Parsing Chess PGN files with ANTLR4 (in Java) : error on my own grammar.

[laurent bernabe]

Hello everyone,

I wrote a simple grammar in order to parse PGN files (file is attached to this message).

But I got the following error :

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error(50): /home/my_path/Pgn.g4:6:6: syntax error: 'TAG_TYPE "TAG_VALUE"' came as a complete surprise to me while matching alternative

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I guess it is because I am using [, ] and " in a grammar definition : so how can I solve the problem (I've tried to backslash thoses, but I got an exception when generating the grammar with antlr4 command).

Thanks in advance for helps and suggestions.

Regards

[laurent bernabe]

I've tried to solve the problem, putting [ in string litterals :

-------------------------------------------------------------------------------------------

grammar Pgn;

file: game (NEWLINE+ game)*;

game: (tag+ NEWLINE+)? notation;

tag: '['TAG_TYPE "TAG_VALUE"']';

notation: move+ END_RESULT?;

move: MOVE_NUMBER\. MOVE_DESC MOVE_DESC #CompleteMove

| MOVE_NUMBER\. MOVE_DESC #OnlyWhiteMove

| MOVE_NUMBER\.\.\. MOVE_DESC #OnlyBlackMove

;

END_RESULT: '1-0'

| '0-1'

| '1/2-1/2'

;

TAG_TYPE: LETTER+;

TAG_VALUE: .*;

MOVE_NUMBER: DIGIT+;

MOVE_DESC: .*;

NEWLINE: \r? \n;

SPACES: [ \t]+ -> skip;

fragment LETTER: [a-zA-Z];

fragment DIGIT: [0-9];

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But this time a get a stacktrace error :

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$ antlr4 Pgn.g4 

org\antlr\v4\parse\GrammarTreeVisitor.g: node from line 24:11 required (...)+ loop did not match anything at input 'r'

org\antlr\v4\parse\GrammarTreeVisitor.g: node from line 24:15 mismatched tree node: n expecting <UP>

org\antlr\v4\parse\GrammarTreeVisitor.g: node from line 24:11 required (...)+ loop did not match anything at input 'r'

org\antlr\v4\parse\GrammarTreeVisitor.g: node from line 24:15 mismatched tree node: n expecting <UP>

org\antlr\v4\parse\GrammarTreeVisitor.g: node from line 24:11 required (...)+ loop did not match anything at input 'r'

org\antlr\v4\parse\GrammarTreeVisitor.g: node from line 24:15 mismatched tree node: n expecting <UP>

org\antlr\v4\parse\GrammarTreeVisitor.g: node from line 24:11 required (...)+ loop did not match anything at input 'r'

org\antlr\v4\parse\GrammarTreeVisitor.g: node from line 24:15 mismatched tree node: n expecting <UP>

error(20):  internal error: Rule LETTER undefined 

error(20):  internal error: element list has first|last == null 

Exception in thread "main" java.lang.NullPointerException

at org.antlr.v4.automata.ParserATNFactory.elemList(ParserATNFactory.java:445)

at org.antlr.v4.automata.ParserATNFactory.alt(ParserATNFactory.java:414)

at org.antlr.v4.parse.ATNBuilder.alternative(ATNBuilder.java:567)

at org.antlr.v4.parse.ATNBuilder.block(ATNBuilder.java:400)

at org.antlr.v4.parse.ATNBuilder.subrule(ATNBuilder.java:1185)

at org.antlr.v4.parse.ATNBuilder.element(ATNBuilder.java:887)

at org.antlr.v4.parse.ATNBuilder.alternative(ATNBuilder.java:550)

at org.antlr.v4.parse.ATNBuilder.ruleBlock(ATNBuilder.java:289)

at org.antlr.v4.automata.ParserATNFactory._createATN(ParserATNFactory.java:148)

at org.antlr.v4.automata.LexerATNFactory.createATN(LexerATNFactory.java:94)

at org.antlr.v4.Tool.processNonCombinedGrammar(Tool.java:407)

at org.antlr.v4.Tool.process(Tool.java:376)

at org.antlr.v4.Tool.processGrammarsOnCommandLine(Tool.java:343)

at org.antlr.v4.Tool.main(Tool.java:190)_______________________________________________________

Regards

[laurent bernabe]

Got an answer an stackoveflow :)

here