#include <libchess/game/Position.hpp>

Collaboration diagram for ben_bot::Position:

Public Types
using	Hash = std::uint64_t

Public Member Functions
	Position ()
void	flip ()
auto	free () const noexcept -> Bitboard
template<Color Side>
auto	get_backward_pawns () const noexcept -> Bitboard
template<Color Side>
auto	get_passed_pawns () const noexcept -> Bitboard
auto	is_black_to_move () const noexcept -> bool
auto	is_capture (Move move) const noexcept -> bool
auto	is_check () const noexcept -> bool
auto	is_en_passant (Move move) const noexcept -> bool
auto	is_illegal () const -> std::optional< std::string >
auto	is_legal (Move move) const -> bool
auto	is_quiet (Move move) const noexcept -> bool
auto	is_white_to_move () const noexcept -> bool
void	make_move (Move move)
void	make_null_move ()
auto	occupied () const noexcept -> Bitboard
auto	operator== (const Position &other) const noexcept -> bool
void	refresh_zobrist ()
Piece access
template<Color Side>
auto	pieces_for () noexcept -> Pieces &
template<Color Side>
auto	pieces_for () const noexcept -> const Pieces &
template<Color Side>
auto	castling_rights_for () const noexcept -> CastlingRights
auto	our_pieces () noexcept -> Pieces &
auto	our_pieces () const noexcept -> const Pieces &
auto	their_pieces () noexcept -> Pieces &
auto	their_pieces () const noexcept -> const Pieces &
File queries
auto	is_file_open (File file) const noexcept -> bool
auto	get_open_files () const noexcept
auto	is_file_half_open (File file) const noexcept -> bool
auto	get_half_open_files () const noexcept
Game result queries
auto	is_checkmate () const -> bool
auto	is_stalemate () const -> bool
auto	is_fifty_move_draw () const -> bool
auto	is_threefold_repetition () const noexcept -> bool
auto	is_draw_by_insufficient_material () const noexcept -> bool
auto	is_draw () const -> bool
auto	get_result () const -> std::optional< Result >

Static Public Member Functions
static auto	empty () -> Position

Public Attributes
CastlingRights	blackCastlingRights
Pieces	blackPieces { Color::Black }
std::optional< Square >	enPassantTargetSquare
std::uint_least64_t	fullMoveCounter { UINT64_C(1) }
std::uint_least8_t	halfmoveClock { UINT8_C(0) }
Hash	hash { UINT64_C(0) }
Color	sideToMove { Color::White }
CastlingRights	whiteCastlingRights
Pieces	whitePieces { Color::White }

Related Symbols
(Note that these are not member symbols.)
auto	after_move (const Position &starting, Move move) -> Position
auto	after_null_move (const Position &starting) -> Position
auto	flipped (const Position &starting) -> Position
auto	print_ascii (const Position &position) -> std::string
auto	print_utf8 (const Position &position) -> std::string

Detailed Description

This class models an instant in a game of chess.

It describes where all the pieces are placed, as well as some additional metadata such as castling rights, side to move, en passant possibility, etc.

Definition at line 74 of file Position.hpp.

Member Typedef Documentation

◆ Hash

using chess::game::Position::Hash = std::uint64_t

Unsigned 64-bit integer used for hash values.

Definition at line 130 of file Position.hpp.

Constructor & Destructor Documentation

◆ Position()

chess::game::Position::Position ( )

Creates a Position object representing the starting position.

Member Function Documentation

◆ castling_rights_for()

template<Color Side>

auto chess::game::Position::castling_rights_for ( ) const -> CastlingRights

inlinenodiscardnoexcept

Returns the castling rights for the given color.

Definition at line 170 of file Position.hpp.

◆ empty()

auto chess::game::Position::empty ( ) -> Position

inlinestaticnodiscard

Returns an empty position with none of the piece bitboards initialized. This is useful for tasks like parsing a FEN string, for example. After you've set up the position, don't forget to call whitePieces.refresh_occupied(), blackPieces.refresh_occupied(), and refresh_zobrist() to update all relevant cached state.

