Class: PGN::Board

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

Overview

Board represents the squares of a chess board and the pieces on each square. It is responsible for translating between a human readable format (white queen’s rook on the bottom left) and the obvious internal representation (white queen’s rook is position [0,0]). It takes care of converting square names (e4) to actual locations, and can convert to unicode chess pieces for display purposes.

Constant Summary collapse

START =

The starting, internal representation of a chess board

[
  ["R", "P", nil, nil, nil, nil, "p", "r"],
  ["N", "P", nil, nil, nil, nil, "p", "n"],
  ["B", "P", nil, nil, nil, nil, "p", "b"],
  ["Q", "P", nil, nil, nil, nil, "p", "q"],
  ["K", "P", nil, nil, nil, nil, "p", "k"],
  ["B", "P", nil, nil, nil, nil, "p", "b"],
  ["N", "P", nil, nil, nil, nil, "p", "n"],
  ["R", "P", nil, nil, nil, nil, "p", "r"],
]
FILE_TO_INDEX = 
{
  'a' => 0,
  'b' => 1,
  'c' => 2,
  'd' => 3,
  'e' => 4,
  'f' => 5,
  'g' => 6,
  'h' => 7,
}
INDEX_TO_FILE = 

      
        
RANK_TO_INDEX =
          
        

        
{
  '1' => 0,
  '2' => 1,
  '3' => 2,
  '4' => 3,
  '5' => 4,
  '6' => 5,
  '7' => 6,
  '8' => 7,
}

      
        
INDEX_TO_RANK =
          
        

        

      
        
UNICODE_PIECES =
          

  

    

algebraic to unicode piece lookup



  





  



        

        
{
  'k' => "\u{265A}",
  'q' => "\u{265B}",
  'r' => "\u{265C}",
  'b' => "\u{265D}",
  'n' => "\u{265E}",
  'p' => "\u{265F}",
  'K' => "\u{2654}",
  'Q' => "\u{2655}",
  'R' => "\u{2656}",
  'B' => "\u{2657}",
  'N' => "\u{2658}",
  'P' => "\u{2659}",
  nil => '_',
}

      
    

  




  
Instance Attribute Summary collapse

  




  
    

      Class Method Summary
      collapse
    


    
  
    

      Instance Method Summary
      collapse
    


    
  



  
Constructor Details

  
    

  

  
    #initialize(squares)  ⇒ Board 
  

  

  




  

    

Returns a new instance of Board.



  





  
  

    
Examples:

    
      
      
PGN::Board.new(
  [
    ["R", "P", nil, nil, nil, nil, "p", "r"],
    ["N", "P", nil, nil, nil, nil, "p", "n"],
    ["B", "P", nil, nil, nil, nil, "p", "b"],
    ["Q", "P", nil, nil, nil, nil, "p", "q"],
    ["K", "P", nil, nil, nil, nil, "p", "k"],
    ["B", "P", nil, nil, nil, nil, "p", "b"],
    ["N", "P", nil, nil, nil, nil, "p", "n"],
    ["R", "P", nil, nil, nil, nil, "p", "r"],
  ]
)

    
  


Parameters:


    
  
    
  • 
      
        squares
      
      
        (<Array<Array<String>>>)
      
      
      
        —
        
    

    the squares of the board
    

    
      
    
    • 
  






  

    
      


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# File 'lib/pgn/board.rb', line 91

def initialize(squares)
  self.squares = squares
end

    		
  





  



  

    
Instance Attribute Details

    
      
      
      

  

  
    #squares  ⇒ Array<Array<String>> 
  

  

  




  

    

Returns the pieces on the board.



