Class: PGN::Position

Inherits:
Object
  • Object
show all
Defined in:
lib/pgn/position.rb

Overview

Position encapsulates all of the information necessary to completely understand a chess position. It can be turned into a FEN string or perform a move.

Constant Summary collapse

PLAYERS = 
[:white, :black]
CASTLING = 
%w{K Q k q}

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(board, player, castling = CASTLING, en_passant = nil, halfmove = 0, fullmove = 1) ⇒ Position

Returns a new instance of Position.

Examples:

PGN::Position.new(
  PGN::Board.start,
  :white,
)

Parameters:

  • board (PGN::Board) —

    the board for the position

  • player (Symbol) —

    the player who moves next

  • castling (Array<String>) (defaults to: CASTLING) —

    the castling moves that are still available

  • en_passant (String, nil) (defaults to: nil) —

    the en passant square if applicable

  • halfmove (Integer) (defaults to: 0) —

    the number of halfmoves since the last pawn move or capture

  • fullmove (Integer) (defaults to: 1) —

    the number of fullmoves made so far



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# File 'lib/pgn/position.rb', line 64

def initialize(board, player, castling = CASTLING, en_passant = nil, halfmove = 0, fullmove = 1)
  self.board      = board
  self.player     = player
  self.castling   = castling
  self.en_passant = en_passant
  self.halfmove   = halfmove
  self.fullmove   = fullmove
end

Instance Attribute Details

#board ⇒ PGN::Board

Returns the board for the position.

Returns:



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# File 'lib/pgn/position.rb', line 29

class Position
  PLAYERS  = [:white, :black]
  CASTLING = %w{K Q k q}

  attr_accessor :board
  attr_accessor :player
  attr_accessor :castling
  attr_accessor :en_passant
  attr_accessor :halfmove
  attr_accessor :fullmove

  # @return [PGN::Position] the starting position of a chess game
  #
  def self.start
    PGN::Position.new(
      PGN::Board.start,
      PLAYERS.first,
    )
  end

  # @param board [PGN::Board] the board for the position
  # @param player [Symbol] the player who moves next
  # @param castling [Array<String>] the castling moves that are still
  #   available
  # @param en_passant [String, nil] the en passant square if applicable
  # @param halfmove [Integer] the number of halfmoves since the last pawn
  #   move or capture
  # @param fullmove [Integer] the number of fullmoves made so far
  #
  # @example
  #   PGN::Position.new(
  #     PGN::Board.start,
  #     :white,
  #   )
  #
  def initialize(board, player, castling = CASTLING, en_passant = nil, halfmove = 0, fullmove = 1)
    self.board      = board
    self.player     = player
    self.castling   = castling
    self.en_passant = en_passant
    self.halfmove   = halfmove
    self.fullmove   = fullmove
  end 

  # @param str [String] the move to make in SAN
  # @return [PGN::Position] the resulting position
  #
  # @example
  #   queens_pawn = PGN::Position.start.move("d4")
  #
  def move(str)
    move       = PGN::Move.new(str, self.player)
    calculator = PGN::MoveCalculator.new(self.board, move)

    new_castling = self.castling - calculator.castling_restrictions
    new_halfmove = calculator.increment_halfmove? ?
      self.halfmove + 1 :
      0
    new_fullmove = calculator.increment_fullmove? ?
      self.fullmove + 1 :
      self.fullmove

    PGN::Position.new(
      calculator.result_board,
      self.next_player,
      new_castling,
      calculator.en_passant_square,
      new_halfmove,
      new_fullmove,
    )
  end

  # @return [Symbol] the next player to move
  #
  def next_player
    (PLAYERS - [self.player]).first
  end

  def inspect
    "\n" + self.board.inspect
  end

  # @return [PGN::FEN] a {PGN::FEN} object representing the current position
  #
  def to_fen
    PGN::FEN.from_attributes(
      board:      self.board,
      active:     self.player == :white ? 'w' : 'b',
      castling:   self.castling.join(''),
      en_passant: self.en_passant,
      halfmove:   self.halfmove.to_s,
      fullmove:   self.fullmove.to_s,
    )
  end

end

#castling ⇒ Array<String>

Returns the castling moves that are still available.

