PGN parsing bug in Winboard?

[Volker Pittlik]

Geschrieben von:/Posted by: Volker Pittlik at 26 September 2004 12:43:13:

From Kurt Utzinger's excellent site a commented PGN of
the first Leko-Kramnik game can be downloaded
http://www.utzingerk.com/wch_kramnik_leko.pgn.
When loading this game in Winboard an error window
pops up saying "Illegal move: 29... a7".
Scid imports the PGN without problems. I don't
know if this is an error.
The PGN in question:

29. a4 {
Played instantly by Leko.} (29. Rd2 {
Threat Rxd4 looks safer but Leko must have been playing for the win} 29... c3 (
29... Bf6 30. Rxd8+ Rxd8 31. Qc6 c3 32. a4 h6 33. a5 Rd2 34. a6 Bd4 (34... Ra2
35. Kf1 $1 c2 (35... Bd4 $2 36. Qe8+ Kh7 37. Qe4+ g6 38. Qxd4 c2 39. Qc3 $18)
36. a7 Rxa7 

Any opinions?
Volker

[Enrico Cardelli]

Geschrieben von:/Posted by: Enrico Cardelli at 27. September 2004 23:45:
Als Antwort auf:/In reply to: PGN parsing bug in Winboard? geschrieben von:/posted by: Volker Pittlik at 26 September 2004 12:43:13:

From Kurt Utzinger's excellent site a commented PGN of
the first Leko-Kramnik game can be downloaded
http://www.utzingerk.com/wch_kramnik_leko.pgn.
When loading this game in Winboard an error window
pops up saying "Illegal move: 29... a7".
Scid imports the PGN without problems. I don't
know if this is an error.
The PGN in question:

Any opinions?
Volker

>29. a4 {
>Played instantly by Leko.} (29. Rd2 {
>Threat Rxd4 looks safer but Leko must have been playing for the win} 29... c3 (
>29... Bf6 30. Rxd8+ Rxd8 31. Qc6 c3 32. a4 h6 33. a5 Rd2 34. a6 Bd4 (34... Ra2
>35. Kf1 $1 c2 (35... Bd4 $2 36. Qe8+ Kh7 37. Qe4+ g6 38. Qxd4 c2 39. Qc3 $18)
>36. a7 Rxa7 
>
I think this is not a real bug in Winboard pgn parsing, but simply a
limitation by the author in how deeply nested must be comments or variations.
I think that Winboard reads the open parentheses before 36. a7 as the end of
the variation, and try to resume the main line from there. Being the move not
legal, an error arises. If you ever took a look at winboard code, you'll see
that for move parsing is used a lex parser, and I know that it is not a simple
task to manage any kind of nesting with such a tool.
Bye, E.