From 500e6fd22f196c7df5998636929cc6ad78a22224 Mon Sep 17 00:00:00 2001 From: Bruno BELANYI Date: Wed, 20 Jul 2022 18:48:22 +0200 Subject: [PATCH] Add 'Color::slide_board_with_blockers' --- src/board/direction.rs | 42 +++++++++++++++++++++++++++++++++++++++++- 1 file changed, 41 insertions(+), 1 deletion(-) diff --git a/src/board/direction.rs b/src/board/direction.rs index 135f5f4..cfed3cb 100644 --- a/src/board/direction.rs +++ b/src/board/direction.rs @@ -121,7 +121,19 @@ impl Direction { /// It does not make sense to use this method with knight-only directions, and it will panic in /// debug-mode if it happens. #[inline(always)] - pub fn slide_board(self, mut board: Bitboard) -> Bitboard { + pub fn slide_board(self, board: Bitboard) -> Bitboard { + self.slide_board_with_blockers(board, Bitboard::EMPTY) + } + + /// Slide a board along the given [Direction], i.e: return all successive applications of + /// [Direction::move_board] until no new squares can be reached. + /// Take into account the `blockers` [Bitboard]: a combination of all pieces on the board which + /// cannot be slided over. The slide is over once a square that is part of `blockers` is + /// reached. + /// It does not make sense to use this method with knight-only directions, and it will panic in + /// debug-mode if it happens. + #[inline(always)] + pub fn slide_board_with_blockers(self, mut board: Bitboard, blockers: Bitboard) -> Bitboard { debug_assert!(!Self::KNIGHT_DIRECTIONS.contains(&self)); let mut res = Default::default(); @@ -129,6 +141,9 @@ impl Direction { while !board.is_empty() { board = self.move_board(board); res = res | board; + if !(board & blockers).is_empty() { + break; + } } res @@ -655,4 +670,29 @@ mod test { Bitboard::DIAGONAL - Square::A1 ); } + + #[test] + fn blocked_slides() { + assert_eq!( + Direction::North + .slide_board_with_blockers(Square::A1.into_bitboard(), Square::A2.into_bitboard()), + Square::A2.into_bitboard() + ); + assert_eq!( + Direction::North + .slide_board_with_blockers(Square::A1.into_bitboard(), Square::A3.into_bitboard()), + Square::A2 | Square::A3 + ); + assert_eq!( + Direction::North + .slide_board_with_blockers(Square::A1.into_bitboard(), Square::A4.into_bitboard()), + Square::A2 | Square::A3 | Square::A4 + ); + // Ensure that the starting square being in `blockers` is not an issue + assert_eq!( + Direction::North + .slide_board_with_blockers(Square::A1.into_bitboard(), Square::A1.into_bitboard()), + File::A.into_bitboard() - Square::A1 + ); + } }