Implement e.p. capture

For Chess and Mighty Lion e.p. capture was needed. This is controlled by
chessFlag, which also controlled the possibility to double-push M moves.
The e.p. captures are generated as two-leg moves over the victim Pawn,
after all other captures have been generated, and depending on promoSuppress,
which flags double-pushes, and is not used for other purposes in Chess
(where deferral is not possible, with Pawns promoting on last rank only).
When parsing input moves, e.p. capture is recognized, and expanded to
a two-leg move before searching it in the move list.

diff --git a/hachu.c b/hachu.c
index ce8ccc4..3367f3c 100644 (file)
--- a/hachu.c
+++ b/hachu.c
@@ -1242,6 +1242,8 @@ MakeMove(Move m, UndoInfo *u)
 \r
   if(p[u->piece].promoFlag & LAST_RANK) cnt50 = 0; // forward piece: move is irreversible\r
   // TODO: put in some test for forward moves of non-backward pieces?\r
+//             int n = board[promoSuppress-1];\r
+//             if( n != EMPTY && (n&TYPE) == xstm && p[n].value == 8 ) NewNonCapt(promoSuppress-1, 16, 0);\r
 \r
   if(p[u->piece].value == FVAL) { // move with Fire Demon\r
     int i, f=~fireFlags[u->piece-2];\r
@@ -1839,15 +1841,18 @@ if(PATH) printf("%d:%2d:%2d msp=%d\n",level,depth,iterDep,msp);
 if(PATH) printf("captures on %d generated, msp=%d, group=%d, threshold=%d\n", nextVictim, msp, group, threshold);\r
              goto extractMove; // in auto-fail phase, only search if they might auto-fail-hi\r
            }\r
+           if(chessFlag && promoSuppress != ABSENT) { // e.p. rights. Create e.p. captures as Lion moves\r
+               int n = board[promoSuppress-1], old = msp; // a-side neighbor of pushed pawn\r
+               if( n != EMPTY && (n&TYPE) == stm && p[n].value == 80 ) NewCapture(promoSuppress-1, SPECIAL + 20 - 4*stm, 0);\r
+               n = board[promoSuppress+1];      // h-side neighbor of pushed pawn\r
+               if( n != EMPTY && (n&TYPE) == stm && p[n].value == 80 ) NewCapture(promoSuppress+1, SPECIAL + 52 - 4*stm, 0);\r
+               if(msp != old) goto extractMove; // one or more e.p. capture were generated\r
+           }\r
 if(PATH) printf("# autofail=%d\n", autoFail);\r
            if(autoFail) { // non-captures cannot auto-fail; flush queued captures first\r
 if(PATH) printf("# autofail end (%d-%d)\n", firstMove, msp);\r
              autoFail = 0; curMove = firstMove - 1; continue; // release stashed moves for search\r
            }\r
-//         if(currentVariant == V_CHESS && promoSuppress != ABSENT) { // e.p.\r
-//             int n = board[promoSuppress-1];\r
-//             if( n != EMPTY && (n&TYPE) == xstm && p[n].value == 8 ) \r
-//         }\r
            phase = 4; // out of victims: all captures generated\r
          case 4: // dubious captures\r
 #if 0\r
@@ -2337,6 +2342,11 @@ ParseMove (char *moveText)
     for(j=0; j<8; j++) if(e + kStep[j] == t) break;\r
     if(j >= 8) return INVALID; // this rejects Lion Dog 1+2 moves!\r
     t2 = SPECIAL + 8*i + j;\r
+  } else if(chessFlag && board[f] != EMPTY && p[board[f]].value == 80 && board[t] == EMPTY) { // Pawn to empty, could be e.p.\r
+      if(t == f + BW + 1) t2 = SPECIAL + 16; else\r
+      if(t == f + BW - 1) t2 = SPECIAL + 48; else\r
+      if(t == f - BW + 1) t2 = SPECIAL + 20; else\r
+      if(t == f - BW - 1) t2 = SPECIAL + 52; // fake double-move\r
   }\r
   ret = f<<SQLEN | t2;\r
   if(*moveText != '\n' && *moveText != '=') ret |= PROMOTE;\r