Sage - 开源的 Swift 国际象棋库

Usage

Game Management

Running a chess game can be as simple as setting up a loop.

import Sage

let game = Game()

while !game.isFinished {
    let move = ...
    try game.execute(move: move)
}

Move Generation

Sage is capable of generating legal moves for the current player with full support for special moves such as en passant and castling.

• availableMoves() will return all moves currently available.

• movesForPiece(at:) will return all moves for a piece at a square.

• movesBitboardForPiece(at:) will return a Bitboard containing all of the squares a piece at a square can move to.

Move Validation

Sage can also validate whether a move is legal with the isLegal(move:) method for a Game state.

The execute(move:) family of methods calls this method, so it would be faster to execute the move directly and catch any error from an illegal move.

Undo and Redo Moves

Move undo and redo operations are done with the undoMove() and redoMove() methods. The undone or redone move is returned.

To just check what moves are to be undone or redone, the moveToUndo() and moveToRedo() methods are available.

Promotion Handling

The execute(move:promotion:) method takes a closure that returns a promotion piece. This allows for the app to prompt the user for a promotion piece or perform any other operations before choosing a promotion piece.

try game.execute(move: move) {
    ...
    return .queen(game.playerTurn)
}

The closure is only executed if the move is a pawn promotion. An error is thrown if the promotion piece is the wrong color or cannot promote a pawn, such as with a king or pawn.

A piece can be given without a closure. The default promotion piece is a queen.

try game.execute(move: move, promotion: .queen(game.playerTurn))

Pretty Printing

The Board and Bitboard types both have an ascii property that can be used to print a visual board.

let board = Board()

print(board.ascii)
//   +-----------------+
// 8 | r n b q k b n r |
// 7 | p p p p p p p p |
// 6 | . . . . . . . . |
// 5 | . . . . . . . . |
// 4 | . . . . . . . . |
// 3 | . . . . . . . . |
// 2 | P P P P P P P P |
// 1 | R N B Q K B N R |
//   +-----------------+
//     a b c d e f g h

print(board.bitboard().ascii)
//   +-----------------+
// 8 | 1 1 1 1 1 1 1 1 |
// 7 | 1 1 1 1 1 1 1 1 |
// 6 | . . . . . . . . |
// 5 | . . . . . . . . |
// 4 | . . . . . . . . |
// 3 | . . . . . . . . |
// 2 | 1 1 1 1 1 1 1 1 |
// 1 | 1 1 1 1 1 1 1 1 |
//   +-----------------+
//     a b c d e f g h

Forsyth–Edwards Notation

The Game.Position and Board types can both generate a FEN string.

let game = Game()

print(game.position.fen())
// rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1

print(game.board.fen())
// rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR

They can also be initialized from a FEN string.

assert(Board(fen: game.board.fen()) == game.board)

assert(Game.Position(fen: game.position.fen()) == game.position)

Iterating Through a Board

The Board type conforms to Sequence, making iterating through its spaces seamless.

for space in Board() {
    if let piece = space.piece {
        print("\(piece) at \(space.square)")
    }
}

Squares to Moves

Sequence and Square have two methods that return an array of moves that go from/to self to/from the parameter.

print([.a1, .h3, .b5].moves(from: .b4))
// [b4 >>> a1, b4 >>> h3, b4 >>> b5]

print([.c3, .d2, .f1].moves(to: .a6))
// [c3 >>> a6, d2 >>> a6, f1 >>> a6]

print(Square.d4.moves(from: [.c2, .f8, .h2]))
// [c2 >>> d4, f8 >>> d4, h2 >>> d4]

print(Square.a4.moves(to: [.c3, .d4, .f6]))
// [a4 >>> c3, a4 >>> d4, a4 >>> f6]

Playground Quick Look

Board conforms to the CustomPlaygroundQuickLookable protocol.

License

Sage is published under version 2.0 of the Apache License.