Fix a subtle bug in Position::move_is_capture()

Currently fails if we test with a move that is not of from the side to move but from the opponent. This is the typical case of the threat from null move search. The result is an erroneus prune of the defending moves, see PruneDefendingMoves in ok_to_prune() Fix the test to work also with threat moves. Bug was always in but was unhidden by a patch of 17/12/2008 "Trigger of PawnEndgameExtension if capture is not a pawn" Until then it was hidden by a tricky check in the prune conditions instead of the natural move_is_capture() Signed-off-by: Marco Costalba <mcostalba@gmail.com>
mcostalba · Feb 13, 2009 · 52ed0e9 · 52ed0e9
1 parent 30e8f0c
commit 52ed0e9
Showing 1 changed file with 1 addition and 1 deletion.
diff --git a/src/position.cpp b/src/position.cpp
@@ -665,7 +665,7 @@ bool Position::move_is_capture(Move m) const {
   assert(m != MOVE_NONE);
 
   return (   !square_is_empty(move_to(m))
-          && (color_of_piece_on(move_to(m)) == opposite_color(side_to_move()))
+          && (color_of_piece_on(move_to(m)) != color_of_piece_on(move_from(m)))
          )
          || move_is_ep(m);
 }