From: H.G. Muller <h.g.muller@hccnet.nl>
Date: Mon, 11 Oct 2010 07:13:59 +0000 (+0200)
Subject: Test Legality of Shogi promotions
X-Git-Url: http://winboard.nl/cgi-bin?p=capablanca.git;a=commitdiff_plain;h=b0878c4bb13c5ba03f6defe11f903fa07247b718

Test Legality of Shogi promotions

The old code would allow any drop, except Pawns on first and last rank,
which is actually too restrictive for Shogi (which does allow back-rank
Pawn drops). Only thing still missing is Pawn drop with mate.
---

diff --git a/lasker-2.2.3/src/movecheck.c b/lasker-2.2.3/src/movecheck.c
index c0dd853..1f6d69b 100644
--- a/lasker-2.2.3/src/movecheck.c
+++ b/lasker-2.2.3/src/movecheck.c
@@ -1303,6 +1303,21 @@ int legal_move(struct game_state_t * gs,
       return 0;
     if (gs->board[tFile][tRank] != NOPIECE)
       return 0;
+    if (gs->promoType == 3) { // Shogi
+      int r;
+      switch(move_piece) {
+	case PAWN:  // check for own Pawn in same file
+	  for(r=0; r<gs->ranks; r++) if(gs->board[tFile][r] == (gs->onMove|PAWN)) return 0;
+	case LANCE: // Pawns and Lances not on last rank
+	  if(gs->onMove == WHITE && tRank >= gs->ranks-1) return 0;
+	  if(gs->onMove == BLACK && tRank < 1) return 0;
+	  break;
+	case HONORABLEHORSE: // Knights at least two ranks from edge
+	  if(gs->onMove == WHITE && tRank >= gs->ranks-2) return 0;
+	  if(gs->onMove == BLACK && tRank < 2) return 0;
+	default: ;
+      }
+    } else
     if (move_piece == PAWN && (tRank == 0 || tRank == gs->ranks-1))
       return 0;
     return 1;