# en passant
my $ep = "-";
if ($x[10] != -1) {
- $ep = (qw(a b c d e f g h))[$x[10]];
+ my $col = $x[10];
+ my $nep = (qw(a b c d e f g h))[$col];
+
+ if ($x[9] eq 'B') {
+ $nep .= "3";
+ } else {
+ $nep .= "6";
+ }
+
+ #
+ # Showing the en passant square when actually no capture can be made
+ # seems to confuse at least Rybka. Thus, check if there's actually
+ # a pawn of the opposite side that can do the en passant move, and if
+ # not, just lie -- it doesn't matter anyway. I'm unsure what's the
+ # "right" thing as per the standard, though.
+ #
if ($x[9] eq 'B') {
- $ep .= "3";
+ $ep = $nep if ($col > 0 && substr($board[4], $col-1, 1) eq 'p');
+ $ep = $nep if ($col < 7 && substr($board[4], $col+1, 1) eq 'p');
} else {
- $ep .= "6";
+ $ep = $nep if ($col > 0 && substr($board[3], $col-1, 1) eq 'P');
+ $ep = $nep if ($col < 7 && substr($board[3], $col+1, 1) eq 'P');
}
}
$fen .= " ";