Games::Goban - Board for playing go, renju, othello, etc.


version 1.102


  use Games::Goban;
  my $board = new Games::Goban ( 
    size  => 19,
    game  => "go",
    white => "Seigen, Go",
    black => "Minoru, Kitani",
    referee => \&Games::Goban::Rules::Go,

  $board->move("pd"); $board->move("dd");
  print $board->as_sgf;


This is a generic module for handling goban-based board games. Theoretically, it can be used to handle many of the other games which can use Smart Game Format (SGF) but I want to keep it reasonably restricted in order to keep it simple.



Creates and initializes a new goban. The options and their legal values (* marks defaults):

  size       Any integer between 5 and 26, default: 19
  game       *go, othello, renju, gomoku
  white      Any text, default: "Miss White"
  black      Any text, default: "Mr Black"
  skip_i     Truth value; whether 'i' should be skipped; false by default
  referee    Any subroutine, default: sub {1} # (All moves are valid) 

The referee subroutine takes a board object and a piece object, and determines whether or not the move is legal. It also reports if the game is won.


    $ok = $board->move($position)

Takes a move, creates a Games::Goban::Piece object, and attempts to place it on the board, subject to the constraints of the referee. If this is not successful, it returns 0 and sets $@ to be an error message explaining why the move could not be made. If successful, updates the board, updates the move number and the turn, and returns true.


This method causes the current player to pass. At present, nothing happens for two subsequent passes.


    $move = $board->get($position)

Gets the Games::Goban::Piece object at the given location, if there is one. Locations are specified as per SGF - a 19x19 board starts from aa in the top left corner, with ss in the bottom right. (If the skip_i option was set while creating the board, tt is the bottom right and there are no i positions. This allows for traditional notation.)


    $size = $board->size

Returns the size of the goban.


  @hoshi_points = $board->hoshi

Returns a list of hoshi points.


  $star = $board->is_hoshi('dp')

Returns true if the named position is a hoshi (star) point.


    $sgf = $board->as_sgf;

Returns a representation of the board as an SGF (Smart Game Format) file.


    print $board->as_text(coords => 1)

Returns a printable text picture of the board, similar to that printed by gnugo. Black pieces are represented by X, white pieces by O, and the latest move is enclosed in parentheses. hoshi points are in their normal position for Go, and printed as an +. Coordinates are not printed by default, but can be enabled as suggested in the synopsis.


    my $key = $board->register(\&callback);

Register a callback to be called after every move is made. This is useful for analysis programs which wish to maintain statistics on the board state. The key returned from this can be fed to...


    $board->notes($key)->{score} += 5;

notes returns a hash reference which can be used by a callback to store local state about the board.


    $hash = $board->hash

Provides a unique hash of the board position. If the phrase "positional superko" means anything to you, you want to use this method. If not, move along, nothing to see here.


This method returns true if the 'skip_i' argument to the constructor was true and the 'i' coordinant should be skipped. (Note that 'i' is never skipped when producing SGF output.)

Games::Goban::Piece methods

Here are the methods which can be called on a Games::Goban::Piece object, representing a piece on the board.


Returns "b" for a black piece and "w" for a white. colour is also provided for Anglophones.


Similar to the notes method on the board class, this provides a private area for callbacks to scribble on.


Returns the position of this piece, as a two-character string. Incidentally, try to avoid taking references to Piece objects, since this stops them being destroyed in a timely fashion. Use a position and get if you can get away with it, or take a weak reference if you're worried about the piece going away or being replaced by another one in that position.


Returns the move number on which this piece was played.


Returns the board object whence this piece came.


  • use Games::Goban::Board for game board

  • add <$board-pass>>

  • possibly enable <$board-move('')>> to pass

  • produce example referee

  • produce sample method for removing captured stones


Smart Game Format:


The US Go Association:


  • Simon Cozens

  • Ricardo SIGNES <>


This software is copyright (c) 2002 by Simon Cozens.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.