tom@tnosoes.UUCP (Tom Vijlbrief) (01/23/90)
The routine Undo() in gnuchess 1.52 (I don't have the newer version 1.55)
does not correctly undo a pawn promotion. Undo() is in nondsp.c and uxdsp.c.
The original version is:
======================================================================
Undo()
/*
Undo the most recent half-move.
*/
{
short f,t;
f = GameList[GameCnt].gmove>>8;
t = GameList[GameCnt].gmove & 0xFF;
if (board[t] == king && distance(t,f) > 1)
castle(GameList[GameCnt].color,f,t,2);
else
{
board[f] = board[t]; color[f] = color[t];
board[t] = GameList[GameCnt].piece;
color[t] = GameList[GameCnt].color;
if (board[f] == king) --kingmoved[color[f]];
}
if (TCflag) ++TimeControl.moves[color[f]];
GameCnt--; mate = false; Sdepth = 0;
UpdateDisplay(0,0,1,0);
InitializeStats();
}
==================================================
The fixed version is:
=================================================
......
{
short f,t;
f = GameList[GameCnt].gmove>>8;
t = GameList[GameCnt].gmove & 0xFF;
if (board[t] == king && distance(t,f) > 1)
castle(GameList[GameCnt].color,f,t,2);
else
{
/* Check for promotion: */
if (board[t] == queen &&
((row[f]==6 && row[t]==7) || (row[f]==1 && row[t]==0))) {
int g, from= f;
for (g= GameCnt-1; g>=0; g--)
if (GameList[g].gmove & 0xFF == from)
from= GameList[g].gmove>>8;
if (row[from]==1 || row[from]==6)
board[t]= pawn;
}
board[f] = board[t]; color[f] = color[t];
board[t] = GameList[GameCnt].piece;
color[t] = GameList[GameCnt].color;
if (board[f] == king) --kingmoved[color[f]];
}
.... etc ....
======================================================
===============================================================================
Tom Vijlbrief
TNO Institute for Perception
P.O. Box 23 Phone: +31 34 63 562 11
3769 ZG Soesterberg E-mail: tnosoes!tom@mcvax.cwi.nl
The Netherlands or: uunet!mcvax!tnosoes!tom
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