feat: king check checker
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1e38040270
commit
4a2f3b5830
208
src/movegen.rs
208
src/movegen.rs
@ -8,7 +8,7 @@ use std::rc::Rc;
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/// Game tree node.
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#[derive(Clone, Debug)]
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struct Node {
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pub struct Node {
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/// Immutable position data.
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pos: BoardState,
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/// Backlink to previous node.
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@ -24,6 +24,18 @@ impl Default for Node {
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}
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}
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impl Node {
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/// Undo move.
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///
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/// Intended usage is to always keep an Rc to the current node, and overwrite it with the
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/// result of unmake.
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pub fn unmake(&self) -> Rc<Node> {
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self.prev
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.clone()
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.expect("unmake should not be called on root node")
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}
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}
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/// Piece enum specifically for promotions.
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#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
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enum PromotePiece {
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@ -66,10 +78,10 @@ impl Move {
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///
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/// Old position is saved in a backlink.
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/// No checking is done to verify even pseudo-legality of the move.
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pub fn make(self, old_node: Node) -> Node {
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pub fn make(self, old_node: Rc<Node>) -> Node {
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let old_pos = old_node.pos;
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let mut node = Node {
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prev: Some(Rc::new(old_node)),
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prev: Some(old_node),
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pos: old_pos,
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};
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@ -540,6 +552,75 @@ pub trait LegalMoveGen {
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fn gen_moves(&self) -> impl IntoIterator<Item = Move>;
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}
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/// Is a given player in check?
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fn is_check(board: &BoardState, pl: Color) -> bool {
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for src in board.pl(pl).board(Piece::King).into_iter() {
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macro_rules! detect_checker {
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($dirs: ident, $pc: ident, $keep_going: expr) => {
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for dir in $dirs.into_iter() {
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let (mut r, mut c) = src.to_row_col_signed();
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loop {
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let (nr, nc) = (r + dir.0, c + dir.1);
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if let Ok(sq) = Square::from_row_col_signed(nr, nc) {
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if let Some(pc) = board.get_piece(sq) {
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if pc.pc == Piece::$pc && pc.col != pl {
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return true;
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} else {
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break;
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}
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}
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} else {
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break;
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}
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if (!($keep_going)) {
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break;
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}
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r = nr;
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c = nc;
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}
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}
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};
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}
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let dirs_white_pawn = [(-1, 1), (-1, -1)];
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let dirs_black_pawn = [(1, 1), (1, -1)];
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detect_checker!(DIRS_STAR, Queen, true);
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detect_checker!(DIRS_DIAG, Bishop, true);
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detect_checker!(DIRS_STRAIGHT, Rook, true);
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detect_checker!(DIRS_STAR, King, false);
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detect_checker!(DIRS_KNIGHT, Knight, false);
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match pl {
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Color::White => detect_checker!(dirs_black_pawn, Pawn, false),
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Color::Black => detect_checker!(dirs_white_pawn, Pawn, false),
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}
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}
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false
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}
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impl LegalMoveGen for Node {
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fn gen_moves(&self) -> impl IntoIterator<Item = Move> {
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self.pos
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.gen_pseudo_moves()
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.into_iter()
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.filter(|mv| {
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// disallow friendly fire
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let src_pc = self
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.pos
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.get_piece(mv.src)
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.expect("move source should have piece");
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if let Some(dest_pc) = self.pos.get_piece(mv.dest) {
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return dest_pc.col != src_pc.col;
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}
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true
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})
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.filter(|mv| {
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// disallow moving into check
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let new_node = mv.make(self.clone().into());
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!is_check(&new_node.pos, self.pos.turn)
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})
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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@ -801,6 +882,116 @@ mod tests {
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}
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}
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/// Test check checker.
