Implement XBetza iso modifier

An 'i' modifier on a continuation leg will force it to be of equal length
(measured in steps) as the latest sliding leg (i.e. of maximum length != 1)
before it. This is useful for defining rifle captures of sliding pieces.
On initial legs it still means the move is for virgin pieces only.

diff --git a/moves.c b/moves.c
index 843593d..e6e316a 100644 (file)
--- a/moves.c
+++ b/moves.c
@@ -310,7 +310,7 @@ OK (Board board, int flags, ChessMove kind, int rf, int ff, int rt, int ft, VOID
 }
 
 void
-MovesFromString (Board board, int flags, int f, int r, int tx, int ty, int angle, char *desc, MoveCallback cb, VOIDSTAR cl)
+MovesFromString (Board board, int flags, int f, int r, int tx, int ty, int angle, int range, char *desc, MoveCallback cb, VOIDSTAR cl)
 {
     char buf[80], *p = desc, *atom = NULL;
     int mine, his, dir, bit, occup, i, ep, promoRank = -1;
@@ -407,10 +407,13 @@ MovesFromString (Board board, int flags, int f, int r, int tx, int ty, int angle
        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 == 2) { if(board[r][f] != initialPosition[r-2*his+3][f]) continue; } else
-       if(initial && (board[r][f] != initialPosition[r][f] ||
+       if(initial == 2) { if(board[r][f] != initialPosition[r-2*his+3][f]) continue; initial = 0; } else
+       if(initial && !range) {
+               if(   (board[r][f] != initialPosition[r][f] ||
                       r == 0              && board[TOUCHED_W] & 1<<f ||
-                      r == BOARD_HEIGHT-1 && board[TOUCHED_B] & 1<<f   ) ) continue;
+                      r == BOARD_HEIGHT-1 && board[TOUCHED_B] & 1<<f   )) continue;
+               initial = 0;
+       }
        if(expo > 0 && dx == 0 && dy == 0) {          // castling indicated by O + number
            mode |= 1024; dy = 1;
        }
@@ -453,23 +456,25 @@ MovesFromString (Board board, int flags, int f, int r, int tx, int ty, int angle
                if(board[y][x] < BlackPawn)   occup = 0x101; else
                if(board[y][x] < EmptySquare) occup = 0x102; else
                                              occup = 4;
+               if(initial && expo - i + 1 != range) { if(occup == 4) continue; else break; }
                if(cont) {                            // non-final leg
                  if(mode&16 && his&occup) occup &= 3;// suppress hopping foe in t-mode
                  if(occup & mode) {                  // valid intermediate square, do continuation
                    char origAtom = *atom;
+                   int rg = (expo != 1 ? expo - i + 1 : range);   // pass length of last *slider* leg
                    if(!(bit & all)) *atom = rotate[*atom - 'A']; // orth-diag interconversion to make direction valid
                    if(occup & mode & 0x104)          // no side effects, merge legs to one move
-                       MovesFromString(board, flags, f, r, x, y, dir, cont, cb, cl);
+                       MovesFromString(board, flags, f, r, x, y, dir, rg, cont, cb, cl);
                    if(occup & mode & 3 && (killX < 0 || kill2X < 0 && (legNr > 1 || killX == x && killY == y) ||
                                            (legNr == 1 ? kill2X == x && kill2Y == y : killX == x && killY == y))) {     // destructive first leg
                        int cnt = 0;
                        legNr <<= 1;
-                       MovesFromString(board, flags, f, r, x, y, dir, cont, &OK, &cnt);  // count possible continuations
+                       MovesFromString(board, flags, f, r, x, y, dir, rg, cont, &OK, &cnt); // count possible continuations
                        legNr >>= 1;
-                       if(cnt) {                                                         // and if there are
+                       if(cnt) {                                                            // and if there are
                            if(legNr & 1 ? killX < 0 : kill2X < 0) cb(board, flags, FirstLeg, r, f, y, x, cl);     // then generate their first leg
                            legNr <<= 1;
-                           MovesFromString(board, flags, f, r, x, y, dir, cont, cb, cl);
+                           MovesFromString(board, flags, f, r, x, y, dir, rg, cont, cb, cl);
                            legNr >>= 1;
                        }
                    }
@@ -751,7 +756,7 @@ GenPseudoLegal (Board board, int flags, MoveCallback callback, VOIDSTAR closure,
                  piece = (ChessSquare) ( DEMOTED(piece) );
           if(filter != EmptySquare && piece != filter) continue;
           if(pieceDefs && pieceDesc[piece]) { // [HGM] gen: use engine-defined moves
-              MovesFromString(board, flags, ff, rf, -1, -1, 0, pieceDesc[piece], callback, closure);
+              MovesFromString(board, flags, ff, rf, -1, -1, 0, 0, pieceDesc[piece], callback, closure);
               continue;
           }
           if(IS_SHOGI(gameInfo.variant))