  





  

Returns:


    
  
    
  • 
      
      
        (Array<Array<String>>)
      
      
      
        —
        
    

    the pieces on the board
    

    
      
    
    • 
  





  

    
      


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# File 'lib/pgn/board.rb', line 12

class Board
  # The starting, internal representation of a chess board
  #
  START = [
    ["R", "P", nil, nil, nil, nil, "p", "r"],
    ["N", "P", nil, nil, nil, nil, "p", "n"],
    ["B", "P", nil, nil, nil, nil, "p", "b"],
    ["Q", "P", nil, nil, nil, nil, "p", "q"],
    ["K", "P", nil, nil, nil, nil, "p", "k"],
    ["B", "P", nil, nil, nil, nil, "p", "b"],
    ["N", "P", nil, nil, nil, nil, "p", "n"],
    ["R", "P", nil, nil, nil, nil, "p", "r"],
  ]

  FILE_TO_INDEX = {
    'a' => 0,
    'b' => 1,
    'c' => 2,
    'd' => 3,
    'e' => 4,
    'f' => 5,
    'g' => 6,
    'h' => 7,
  }
  INDEX_TO_FILE = Hash[FILE_TO_INDEX.map(&:reverse)]

  RANK_TO_INDEX = {
    '1' => 0,
    '2' => 1,
    '3' => 2,
    '4' => 3,
    '5' => 4,
    '6' => 5,
    '7' => 6,
    '8' => 7,
  }
  INDEX_TO_RANK = Hash[RANK_TO_INDEX.map(&:reverse)]

  # algebraic to unicode piece lookup
  #
  UNICODE_PIECES = {
    'k' => "\u{265A}",
    'q' => "\u{265B}",
    'r' => "\u{265C}",
    'b' => "\u{265D}",
    'n' => "\u{265E}",
    'p' => "\u{265F}",
    'K' => "\u{2654}",
    'Q' => "\u{2655}",
    'R' => "\u{2656}",
    'B' => "\u{2657}",
    'N' => "\u{2658}",
    'P' => "\u{2659}",
    nil => '_',
  }

  attr_accessor :squares

  # @return [PGN::Board] a board in the starting position
  #
  def self.start
    PGN::Board.new(START)
  end

  # @param squares [<Array<Array<String>>>] the squares of the board
  # @example
  #   PGN::Board.new(
  #     [
  #       ["R", "P", nil, nil, nil, nil, "p", "r"],
  #       ["N", "P", nil, nil, nil, nil, "p", "n"],
  #       ["B", "P", nil, nil, nil, nil, "p", "b"],
  #       ["Q", "P", nil, nil, nil, nil, "p", "q"],
  #       ["K", "P", nil, nil, nil, nil, "p", "k"],
  #       ["B", "P", nil, nil, nil, nil, "p", "b"],
  #       ["N", "P", nil, nil, nil, nil, "p", "n"],
  #       ["R", "P", nil, nil, nil, nil, "p", "r"],
  #     ]
  #   )
  #
  def initialize(squares)
    self.squares = squares
  end

  # @overload at(str)
  #   Looks up a piece based on the string representation of a square (e4)
  #   @param str [String] the square in algebraic notation
  # @overload at(file, rank)
  #   Looks up a piece based on zero-indexed coordinates (4, 3)
  #   @param file [Integer] the file the piece is on
  #   @param rank [Integer] the rank the piece is on
  # @return [String, nil] the piece on the square, or nil if it is
  #   empty
  # @example
  #   board.at(4,3)  #=> "P"
  #   board.at("e4") #=> "P"
  #
  def at(*args)
    case args.length
    when 1
      self.at(*coordinates_for(args.first))
    when 2
      self.squares[args[0]][args[1]]
    end
  end

  # @param changes [Hash<String, <String, nil>>] changes to make to the board
  # @return [self]
  # @example
  #   board.change!({"e2" => nil, "e4" => "P"})
  #
  def change!(changes)
    changes.each do |square, piece|
      self.update(square, piece)
    end
    self
  end

  # @param square [String] the square in algebraic notation
  # @param piece [String, nil] the piece to put on the square
  # @return [self]
  # @example
  #   board.update("e4", "P")
  #
  def update(square, piece)
    coords = coordinates_for(square)
    self.squares[coords[0]][coords[1]] = piece
    self
  end