Examples:

position.castling #=> ["K", "k", "q"]

Returns:

  • (Array<String>) —

    the castling moves that are still available



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# File 'lib/pgn/position.rb', line 29

class Position
  PLAYERS  = [:white, :black]
  CASTLING = %w{K Q k q}

  attr_accessor :board
  attr_accessor :player
  attr_accessor :castling
  attr_accessor :en_passant
  attr_accessor :halfmove
  attr_accessor :fullmove

  # @return [PGN::Position] the starting position of a chess game
  #
  def self.start
    PGN::Position.new(
      PGN::Board.start,
      PLAYERS.first,
    )
  end

  # @param board [PGN::Board] the board for the position
  # @param player [Symbol] the player who moves next
  # @param castling [Array<String>] the castling moves that are still
  #   available
  # @param en_passant [String, nil] the en passant square if applicable
  # @param halfmove [Integer] the number of halfmoves since the last pawn
  #   move or capture
  # @param fullmove [Integer] the number of fullmoves made so far
  #
  # @example
  #   PGN::Position.new(
  #     PGN::Board.start,
  #     :white,
  #   )
  #
  def initialize(board, player, castling = CASTLING, en_passant = nil, halfmove = 0, fullmove = 1)
    self.board      = board
    self.player     = player
    self.castling   = castling
    self.en_passant = en_passant
    self.halfmove   = halfmove
    self.fullmove   = fullmove
  end 

  # @param str [String] the move to make in SAN
  # @return [PGN::Position] the resulting position
  #
  # @example
  #   queens_pawn = PGN::Position.start.move("d4")
  #
  def move(str)
    move       = PGN::Move.new(str, self.player)
    calculator = PGN::MoveCalculator.new(self.board, move)

    new_castling = self.castling - calculator.castling_restrictions
    new_halfmove = calculator.increment_halfmove? ?
      self.halfmove + 1 :
      0
    new_fullmove = calculator.increment_fullmove? ?
      self.fullmove + 1 :
      self.fullmove

    PGN::Position.new(
      calculator.result_board,
      self.next_player,
      new_castling,
      calculator.en_passant_square,
      new_halfmove,
      new_fullmove,
    )
  end

  # @return [Symbol] the next player to move
  #
  def next_player
    (PLAYERS - [self.player]).first
  end

  def inspect
    "\n" + self.board.inspect
  end

  # @return [PGN::FEN] a {PGN::FEN} object representing the current position
  #
  def to_fen
    PGN::FEN.from_attributes(
      board:      self.board,
      active:     self.player == :white ? 'w' : 'b',
      castling:   self.castling.join(''),
      en_passant: self.en_passant,
      halfmove:   self.halfmove.to_s,
      fullmove:   self.fullmove.to_s,
    )
  end

end

#en_passant ⇒ String

Returns the en passant square if applicable.

Returns:

  • (String) —

    the en passant square if applicable



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# File 'lib/pgn/position.rb', line 29

class Position
  PLAYERS  = [:white, :black]
  CASTLING = %w{K Q k q}

  attr_accessor :board
  attr_accessor :player
  attr_accessor :castling
  attr_accessor :en_passant
  attr_accessor :halfmove
  attr_accessor :fullmove

  # @return [PGN::Position] the starting position of a chess game
  #
  def self.start
    PGN::Position.new(
      PGN::Board.start,
      PLAYERS.first,
    )
  end

  # @param board [PGN::Board] the board for the position
  # @param player [Symbol] the player who moves next
  # @param castling [Array<String>] the castling moves that are still
  #   available
  # @param en_passant [String, nil] the en passant square if applicable
  # @param halfmove [Integer] the number of halfmoves since the last pawn
  #   move or capture
  # @param fullmove [Integer] the number of fullmoves made so far
  #
  # @example
  #   PGN::Position.new(
  #     PGN::Board.start,
  #     :white,
  #   )
  #
  def initialize(board, player, castling = CASTLING, en_passant = nil, halfmove = 0, fullmove = 1)
    self.board      = board
    self.player     = player
    self.castling   = castling
    self.en_passant = en_passant
    self.halfmove   = halfmove
    self.fullmove   = fullmove
  end 

