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Sage is a cross-platform chess library for Swift.

• Features
• Installation
  • Compatibility
  • Swift Package Manager
  • CocoaPods
  • Carthage
• Usage
  • Game Management
  • Move Generation
  • Move Validation
  • Undo and Redo Moves
  • Promotion Handling
  • Pretty Printing
  • Forsyth–Edwards Notation
  • Iterating Through a Board
  • Squares to Moves
  • Playground Quick Look
• License

• Chess game management
• Chess board structuring
• Move generation / validation
• En passant and castling
• Pawn promotions
• FEN for games and boards
• Documentation

• Platforms:
  • macOS 10.9+
  • iOS 8.0+
  • watchOS 2.0+
  • tvOS 9.0+
  • Linux
• Xcode 7.3 and 8.0
• Swift 2.2 and 3.0

The Swift Package Manager is a decentralized dependency manager for Swift.

1. Add the project to your Package.swift.

   import PackageDescription
   
   let package = Package(
       name: "MyAwesomeProject",
       dependencies: [
           .Package(url: "https://github.com/nvzqz/Sage.git",
                    majorVersion: 1)
       ]
   )

2. Import the Sage module.

   import Sage

CocoaPods is a centralized dependency manager for Objective-C and Swift. Go here to learn more.

1. Add the project to your Podfile.

   use_frameworks!
   
   pod 'Sage', '~> 1.0.0'

2. Run pod install and open the .xcworkspace file to launch Xcode.

3. Import the Sage framework.

   import Sage

Carthage is a decentralized dependency manager for Objective-C and Swift.

1. Add the project to your Cartfile.

   github "nvzqz/Sage"
   

2. Run carthage update and follow the additional steps in order to add Sage to your project.

3. Import the Sage framework.

   import Sage

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)
}

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.

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.

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.

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))

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

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)

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)")
    }
}

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]

Board conforms to the CustomPlaygroundQuickLookable protocol.

Sage is published under version 2.0 of the Apache License.