Class: PGN::Board
- Inherits:
-
Object
- Object
- PGN::Board
- 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'] ].freeze
- FILE_TO_INDEX =
('a'..'h').each_with_index.to_h
- INDEX_TO_FILE =
FILE_TO_INDEX.map(&:reverse).to_h
- RANK_TO_INDEX =
('1'..'8').each_with_index.to_h
- INDEX_TO_RANK =
RANK_TO_INDEX.map(&:reverse).to_h
- 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 => '_' }.freeze
Instance Attribute Summary collapse
-
#squares ⇒ Array<Array<String>>
The pieces on the board.
Class Method Summary collapse
-
.start ⇒ PGN::Board
A board in the starting position.
Instance Method Summary collapse
-
#at(*args) ⇒ String?
The piece on the square, or nil if it is empty.
- #change!(changes) ⇒ self
-
#coordinates_for(position) ⇒ Array<Integer>
The coordinates of the square.
-
#dup ⇒ PGN::Board
A copy of self with duplicated squares.
-
#initialize(squares) ⇒ Board
constructor
A new instance of Board.
-
#inspect ⇒ String
The board in human readable format with unicode pieces.
-
#position_for(coordinates) ⇒ String
The square in algebraic notation.
- #update(square, piece) ⇒ self
Constructor Details
#initialize(squares) ⇒ Board
Returns a new instance of Board.
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# File 'lib/pgn/board.rb', line 74 def initialize(squares) self.squares = squares end |
Instance Attribute Details
#squares ⇒ Array<Array<String>>
Returns the pieces on the board.
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# File 'lib/pgn/board.rb', line 13 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'] ].freeze FILE_TO_INDEX = ('a'..'h').each_with_index.to_h INDEX_TO_FILE = FILE_TO_INDEX.map(&:reverse).to_h RANK_TO_INDEX = ('1'..'8').each_with_index.to_h INDEX_TO_RANK = RANK_TO_INDEX.map(&:reverse).to_h # 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 => '_' }.freeze 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 at(*coordinates_for(args.first)) when 2 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| 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) 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 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(squares.map(&:dup)) end end |
Class Method Details
.start ⇒ PGN::Board
Returns a board in the starting position.
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# File 'lib/pgn/board.rb', line 55 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.
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# File 'lib/pgn/board.rb', line 91 def at(*args) case args.length when 1 at(*coordinates_for(args.first)) when 2 squares[args[0]][args[1]] end end |
#change!(changes) ⇒ self
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# File 'lib/pgn/board.rb', line 105 def change!(changes) changes.each do |square, piece| update(square, piece) end self end |
#coordinates_for(position) ⇒ Array<Integer>
Returns the coordinates of the square.
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# File 'lib/pgn/board.rb', line 129 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.
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# File 'lib/pgn/board.rb', line 159 def dup PGN::Board.new(squares.map(&:dup)) end |
#inspect ⇒ String
Returns the board in human readable format with unicode pieces.
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# File 'lib/pgn/board.rb', line 151 def inspect 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.
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# File 'lib/pgn/board.rb', line 141 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
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# File 'lib/pgn/board.rb', line 118 def update(square, piece) coords = coordinates_for(square) squares[coords[0]][coords[1]] = piece self end |