CoordsToAlgebraic (Board board, int flags, int rf, int ff, int rt, int ft, int p
        }
        /* Pawn move */
         *outp++ = ff + AAA;
-        if (ff == ft && board[rt][ft] == EmptySquare) { /* [HGM] Xiangqi has straight noncapts! */
+       capture = board[rt][ft] != EmptySquare || kind == WhiteCapturesEnPassant || kind == BlackCapturesEnPassant;
+        if (ff == ft && !capture) { /* [HGM] Xiangqi has straight noncapts! */
            /* Non-capture; use style "e5" */
             if(rt+ONE <= '9')
                *outp++ = rt + ONE;
             else { *outp++ = (rt+ONE-'0')/10 + '0';*outp++ = (rt+ONE-'0')%10 + '0'; }
        } else {
            /* Capture; use style "exd5" */
-            if(gameInfo.variant != VariantXiangqi || board[rt][ft] != EmptySquare )
+            if(capture)
             *outp++ = 'x';  /* [HGM] Xiangqi has sideway noncaptures across river! */
             *outp++ = ft + AAA;
             if(rt+ONE <= '9')

diff --git a/moves.h b/moves.h
index 5579cbd..db6df14 100644 (file)
--- a/moves.h
+++ b/moves.h
@@ -62,6 +62,7 @@ extern int CompareBoards P((Board board1, Board board2));
 extern char pieceToChar[(int)EmptySquare+1];
 extern char pieceNickName[(int)EmptySquare];
 extern char *pieceDesc[(int)EmptySquare];
+extern Board initialPosition;
 
 typedef void (*MoveCallback) P((Board board, int flags, ChessMove kind,
                                int rf, int ff, int rt, int ft,