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#[test]
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fn test_is_check() {
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let check_cases = [
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"3r4/8/8/3K4/8/8/8/8 b - - 0 1",
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"8/8/8/3K3r/8/8/8/8 b - - 0 1",
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"8/8/8/3K4/8/8/8/3r4 b - - 0 1",
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"8/8/8/r2K4/8/8/8/8 b - - 0 1",
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"1b6/8/8/3K4/1r6/8/8/k6b b - - 0 1",
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"1b6/8/4p3/3K4/1r6/8/8/k5b1 b - - 0 1",
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"1b6/4n3/3p4/3K4/1r6/8/8/k5b1 b - - 0 1",
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"1b6/2n5/3p4/3K4/1r6/8/8/k5b1 b - - 0 1",
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"1b6/8/3p4/3K4/1r3n2/8/8/k5b1 b - - 0 1",
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"1b6/8/3p4/3K4/1r1k4/5n2/8/6b1 b - - 0 1",
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"8/8/8/4b3/r2b4/rnq5/PP6/KRrr4 w - - 0 1",
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]
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.map(|tc| (tc, true));
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let not_check_cases = [
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"1b6/8/3p4/3K4/1r6/5n2/8/k5b1 b - - 0 1",
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"1bqnb3/3q1n2/3p4/3K4/1r6/2q1qn2/8/k5b1 b - - 0 1",
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"1bqnb1q1/3q1n2/3p4/1qbKp1q1/1r1b4/2q1qn2/8/k5b1 b - - 0 1",
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"8/8/8/4b3/r2b4/r1q5/PP6/KRrr4 w - - 0 1",
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]
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.map(|tc| (tc, false));
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let all_cases = check_cases.iter().chain(¬_check_cases);
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for (fen, expected) in all_cases {
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let board = BoardState::from_fen(fen).unwrap();
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assert_eq!(
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is_check(&board, Color::White),
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*expected,
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"failed on {}",
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fen
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);
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}
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}
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/// Test legal movegen through contrived positions.
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#[test]
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fn test_legal_movegen() {
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let test_cases = [
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// rook friendly fire test
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(
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// start position
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"8/8/8/8/8/8/rr6/RRr5 w - - 0 1",
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// expected moves
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vec![
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(
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// source piece
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"a1",
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// destination squares
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vec!["a2"],
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MoveType::Normal,
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),
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(
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// source piece
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"b1",
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// destination squares
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vec!["b2", "c1"],
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MoveType::Normal,
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),
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],
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),
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// check test
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(
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"1bqnb1q1/3q1n2/q2p4/2bKp1q1/1r1b4/1q3n2/8/k2q2b1 w - - 0 1",
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vec![("d5", vec!["e4"], MoveType::Normal)],
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),
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// check test
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(
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"1b1nb1q1/q2q1n2/q2p4/2bKp1q1/1r1p4/1q3n2/8/k2q2b1 w - - 0 1",
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vec![("d5", vec!["e4"], MoveType::Normal)],
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),
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];
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for (i, (fen, expected)) in test_cases.iter().enumerate() {
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let node = Node {
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pos: BoardState::from_fen(fen).unwrap(),
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prev: None,
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};
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let mut moves: Vec<Move> = node.gen_moves().into_iter().collect();
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moves.sort_unstable();
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let moves = moves;
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let mut expected_moves = expected
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.iter()
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.map(|(src, dests, move_type)| {
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let src = src.parse::<Square>().unwrap();
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let dests = dests
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.iter()
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.map(|x| x.parse::<Square>())
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.map(|x| x.unwrap());
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dests.map(move |dest| Move {
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src,
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dest,
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move_type: *move_type,
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})
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})
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.flatten()
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.collect::<Vec<Move>>();
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expected_moves.sort_unstable();
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let expected_moves = expected_moves;
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assert_eq!(moves, expected_moves, "failed test case {i} ({fen})");
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}
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}
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/// Test that make move and unmake move work as expected.
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///
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/// Ensure that:
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@ -915,25 +1106,24 @@ mod tests {
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// make move
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eprintln!("Starting test case {i}, make move.");
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let mut node = Node {
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let mut node = Rc::new(Node {
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pos: BoardState::from_fen(start_pos).unwrap(),
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prev: None,
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};
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});
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for (move_str, expect_fen) in moves {
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let mv = Move::from_uci_algebraic(move_str).unwrap();
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eprintln!("Moving {move_str}.");
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node = mv.make(node);
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node = mv.make(node).into();
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assert_eq!(node.pos.to_fen(), expect_fen.to_string())
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}
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// unmake move
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eprintln!("Starting test case {i}, unmake move.");
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let mut cur_node = Rc::new(node.clone());
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for (_, expect_fen) in moves.iter().rev().chain([("", *start_pos)].iter()) {
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eprintln!("{}", expect_fen);
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assert_eq!(*cur_node.pos.to_fen(), expect_fen.to_string());
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assert_eq!(*node.pos.to_fen(), expect_fen.to_string());
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if *expect_fen != *start_pos {
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cur_node = cur_node.prev.clone().unwrap();
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node = node.unmake();
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}
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}
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}
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