Question

我为ANTLR4制作了自己的国际象棋PGN语法，但是我得到了一个java stacktrace错误：

Pgn.g4语法：

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];

这是错误输出：

$ 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)

那么，我的语法有什么问题？

（请注意，这篇文章可能比我在this post中公开的那篇文章更进一步，我的语法错误。）

Answer 1

有些事情出错：

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

为什么TAG_VALUE周围有双引号？如果您想匹配令牌TAG_VALUE：tag: '['TAG_TYPE TAG_VALUE ']';

，请删除引号

MOVE_NUMBER\. MOVE_DESC MOVE_DESC

如果你想匹配文字.（DOT），你需要在它周围加上引号（而不是逃避它！）：MOVE_NUMBER '.' MOVE_DESC MOVE_DESC

NEWLINE:    \r? \n;

同样，如果你想匹配文字，请在其周围加上引号：NEWLINE: '\r'? '\n';

TAG_VALUE: .*;  
...
MOVE_DESC: .*;

这些规则会吞噬整个输入流。您需要另一种方法来匹配标记值并移动描述，而不是现在。请勿使用.*。

修改

这是现有的PGN语法：https://github.com/antlr/grammars-v4/tree/master/pgn

Antlr4语法编译错误

1 个答案:

修改