Definition at line 427 of file Position.hpp.

◆ flip()

void chess::game::Position::flip ( )

Performs a color flip of this position.

◆ free()

auto chess::game::Position::free ( ) const -> Bitboard

inlinenodiscardnoexcept

Returns a bitboard that is the inverse of the occupied() board.

Definition at line 234 of file Position.hpp.

◆ get_backward_pawns()

template<Color Side>

auto chess::game::Position::get_backward_pawns ( ) const -> Bitboard

nodiscardnoexcept

Returns a bitboard containing the locations of backward pawns for the given side.

Definition at line 522 of file Position.hpp.

◆ get_half_open_files()

auto chess::game::Position::get_half_open_files ( ) const

inlinenodiscardnoexcept

Returns an iterable range of File enumeration values corresponding to all half-open files in this position.

See also: is_file_half_open()

Definition at line 501 of file Position.hpp.

◆ get_open_files()

auto chess::game::Position::get_open_files ( ) const

inlinenodiscardnoexcept

Returns an iterable range of File enumeration values corresponding to all open files in this position.

See also: is_file_open()

Definition at line 486 of file Position.hpp.

◆ get_passed_pawns()

template<Color Side>

auto chess::game::Position::get_passed_pawns ( ) const -> Bitboard

nodiscardnoexcept

Returns a bitboard containing the locations of passed pawns for the given side.

Definition at line 508 of file Position.hpp.

◆ get_result()

auto chess::game::Position::get_result ( ) const -> std::optional< Result >

nodiscard

If this position is a conclusive draw or checkmate, returns the appropriate Result enumeration. Returns nullopt if this position is not a conclusive one.

◆ is_black_to_move()

auto chess::game::Position::is_black_to_move ( ) const -> bool

inlinenodiscardnoexcept

Returns true if the side to move is Black.

Definition at line 223 of file Position.hpp.

◆ is_capture()

auto chess::game::Position::is_capture ( Move move ) const -> bool

inlinenodiscardnoexcept

Returns true if the given move is a capture, including en passant.

Definition at line 471 of file Position.hpp.

◆ is_check()

auto chess::game::Position::is_check ( ) const -> bool

inlinenodiscardnoexcept

Returns true if the king of the side to move is in check.

Definition at line 266 of file Position.hpp.

◆ is_checkmate()

auto chess::game::Position::is_checkmate ( ) const -> bool

nodiscard

Returns true if the king is attacked and the side to move has no legal moves.

◆ is_draw()

auto chess::game::Position::is_draw ( ) const -> bool

nodiscard

Returns true if the game has concluded in a draw.

◆ is_draw_by_insufficient_material()

auto chess::game::Position::is_draw_by_insufficient_material ( ) const -> bool

nodiscardnoexcept

Returns true if this position is either lone kings or lone king vs. king and bishop or knight.

◆ is_en_passant()

auto chess::game::Position::is_en_passant ( Move move ) const -> bool

inlinenodiscardnoexcept

Returns true if the given move is an en passant capture in the current position.

Definition at line 464 of file Position.hpp.

◆ is_fifty_move_draw()

auto chess::game::Position::is_fifty_move_draw ( ) const -> bool

nodiscard

Returns true if this position is a fifty-move draw, based on the halfmoveClock. Note that in order for the game to be drawn, the side to move must have at least 1 legal move.

◆ is_file_half_open()

auto chess::game::Position::is_file_half_open ( File file ) const -> bool

inlinenodiscardnoexcept

Returns true if only one side has a pawn on the given file.

See also: get_half_open_files

Definition at line 492 of file Position.hpp.

◆ is_file_open()

auto chess::game::Position::is_file_open ( File file ) const -> bool

inlinenodiscardnoexcept

Returns true if there are no pawns of either color on the given file.

See also: get_open_files()

Definition at line 481 of file Position.hpp.