  # @param position [String] the square in algebraic notation
  # @return [Array<Integer>] the coordinates of the square
  # @example
  #   board.coordinates_for("e4") #=> [4, 3]
  #
  def coordinates_for(position)
    file_chr, rank_chr = position.chars.to_a
    file = FILE_TO_INDEX[file_chr]
    rank = RANK_TO_INDEX[rank_chr]
    [file, rank]
  end

  # @param coordinates [Array<Integer>] the coordinates of the square
  # @return [String] the square in algebraic notation
  # @example
  #   board.position_for([4, 3]) #=> "e4"
  #
  def position_for(coordinates)
    file, rank = coordinates
    file_chr = INDEX_TO_FILE[file]
    rank_chr = INDEX_TO_RANK[rank]
    [file_chr, rank_chr].join('')
  end

  # @return [String] the board in human readable format with unicode
  #   pieces
  #
  def inspect
    self.squares.transpose.reverse.map do |row|
      row.map{|chr| UNICODE_PIECES[chr] }.join(' ')
    end.join("\n")
  end

  # @return [PGN::Board] a copy of self with duplicated squares
  #
  def dup
    PGN::Board.new(self.squares.map(&:dup))
  end

end

    		
  





    
  



  

    
Class Method Details


    
      

  

  
    .start  ⇒ PGN::Board 
  

  

  




  

    

Returns a board in the starting position.



  





  

Returns:


    
  
    
  • 
      
      
        (PGN::Board)
      
      
      
        —
        
    

    a board in the starting position
    

    
      
    
    • 
  





  

    
      


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# File 'lib/pgn/board.rb', line 72

def self.start
  PGN::Board.new(START)
end

    		
  





    
  


  

    
Instance Method Details


    
      

  

  
    
      #at(str)  ⇒ String? 
    
      #at(file, rank)  ⇒ String? 
    
  

  

  




  

    

Returns the piece on the square, or nil if it is empty.



  





  
  

    
Examples:

    
      
      
board.at(4,3)  #=> "P"
board.at("e4") #=> "P"

    
  


  
Overloads:

  
    
    
      
      
  • 
        #at(str)  ⇒ String? 
        
    
  
    
    

    Looks up a piece based on the string representation of a square (e4)
    


  
    

    

    
  
    Parameters:
    

      
  
    
    • 
      
        str
      
      
        (String)
      
      
      
        —
        
      

      the square in algebraic notation
      

      
      
    
      • 
  

    



    
      
    • 
    
      
      
  • 
        #at(file, rank)  ⇒ String? 
        
    
  
    
    

    Looks up a piece based on zero-indexed coordinates (4, 3)
    


  
    

    

    
  
    Parameters:
    

      
  
    
    • 
      
        file
      
      
        (Integer)
      
      
      
        —
        
      

      the file the piece is on
      

      
      
    
      • 
  
    
    • 
      
        rank
      
      
        (Integer)
      
      
      
        —
        
      

      the rank the piece is on
      

      
      
    
      • 
  

    



    
      
    • 
    
  



Returns:


    
  
    
  • 
      
      
        (String, nil)
      
      
      
        —
        
    

    the piece on the square, or nil if it is empty
    

    
      
    
    • 
  





  

    
      


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# File 'lib/pgn/board.rb', line 108

def at(*args)
  case args.length
  when 1
    self.at(*coordinates_for(args.first))
  when 2
    self.squares[args[0]][args[1]]
  end
end

    		
  





    
      

  

  
    #change!(changes)  ⇒ self 
  

  

  




  

    

  





  
  

    
Examples:

    
      
      
board.change!({"e2" => nil, "e4" => "P"})

    
  


Parameters:


    
  
    
  • 
      
        changes
      
      
        (Hash<String, <String, nil>>)
      
      
      
        —
        
    

    changes to make to the board
    

    
      
    
    • 
  




Returns:


    
  
    
  • 
      
      
        (self)
      
      
      
    
    • 
  





  

    
      


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# File 'lib/pgn/board.rb', line 122

def change!(changes)
  changes.each do |square, piece|
    self.update(square, piece)
  end
  self
end

    		
  





    
      

  

  
    #coordinates_for(position)  ⇒ Array<Integer> 
  

  

  




  

    

Returns the coordinates of the square.