  # @param str [String] the move to make in SAN
  # @return [PGN::Position] the resulting position
  #
  # @example
  #   queens_pawn = PGN::Position.start.move("d4")
  #
  def move(str)
    move       = PGN::Move.new(str, self.player)
    calculator = PGN::MoveCalculator.new(self.board, move)

    new_castling = self.castling - calculator.castling_restrictions
    new_halfmove = calculator.increment_halfmove? ?
      self.halfmove + 1 :
      0
    new_fullmove = calculator.increment_fullmove? ?
      self.fullmove + 1 :
      self.fullmove

    PGN::Position.new(
      calculator.result_board,
      self.next_player,
      new_castling,
      calculator.en_passant_square,
      new_halfmove,
      new_fullmove,
    )
  end

  # @return [Symbol] the next player to move
  #
  def next_player
    (PLAYERS - [self.player]).first
  end

  def inspect
    "\n" + self.board.inspect
  end

  # @return [PGN::FEN] a {PGN::FEN} object representing the current position
  #
  def to_fen
    PGN::FEN.from_attributes(
      board:      self.board,
      active:     self.player == :white ? 'w' : 'b',
      castling:   self.castling.join(''),
      en_passant: self.en_passant,
      halfmove:   self.halfmove.to_s,
      fullmove:   self.fullmove.to_s,
    )
  end

end

#fullmove ⇒ Integer

Returns the number of fullmoves made so far.

Returns:

  • (Integer) —

    the number of fullmoves made so far



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# File 'lib/pgn/position.rb', line 29

class Position
  PLAYERS  = [:white, :black]
  CASTLING = %w{K Q k q}

  attr_accessor :board
  attr_accessor :player
  attr_accessor :castling
  attr_accessor :en_passant
  attr_accessor :halfmove
  attr_accessor :fullmove

  # @return [PGN::Position] the starting position of a chess game
  #
  def self.start
    PGN::Position.new(
      PGN::Board.start,
      PLAYERS.first,
    )
  end

  # @param board [PGN::Board] the board for the position
  # @param player [Symbol] the player who moves next
  # @param castling [Array<String>] the castling moves that are still
  #   available
  # @param en_passant [String, nil] the en passant square if applicable
  # @param halfmove [Integer] the number of halfmoves since the last pawn
  #   move or capture
  # @param fullmove [Integer] the number of fullmoves made so far
  #
  # @example
  #   PGN::Position.new(
  #     PGN::Board.start,
  #     :white,
  #   )
  #
  def initialize(board, player, castling = CASTLING, en_passant = nil, halfmove = 0, fullmove = 1)
    self.board      = board
    self.player     = player
    self.castling   = castling
    self.en_passant = en_passant
    self.halfmove   = halfmove
    self.fullmove   = fullmove
  end 

  # @param str [String] the move to make in SAN
  # @return [PGN::Position] the resulting position
  #
  # @example
  #   queens_pawn = PGN::Position.start.move("d4")
  #
  def move(str)
    move       = PGN::Move.new(str, self.player)
    calculator = PGN::MoveCalculator.new(self.board, move)

    new_castling = self.castling - calculator.castling_restrictions
    new_halfmove = calculator.increment_halfmove? ?
      self.halfmove + 1 :
      0
    new_fullmove = calculator.increment_fullmove? ?
      self.fullmove + 1 :
      self.fullmove

    PGN::Position.new(
      calculator.result_board,
      self.next_player,
      new_castling,
      calculator.en_passant_square,
      new_halfmove,
      new_fullmove,
    )
  end

  # @return [Symbol] the next player to move
  #
  def next_player
    (PLAYERS - [self.player]).first
  end

  def inspect
    "\n" + self.board.inspect
  end

  # @return [PGN::FEN] a {PGN::FEN} object representing the current position
  #
  def to_fen
    PGN::FEN.from_attributes(
      board:      self.board,
      active:     self.player == :white ? 'w' : 'b',
      castling:   self.castling.join(''),
      en_passant: self.en_passant,
      halfmove:   self.halfmove.to_s,
      fullmove:   self.fullmove.to_s,
    )
  end

end

#halfmove ⇒ Integer

Returns the number of halfmoves since the last pawn move or capture.