◆ is_illegal()

auto chess::game::Position::is_illegal ( ) const -> std::optional< std::string >

nodiscard

Tests if the position is legal. If it is, returns nullopt; if the position is illegal, returns an explanatory string describing the error condition detecting. This function conducts basic checks about the number of each type of piece, but this is not an exhaustive validation that a position can definitively be reached from the starting position.

◆ is_legal()

auto chess::game::Position::is_legal ( Move move ) const -> bool

inlinenodiscard

Returns true if the given move is legal (that is, the king is not left in check). This function does not verify piece movement mechanics or that a piece of the given type exists on the starting square; this function only verifies that making the move does not leave the side's king in check.

Definition at line 455 of file Position.hpp.

◆ is_quiet()

auto chess::game::Position::is_quiet ( Move move ) const -> bool

inlinenodiscardnoexcept

Returns true if the given move is quiet - ie, does not alter material.

Definition at line 476 of file Position.hpp.

◆ is_stalemate()

auto chess::game::Position::is_stalemate ( ) const -> bool

nodiscard

Returns true if the side to move has no legal moves, but their king is not attacked.

◆ is_threefold_repetition()

auto chess::game::Position::is_threefold_repetition ( ) const -> bool

inlinenodiscardnoexcept

Returns true if this position is a draw by threefold repetition.

Definition at line 439 of file Position.hpp.

◆ is_white_to_move()

auto chess::game::Position::is_white_to_move ( ) const -> bool

inlinenodiscardnoexcept

Returns true if the side to move is White.

Definition at line 217 of file Position.hpp.

◆ make_move()

void chess::game::Position::make_move ( Move move )

Makes a move to alter the position.

◆ make_null_move()

void chess::game::Position::make_null_move ( )

Makes a null move. This essentially represents the side to move "passing" their turn. This does update the Zobrist hash, halfmove clock and fullmove counter in the same way that make_move() does.

◆ occupied()

auto chess::game::Position::occupied ( ) const -> Bitboard

inlinenodiscardnoexcept

Returns a bitboard that is the union of all White and Black piece positions.

Definition at line 231 of file Position.hpp.

◆ operator==()

auto chess::game::Position::operator== ( const Position & other ) const -> bool

inlinenodiscardnoexcept

Returns true if the two positions have the same Zobrist hash.

Definition at line 140 of file Position.hpp.

◆ our_pieces() [1/2]

auto chess::game::Position::our_pieces ( ) const -> const Pieces &

inlinenodiscardnoexcept

Returns the pieces belonging to the side to move.

Definition at line 188 of file Position.hpp.

◆ our_pieces() [2/2]

auto chess::game::Position::our_pieces ( ) -> Pieces &

inlinenodiscardnoexcept

Returns the pieces belonging to the side to move.

Definition at line 179 of file Position.hpp.

◆ pieces_for() [1/2]

template<Color Side>

auto chess::game::Position::pieces_for ( ) const -> const Pieces &

inlinenodiscardnoexcept

Returns the piece set representing the given color.

Definition at line 160 of file Position.hpp.

◆ pieces_for() [2/2]

template<Color Side>

auto chess::game::Position::pieces_for ( ) -> Pieces &

inlinenodiscardnoexcept

Returns the piece set representing the given color.

Definition at line 150 of file Position.hpp.

◆ refresh_zobrist()

void chess::game::Position::refresh_zobrist ( )

Recalculates the Zobrist hash for this position.

◆ their_pieces() [1/2]

auto chess::game::Position::their_pieces ( ) const -> const Pieces &

inlinenodiscardnoexcept

Returns the pieces belonging to the side-to-move's opponent.

Definition at line 206 of file Position.hpp.

◆ their_pieces() [2/2]

auto chess::game::Position::their_pieces ( ) -> Pieces &

inlinenodiscardnoexcept

Returns the pieces belonging to the side-to-move's opponent.

Definition at line 197 of file Position.hpp.

