Struct Position 

pub struct Position { /* private fields */ }

A shogi position with fast do/undo and an incrementally maintained Zobrist key.

The board state is stored redundantly (mailbox + bitboards); moves are assumed to be legal (generate them with Position::legal_moves). A side may have no king (as in tsume-shogi problems).

A Position is a plain value: it owns nothing on the heap, so cloning it copies and does not allocate.

Implementations

impl Position

pub fn generate_moves( &self, listener: impl FnMut(MoveSet) -> ControlFlow<()>, ) -> ControlFlow<()>

Calls listener with every group of legal moves for the side to move, including pawn-drop-mate exclusion.

Returning ControlFlow::Break from listener stops generation early — useful to answer “is there any legal move?” without building the rest — and is reported back as the return value, so the caller can tell a full walk from an interrupted one. No empty MoveSet is ever passed.

The opponent’s king square is never a destination: in illegal positions where that king could already be captured (unreachable through legal play, but constructible via Position::new), no king-capture move is generated — the rest of the result is unspecified there, but this function does not panic.

pub fn legal_moves(&self) -> Vec<Move>

All legal moves for the side to move.

The compatibility wrapper over Position::generate_moves; prefer the callback form in hot code, which allocates nothing.

pub fn has_legal_moves(&self) -> bool

Whether the side to move has at least one legal move.

Stops at the first group found, so it is far cheaper than !legal_moves().is_empty().

pub fn in_check(&self) -> bool

Whether the side to move is in check.

impl Position

pub fn new(partial: PartialPosition) -> Self

Builds a Position from a PartialPosition.

pub fn startpos() -> Self

The initial position.

pub fn piece_at(&self, square: Square) -> Option<Piece>

The piece on square, if any.

pub fn side_to_move(&self) -> Color

The player to move.

pub fn ply(&self) -> u16

The current ply (1 at the start of a game).

pub fn hand(&self, color: Color) -> Hand

The hand of color.

pub fn king_square(&self, color: Color) -> Option<Square>

The square of color’s king, if it is on the board.

pub fn key(&self) -> u64

The Zobrist key (board, hands and side to move).

pub fn occupied(&self) -> Bitboard

The squares occupied by pieces of either color.

pub fn player_bb(&self, color: Color) -> Bitboard

The squares occupied by color’s pieces.

pub fn piece_kind_bb(&self, piece_kind: PieceKind) -> Bitboard

The squares occupied by pieces of piece_kind, either color.

pub fn do_move(&mut self, mv: Move) -> Undo

Makes mv on the board. mv must be legal in this position.

Returns what Position::undo_move needs to take it back. Moves are undone in the reverse of the order they were made, each with its own Undo.

pub fn undo_move(&mut self, mv: Move, undo: Undo)

Undoes mv, the last move made with Position::do_move, using the Undo that call returned.

Trait Implementations

impl Clone for Position

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Position

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Draws the board as seen by Black, with USI piece letters.

impl Default for Position

fn default() -> Self

Returns the “default value” for a type.

impl Eq for Position

impl From<PartialPosition> for Position

fn from(partial: PartialPosition) -> Self

Converts to this type from the input type.

impl PartialEq for Position

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for Position