Returns:

  • (Integer) —

    the number of halfmoves since the last pawn move or capture



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# File 'lib/pgn/position.rb', line 29

class Position
  PLAYERS  = [:white, :black]
  CASTLING = %w{K Q k q}

  attr_accessor :board
  attr_accessor :player
  attr_accessor :castling
  attr_accessor :en_passant
  attr_accessor :halfmove
  attr_accessor :fullmove

  # @return [PGN::Position] the starting position of a chess game
  #
  def self.start
    PGN::Position.new(
      PGN::Board.start,
      PLAYERS.first,
    )
  end

  # @param board [PGN::Board] the board for the position
  # @param player [Symbol] the player who moves next
  # @param castling [Array<String>] the castling moves that are still
  #   available
  # @param en_passant [String, nil] the en passant square if applicable
  # @param halfmove [Integer] the number of halfmoves since the last pawn
  #   move or capture
  # @param fullmove [Integer] the number of fullmoves made so far
  #
  # @example
  #   PGN::Position.new(
  #     PGN::Board.start,
  #     :white,
  #   )
  #
  def initialize(board, player, castling = CASTLING, en_passant = nil, halfmove = 0, fullmove = 1)
    self.board      = board
    self.player     = player
    self.castling   = castling
    self.en_passant = en_passant
    self.halfmove   = halfmove
    self.fullmove   = fullmove
  end 

  # @param str [String] the move to make in SAN
  # @return [PGN::Position] the resulting position
  #
  # @example
  #   queens_pawn = PGN::Position.start.move("d4")
  #
  def move(str)
    move       = PGN::Move.new(str, self.player)
    calculator = PGN::MoveCalculator.new(self.board, move)

    new_castling = self.castling - calculator.castling_restrictions
    new_halfmove = calculator.increment_halfmove? ?
      self.halfmove + 1 :
      0
    new_fullmove = calculator.increment_fullmove? ?
      self.fullmove + 1 :
      self.fullmove

    PGN::Position.new(
      calculator.result_board,
      self.next_player,
      new_castling,
      calculator.en_passant_square,
      new_halfmove,
      new_fullmove,
    )
  end

  # @return [Symbol] the next player to move
  #
  def next_player
    (PLAYERS - [self.player]).first
  end

  def inspect
    "\n" + self.board.inspect
  end

  # @return [PGN::FEN] a {PGN::FEN} object representing the current position
  #
  def to_fen
    PGN::FEN.from_attributes(
      board:      self.board,
      active:     self.player == :white ? 'w' : 'b',
      castling:   self.castling.join(''),
      en_passant: self.en_passant,
      halfmove:   self.halfmove.to_s,
      fullmove:   self.fullmove.to_s,
    )
  end

end

#player ⇒ Symbol

Returns the player who moves next.

Examples:

position.player #=> :white

Returns:

  • (Symbol) —

    the player who moves next



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# File 'lib/pgn/position.rb', line 29

class Position
  PLAYERS  = [:white, :black]
  CASTLING = %w{K Q k q}

  attr_accessor :board
  attr_accessor :player
  attr_accessor :castling
  attr_accessor :en_passant
  attr_accessor :halfmove
  attr_accessor :fullmove

  # @return [PGN::Position] the starting position of a chess game
  #
  def self.start
    PGN::Position.new(
      PGN::Board.start,
      PLAYERS.first,
    )
  end

