如何访问 ANTLR 词法分析器的标记

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英文:

How to access ANTLR lexer tokens

问题

我已经指定了以下的ANTLR语法:

expression: ...
          | extractor=EXTRACTOR '(' setElementDefinition ',' expression ')' #setExtractorExp
          | ... ;

EXTRACTOR: 'select'
         | 'choose' ;

我想知道在解析这个表达式时我正在处理哪种类型的提取。一种方法是将提取器字段与包含提取器类型的字符串进行比较,就像这样:

@Override
public Expression visitSetExtractorExp(MyParser.SetExtractorExpContext ctx) {
    if(ctx.extractor.getText().equals("select")) { ... }
}

但我不想在这里重复提取器的名称,以防以后选择更改提取器的名称。所以有没有一种方法可以访问词法分析器的标记?

我想象中的写法类似于 if(ctx.extractor == MyLexer.EXTRACTOR.choose)

英文:

I have specified the following ANTLR grammar:

expression: ...
          | extractor=EXTRACTOR '(' setElementDefinition ',' expression ')' #setExtractorExp
          | ... ;

EXTRACTOR: 'select'
         | 'choose' ;

I would like to know which type of extraction I am dealing with when parsing this expression.
One way of doing it is by comparing the extractor field with a string containing the extractor type, like this:

@Override
public Expression visitSetExtractorExp(MyParser.SetExtractorExpContext ctx) {
    if(ctx.extractor.getText().equals("select")) { ... }
}

But I don't like to duplicate the names of the extractors here, in case I choose to change the names of the extractors later.
So is there a way to access the lexer tokens?

I am imagining something like if(ctx.extractor == MyLexer.EXTRACTOR.choose).

答案1

得分: 2

目前,您的 EXTRACTOR 只有一种类型,使得 "select""choose" 几乎是相同的。唯一区分它们的方式是像您已经在做的那样进行字符串比较。如果您不想这样做,可以像这样进行处理:

expression
 : ...
 | extractor '(' setElementDefinition ',' expression ')' #setExtractorExp
 | ... 
 ;

extractor
 : SELECT
 | CHOOSE
 ;

SELECT : 'select';
CHOOSE : 'choose';

并在您的访问者中:

@Override
public Expression visitSetExtractorExp(MyParser.SetExtractorExpContext ctx) {
  if(ctx.extractor().start.getType() == MyLexer.SELECT) { ... }
  else if(ctx.extractor().start.getType() == MyLexer.CHOOSE) { ... }
}

这样您就不需要复制(魔术)字符串。

英文:

Right now, your EXTRACTOR has just a single type, making "select" and "choose" pretty much the same. The only way to make a distinction is to to string comparison like you're already doing. If you don't want that, do something like this:

expression
 : ...
 | extractor '(' setElementDefinition ',' expression ')' #setExtractorExp
 | ... 
 ;

extractor
 : SELECT
 | CHOOSE
 ;

SELECT : 'select';
CHOOSE : 'choose';

and in your visitor:

@Override
public Expression visitSetExtractorExp(MyParser.SetExtractorExpContext ctx) {
  if(ctx.extractor().start.getType() == MyLexer.SELECT) { ... }
  else if(ctx.extractor().start.getType() == MyLexer.CHOOSE) { ... }
}

That way you don't have to duplicate (magic) strings.

huangapple
  • 本文由 发表于 2020年9月18日 18:58:38
  • 转载请务必保留本文链接:https://go.coder-hub.com/63954438.html
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