This repository aims to generate an analyzer to read chess files in PGN format. It supports one or more moves, ending with a score, such as "1. e4 e5 ... 0-1", but also long formats: "1. d2d4 Ng8f6", the classic castling "OO oo" but also "e1g1 e8g8" , supports parsing of headers and comments.

PGN is the de-facto standard for chess games, especially when it comes to interoperability. Unfortunately, PGN is somewhat misdesigned. Apparently, it’s not just me who thinks so. PGN is designed to make it easy for humans to read PGN files, and edit or write them manually with a text editor. At a cost, namely that it’s difficult to parse it with computers.

The odd thing here is that PGN files are rarely created manually, almost everyone uses a chess program to enter or edit moves, and then save the game afterwards. That’s the basic mis-design.

The main difficulty in parsing PGN files – aside from a lot of ambiguities – is SAN notation, i.e. the source-field of a move is missing. For a human it’s easy to spot the source-field, but for a computer it means that the program has to know the chess-rules to figure out which move is executed .

This parser was generated by using canopy a PEG (Parsing Expression Grammars) parser compiler.

Why did I decide to use a PEG parser?

Because it has several advantages:

1. I can generate the parser for Python, Ruby, Java and JS
2. I have to developed just 50% more of the parser
3. Surely my knowledge of PEG Parsers will should important for my next homework: a pattern language for chess.

Status:

Python Parser : 100% Ruby Parser : 95% Java Parser : 50% Js Parser : 50%

Usage example (Ruby):

test.rb

$LOAD_PATH << '.'

require 'parser' require_relative 'pgn'

include PGN

options = { actions: Actions.new, types: nil } file_data = File.open("kasparov.pgn", :encoding => 'ISO-8859-1').read game = PGN::parse(file_data, options ) #game = PGN::parse("1. c2c4 { Comments by/Kommentare von: GM Gerald Hertneck } 1... c7c6 2. d2d4 d7d5", options ) puts game.move(1) puts game.move(1).black.san puts game.movetext puts game.tag_pairs puts game.score

Execution:

➜ ruby git:(master) ✗ ruby test.rb

1. c4 c6

2. c4 c6

3. d4 d5

4. Nf3 Nf6

5. Qc2 dxc4

6. Qxc4 Bf5

7. Nc3 Nbd7

8. g3 e6

9. Bg2 Be7

10. O-O O-O

11. e3 Ne4

12. Qe2 Qb6

13. Rd1 Rad8

14. Ne1 Ndf6

15. Nxe4 Nxe4

16. f3 Nd6

17. a4 Qb3

18. e4 Bg6

19. Rd3 Qb4

20. b3 Nc8

21. Nc2 Qb6

22. Bf4 c5

23. Be3 cxd4

24. Nxd4 Bc5

25. Rad1 e5

26. Nc2 Rxd3

27. Qxd3 Ne7

28. b4 Bxe3+

29. Qxe3 Rd8

30. Rxd8+ Qxd8

31. Bf1 b6

32. Qc3 f6

33. Bc4+ Bf7

34. Ne3 Qd4

35. Bxf7+ Kxf7

36. Qb3+ Kf8

37. Kg2 Qd2+

38. Kh3 Qe2

39. Ng2 h5

40. Qe3 Qc4

41. Qd2 Qe6+

42. g4 hxg4

43. fxg4 Qc4

44. Qe1 Qb3+

45. Ne3 Qd3

46. Kg3 Qxe4

47. Qd2 Qf4+

48. Kg2 Qd4

49. Qxd4 exd4

50. Nc4 Nc6

51. b5 Ne5

52. Nd6 d3

53. Kf2 Nxg4+

54. Ke1 Nxh2

55. Kd2 Nf3+

56. Kxd3 Ke7

57. Nf5+ Kf7

58. Ke4 Nd2+

59. Kd5 g5

60. Nd6+ Kg6

61. Kd4 Nb3+ Event London PCA/Intel-GP Site London ENG Date 1994.08.31 EventDate ? Round 1 Result 0-1 White Garry Kasparov Black Chess Genius (Computer) ECO D11 WhiteElo ? BlackElo ? PlyCount 120 0-1

Any help is wellcome!

Canopy

Canopy is a parser compiler targeting Java, JavaScript, Python and Ruby. It takes a file describing a parsing expression grammar and compiles it into a parser module in the target language. The generated parsers have no runtime dependency on Canopy itself.

For usage documentation see canopy.jcoglan.com.

https://blog.jcoglan.com/2015/07/19/canopy-produces-portable-peg-parsers/https://github.com/jcoglan/canopy