需要 Antlr 多余的谓词吗? [英] Antlr superfluous Predicate required?

问题描述

我有一个文件，我想忽略其中的一部分.在 Lexer 中，我使用门控语义谓词来避免为文件的无趣部分创建标记.我的规则类似于以下.

A: {!ignore}?=>'一种';START_忽略: 'foo' {ignore = true;跳过();};END_忽略:'oof'{忽略=假；跳过();};忽略:{忽略}?=>.{跳过();};

但是，除非我将 START 和 END 更改为也使用语义谓词(如下所示)，否则它不起作用..

A: {!ignore}?=>'一种';START_忽略:{真}?=>'foo' {忽略 = 真；跳过();};END_忽略:{真}?=>'oof' {忽略 = 假；跳过();};忽略:{忽略}?=>.{跳过();};

为什么我必须添加谓词?

我使用的是 antlr-3.4

解决方案

为什么我必须添加谓词?

你没有.至少，没有使用 ANTLR v3.3.我不知道如何你正在测试，但不要使用 ANTLRWorks 的解释器或 Eclipse ANTLR IDE 插件.总是从命令行做一个小测试.

语法T;@parser::members {public static void main(String[] args) 抛出异常 {TLexer lexer = new TLexer(new ANTLRStringStream("A foo A B C oof A"));TParser parser = new TParser(new CommonTokenStream(lexer));parser.parse();}}@lexer::members {私有布尔忽略 = 假；}解析:(t=.{System.out.printf("[\%02d] type=\%s text='\%s'\n", $t.getCharPositionInLine(), tokenNames[$t.type], $t.text);})* EOF;一种: {!ignore}?=>'一种';START_忽略: 'foo' {ignore = true;跳过();};END_忽略:'oof'{忽略=假；跳过();};忽略:{忽略}?=>.{跳过();};空间: ' ' {跳过();};

像这样运行:

java -cp antlr-3.3.jar org.antlr.Tool T.gjavac -cp antlr-3.3.jar *.javajava -cp .:antlr-3.3.jar TParser

将打印以下内容:

[00] type=A text='A'[16] type=A text='A'

即:从输入 "A foo ABC oof A" 如下:"foo ABC oof" 是 skipped.>

I have a file where I want to ignore parts of it. In the Lexer I use gated semantic predicates to avoid creating tokens for the uninteresting part of the file. My rules are similar to the following.

A 
: {!ignore}?=> 'A' 
;
START_IGNORE
: 'foo' {ignore = true; skip();}
;
END_IGNORE
: 'oof' {ignore = false; skip();}
;
IGNORE
: {ignore}?=> . {skip();}
;    

However unless I change START and END to also use semantic predicates (as below) it does not work..

A 
: {!ignore}?=> 'A' 
;
START_IGNORE
: {true}?=> 'foo' {ignore = true; skip();}
;
END_IGNORE
: {true}?=> 'oof' {ignore = false; skip();}
;    
IGNORE
: {ignore}?=> . {skip();}
;  

Why do I have to add the predicates?

EDIT: I am using antlr-3.4

解决方案

Why do I have to add the predicates?

You don't. At least, not using ANTLR v3.3. I don't know how exactly you're testing, but don't use ANTLRWorks' interpreter or the Eclipse ANTLR IDE plugin. Always do a little test from the command line.

grammar T;

@parser::members {
  public static void main(String[] args) throws Exception {
    TLexer lexer = new TLexer(new ANTLRStringStream("A foo A B C oof A"));
    TParser parser = new TParser(new CommonTokenStream(lexer));
    parser.parse();
  }
}

@lexer::members {
  private boolean ignore = false;
}

parse
 : (t=. 
     {System.out.printf("[\%02d] type=\%s text='\%s'\n", $t.getCharPositionInLine(), tokenNames[$t.type], $t.text);}
   )* EOF
 ;

A 
 : {!ignore}?=> 'A' 
 ;

START_IGNORE
 : 'foo' {ignore = true; skip();}
 ;

END_IGNORE
 : 'oof' {ignore = false; skip();}
 ;

IGNORE
 : {ignore}?=> . {skip();}
 ;    

SPACE
 : ' ' {skip();}
 ;

Run it like this:

java -cp antlr-3.3.jar org.antlr.Tool T.g
javac -cp antlr-3.3.jar *.java
java -cp .:antlr-3.3.jar TParser

which will print the following:

[00] type=A text='A'
[16] type=A text='A'

I.e.: from the input "A foo A B C oof A" the following: "foo A B C oof" is skipped.

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