  





  
  

    
Examples:

    
      
      
board.coordinates_for("e4") #=> [4, 3]

    
  


Parameters:


    
  
    
  • 
      
        position
      
      
        (String)
      
      
      
        —
        
    

    the square in algebraic notation
    

    
      
    
    • 
  




Returns:


    
  
    
  • 
      
      
        (Array<Integer>)
      
      
      
        —
        
    

    the coordinates of the square
    

    
      
    
    • 
  





  

    
      


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# File 'lib/pgn/board.rb', line 146

def coordinates_for(position)
  file_chr, rank_chr = position.chars.to_a
  file = FILE_TO_INDEX[file_chr]
  rank = RANK_TO_INDEX[rank_chr]
  [file, rank]
end

    		
  





    
      

  

  
    #dup  ⇒ PGN::Board 
  

  

  




  

    

Returns a copy of self with duplicated squares.



  





  

Returns:


    
  
    
  • 
      
      
        (PGN::Board)
      
      
      
        —
        
    

    a copy of self with duplicated squares
    

    
      
    
    • 
  





  

    
      


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# File 'lib/pgn/board.rb', line 176

def dup
  PGN::Board.new(self.squares.map(&:dup))
end

    		
  





    
      

  

  
    #inspect  ⇒ String 
  

  

  




  

    

Returns the board in human readable format with unicode pieces.



  





  

Returns:


    
  
    
  • 
      
      
        (String)
      
      
      
        —
        
    

    the board in human readable format with unicode pieces
    

    
      
    
    • 
  





  

    
      


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# File 'lib/pgn/board.rb', line 168

def inspect
  self.squares.transpose.reverse.map do |row|
    row.map{|chr| UNICODE_PIECES[chr] }.join(' ')
  end.join("\n")
end

    		
  





    
      

  

  
    #position_for(coordinates)  ⇒ String 
  

  

  




  

    

Returns the square in algebraic notation.



  





  
  

    
Examples:

    
      
      
board.position_for([4, 3]) #=> "e4"

    
  


Parameters:


    
  
    
  • 
      
        coordinates
      
      
        (Array<Integer>)
      
      
      
        —
        
    

    the coordinates of the square
    

    
      
    
    • 
  




Returns:


    
  
    
  • 
      
      
        (String)
      
      
      
        —
        
    

    the square in algebraic notation
    

    
      
    
    • 
  





  

    
      


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# File 'lib/pgn/board.rb', line 158

def position_for(coordinates)
  file, rank = coordinates
  file_chr = INDEX_TO_FILE[file]
  rank_chr = INDEX_TO_RANK[rank]
  [file_chr, rank_chr].join('')
end

    		
  





    
      

  

  
    #update(square, piece)  ⇒ self 
  

  

  




  

    

  





  
  

    
Examples:

    
      
      
board.update("e4", "P")

    
  


Parameters:


    
  
    
  • 
      
        square
      
      
        (String)
      
      
      
        —
        
    

    the square in algebraic notation
    

    
      
    
    • 
  
    
  • 
      
        piece
      
      
        (String, nil)
      
      
      
        —
        
    

    the piece to put on the square
    

    
      
    
    • 
  




Returns:


    
  
    
  • 
      
      
        (self)
      
      
      
    
    • 
  





  

    
      


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# File 'lib/pgn/board.rb', line 135

def update(square, piece)
  coords = coordinates_for(square)
  self.squares[coords[0]][coords[1]] = piece
  self
end