Member Data Documentation

◆ blackCastlingRights

CastlingRights chess::game::Position::blackCastlingRights

Castling rights for the Black player.

Definition at line 101 of file Position.hpp.

◆ blackPieces

Pieces chess::game::Position::blackPieces { Color::Black }

The positions of the Black pieces.

Invariant: The bitboard indices of the bits set in blackPieces must not overlap with any of the indices of the bits set in whitePieces.

Definition at line 92 of file Position.hpp.

◆ enPassantTargetSquare

std::optional<Square> chess::game::Position::enPassantTargetSquare

If the last move was a pawn double-push, then this holds the square that a pawn would land on after capturing en passant. This is always set to a non-null value if the last move was a pawn double-push, even if no enemy pawns are actually in position to perform the capture.

Definition at line 109 of file Position.hpp.

◆ fullMoveCounter

std::uint_least64_t chess::game::Position::fullMoveCounter { UINT64_C(1) }

The number of full moves in the game. This value is monotonically increasing throughout the game, and is incremented after every Black move.

Definition at line 127 of file Position.hpp.

◆ halfmoveClock

std::uint_least8_t chess::game::Position::halfmoveClock { UINT8_C(0) }

This is a ply counter that enforces the 50-move rule. The counter is incremented after every move and reset by captures and pawn moves; if the counter reaches 100 and the side to move has at least 1 legal move, then the game is drawn.

Invariant: This value will never be greater than 100.

See also: is_fifty_move_draw()

Definition at line 121 of file Position.hpp.

◆ hash

Hash chess::game::Position::hash { UINT64_C(0) }

The Zobrist hash value of this position. This value is incrementally updated by the make_move() function. If you manually change attributes of the position, call the refresh_zobrist() function to recalculate it.

Definition at line 137 of file Position.hpp.

◆ sideToMove

Color chess::game::Position::sideToMove { Color::White }

Indicates whose move it is in this position.

Definition at line 95 of file Position.hpp.

◆ whiteCastlingRights

CastlingRights chess::game::Position::whiteCastlingRights

Castling rights for the White player.

Definition at line 98 of file Position.hpp.

◆ whitePieces

Pieces chess::game::Position::whitePieces { Color::White }

The positions of the White pieces.

Invariant: The bitboard indices of the bits set in whitePieces must not overlap with any of the indices of the bits set in blackPieces.

Definition at line 84 of file Position.hpp.

The documentation for this struct was generated from the following file:

libchess/include/libchess/game/Position.hpp

Public Types

Public Member Functions

Static Public Member Functions

Public Attributes

Related Symbols

Detailed Description

Member Typedef Documentation

◆ Hash

Constructor & Destructor Documentation

◆ Position()

Member Function Documentation

◆ castling_rights_for()

◆ empty()

◆ flip()

◆ free()

◆ get_backward_pawns()

◆ get_half_open_files()

◆ get_open_files()

◆ get_passed_pawns()

◆ get_result()

◆ is_black_to_move()

◆ is_capture()

◆ is_check()

◆ is_checkmate()

◆ is_draw()

◆ is_draw_by_insufficient_material()

◆ is_en_passant()

◆ is_fifty_move_draw()

◆ is_file_half_open()

◆ is_file_open()

◆ is_illegal()

◆ is_legal()

◆ is_quiet()

◆ is_stalemate()

◆ is_threefold_repetition()

◆ is_white_to_move()

◆ make_move()

◆ make_null_move()

◆ occupied()

◆ operator==()

◆ our_pieces() [1/2]

◆ our_pieces() [2/2]

◆ pieces_for() [1/2]

◆ pieces_for() [2/2]

◆ refresh_zobrist()

◆ their_pieces() [1/2]

◆ their_pieces() [2/2]

Member Data Documentation

◆ blackCastlingRights

◆ blackPieces

◆ enPassantTargetSquare

◆ fullMoveCounter

◆ halfmoveClock

◆ hash

◆ sideToMove

◆ whiteCastlingRights

◆ whitePieces