  # @param board [PGN::Board] the board for the position
  # @param player [Symbol] the player who moves next
  # @param castling [Array<String>] the castling moves that are still
  #   available
  # @param en_passant [String, nil] the en passant square if applicable
  # @param halfmove [Integer] the number of halfmoves since the last pawn
  #   move or capture
  # @param fullmove [Integer] the number of fullmoves made so far
  #
  # @example
  #   PGN::Position.new(
  #     PGN::Board.start,
  #     :white,
  #   )
  #
  def initialize(board, player, castling = CASTLING, en_passant = nil, halfmove = 0, fullmove = 1)
    self.board      = board
    self.player     = player
    self.castling   = castling
    self.en_passant = en_passant
    self.halfmove   = halfmove
    self.fullmove   = fullmove
  end 

  # @param str [String] the move to make in SAN
  # @return [PGN::Position] the resulting position
  #
  # @example
  #   queens_pawn = PGN::Position.start.move("d4")
  #
  def move(str)
    move       = PGN::Move.new(str, self.player)
    calculator = PGN::MoveCalculator.new(self.board, move)

    new_castling = self.castling - calculator.castling_restrictions
    new_halfmove = calculator.increment_halfmove? ?
      self.halfmove + 1 :
      0
    new_fullmove = calculator.increment_fullmove? ?
      self.fullmove + 1 :
      self.fullmove

    PGN::Position.new(
      calculator.result_board,
      self.next_player,
      new_castling,
      calculator.en_passant_square,
      new_halfmove,
      new_fullmove,
    )
  end

  # @return [Symbol] the next player to move
  #
  def next_player
    (PLAYERS - [self.player]).first
  end

  def inspect
    "\n" + self.board.inspect
  end

  # @return [PGN::FEN] a {PGN::FEN} object representing the current position
  #
  def to_fen
    PGN::FEN.from_attributes(
      board:      self.board,
      active:     self.player == :white ? 'w' : 'b',
      castling:   self.castling.join(''),
      en_passant: self.en_passant,
      halfmove:   self.halfmove.to_s,
      fullmove:   self.fullmove.to_s,
    )
  end

end

Class Method Details

.start ⇒ PGN::Position

Returns the starting position of a chess game.

Returns:



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# File 'lib/pgn/position.rb', line 42

def self.start
  PGN::Position.new(
    PGN::Board.start,
    PLAYERS.first,
  )
end

Instance Method Details

#inspect ⇒ Object 



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# File 'lib/pgn/position.rb', line 107

def inspect
  "\n" + self.board.inspect
end

#move(str) ⇒ PGN::Position

Returns the resulting position.

Examples:

queens_pawn = PGN::Position.start.move("d4")

Parameters:

  • str (String) —

    the move to make in SAN

Returns:



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# File 'lib/pgn/position.rb', line 79

def move(str)
  move       = PGN::Move.new(str, self.player)
  calculator = PGN::MoveCalculator.new(self.board, move)

  new_castling = self.castling - calculator.castling_restrictions
  new_halfmove = calculator.increment_halfmove? ?
    self.halfmove + 1 :
    0
  new_fullmove = calculator.increment_fullmove? ?
    self.fullmove + 1 :
    self.fullmove

  PGN::Position.new(
    calculator.result_board,
    self.next_player,
    new_castling,
    calculator.en_passant_square,
    new_halfmove,
    new_fullmove,
  )
end

#next_player ⇒ Symbol

Returns the next player to move.

Returns:

  • (Symbol) —

    the next player to move



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# File 'lib/pgn/position.rb', line 103

def next_player
  (PLAYERS - [self.player]).first
end

#to_fen ⇒ PGN::FEN

Returns a FEN object representing the current position.

Returns:

  • (PGN::FEN) —

    a FEN object representing the current position



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# File 'lib/pgn/position.rb', line 113

def to_fen
  PGN::FEN.from_attributes(
    board:      self.board,
    active:     self.player == :white ? 'w' : 'b',
    castling:   self.castling.join(''),
    en_passant: self.en_passant,
    halfmove:   self.halfmove.to_s,
    fullmove:   self.fullmove.to_s,
  )
end