Trait shakmaty::Position

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pub trait Position {
Show 39 methods    // Required methods
    fn board(&self) -> &Board;
    fn promoted(&self) -> Bitboard;
    fn pockets(&self) -> Option<&ByColor<ByRole<u8>>>;
    fn turn(&self) -> Color;
    fn castles(&self) -> &Castles;
    fn maybe_ep_square(&self) -> Option<Square>;
    fn remaining_checks(&self) -> Option<&ByColor<RemainingChecks>>;
    fn halfmoves(&self) -> u32;
    fn fullmoves(&self) -> NonZeroU32;
    fn into_setup(self, mode: EnPassantMode) -> Setup;
    fn legal_moves(&self) -> MoveList;
    fn is_variant_end(&self) -> bool;
    fn has_insufficient_material(&self, color: Color) -> bool;
    fn variant_outcome(&self) -> Option<Outcome>;
    fn play_unchecked(&mut self, m: &Move);

    // Provided methods
    fn san_candidates(&self, role: Role, to: Square) -> MoveList { ... }
    fn castling_moves(&self, side: CastlingSide) -> MoveList { ... }
    fn en_passant_moves(&self) -> MoveList { ... }
    fn capture_moves(&self) -> MoveList { ... }
    fn promotion_moves(&self) -> MoveList { ... }
    fn is_irreversible(&self, m: &Move) -> bool { ... }
    fn king_attackers(
        &self,
        square: Square,
        attacker: Color,
        occupied: Bitboard
    ) -> Bitboard { ... }
    fn us(&self) -> Bitboard { ... }
    fn our(&self, role: Role) -> Bitboard { ... }
    fn them(&self) -> Bitboard { ... }
    fn their(&self, role: Role) -> Bitboard { ... }
    fn is_legal(&self, m: &Move) -> bool { ... }
    fn pseudo_legal_ep_square(&self) -> Option<Square> { ... }
    fn legal_ep_square(&self) -> Option<Square> { ... }
    fn ep_square(&self, mode: EnPassantMode) -> Option<Square> { ... }
    fn checkers(&self) -> Bitboard { ... }
    fn is_check(&self) -> bool { ... }
    fn is_checkmate(&self) -> bool { ... }
    fn is_stalemate(&self) -> bool { ... }
    fn is_insufficient_material(&self) -> bool { ... }
    fn is_game_over(&self) -> bool { ... }
    fn outcome(&self) -> Option<Outcome> { ... }
    fn play(self, m: &Move) -> Result<Self, PlayError<Self>>
       where Self: Sized { ... }
    fn swap_turn(self) -> Result<Self, PositionError<Self>>
       where Self: Sized + FromSetup { ... }
}

Expand description

A playable chess or chess variant position. See Chess for a concrete implementation.

§Equality

All provided variants implement Hash, PartialEq, and Eq according to FIDE rules for repeated positions. That is, considering

piece positions
promoted pieces only in Crazyhouse
pockets only in Crazyhouse
turn
current castling rights
currently available legal en passant moves
remaining checks only in Three-Check

but specifally ignoring halfmove and fullmove counters.

Use Setup for structural equality.

Required Methods§

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fn board(&self) -> &Board

Piece positions on the board.

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fn promoted(&self) -> Bitboard

Positions of tracked promoted pieces. Used only for Crazyhouse.

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fn pockets(&self) -> Option<&ByColor<ByRole<u8>>>

Pockets in Crazyhouse.

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fn turn(&self) -> Color

Side to move.

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fn castles(&self) -> &Castles

Castling paths and unmoved rooks.

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fn maybe_ep_square(&self) -> Option<Square>

Unconditionally gets the en passant target square after a double pawn push, even if no en passant capture is actually possible.

Also see Position::pseudo_legal_ep_square() and Position::legal_ep_square().

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fn remaining_checks(&self) -> Option<&ByColor<RemainingChecks>>

Remaining checks in Three-Check.

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fn halfmoves(&self) -> u32

Number of half-moves since the last capture or pawn move.

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fn fullmoves(&self) -> NonZeroU32

Move number. Starts at 1 and is increased after every black move.

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fn into_setup(self, mode: EnPassantMode) -> Setup

Converts the position to the current Setup.

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fn legal_moves(&self) -> MoveList

Generates all legal moves.

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fn is_variant_end(&self) -> bool

Checks if the game is over due to a special variant end condition.

Note that for example stalemate is not considered a variant-specific end condition (is_variant_end() will return false), but it can have a special variant_outcome() in suicide chess.

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fn has_insufficient_material(&self, color: Color) -> bool

Tests if a side has insufficient winning material.

Returns false if there is any series of legal moves that allows color to win the game.

The converse is not necessarily true for this static check. The position might be locked up such that color can never win the game (even if !color cooperates), or insufficient material might only become apparent after a forced sequence of moves.

The minimum guarantee is: Looking only at the material configuration, taking into account color complexes of bishops and knights, but not concrete piece positions, is there a position with the same material configuration where color can win with a series of legal moves? If not, then color has insufficient winning material.

For a complete dynamic unwinnability solver see https://chasolver.org/.

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fn variant_outcome(&self) -> Option<Outcome>

Tests special variant winning, losing and drawing conditions.

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fn play_unchecked(&mut self, m: &Move)

Plays a move. It is the callers responsibility to ensure the move is legal.

§Panics

Illegal moves can corrupt the state of the position and may (or may not) panic or cause panics on future calls. Consider using Position::play() if you cannot guarantee legality.

Provided Methods§

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fn san_candidates(&self, role: Role, to: Square) -> MoveList

Generates a subset of legal moves: All piece moves and drops of type role to the square to, excluding castling moves.

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fn castling_moves(&self, side: CastlingSide) -> MoveList

Generates legal castling moves.

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fn en_passant_moves(&self) -> MoveList

Generates en passant moves.

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fn capture_moves(&self) -> MoveList

Generates capture moves.

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fn promotion_moves(&self) -> MoveList

Generate promotion moves.

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fn is_irreversible(&self, m: &Move) -> bool

Tests if a move is irreversible.

In standard chess, pawn moves, captures, moves that destroy castling rights, and moves that cede en-passant are irreversible.

The implementation has false-negatives, because it does not consider forced lines. For example, a checking move that will force the king to lose castling rights is not considered irreversible, only the actual king move is.

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