野牛的ANTLR语法 [英] ANTLR grammar from bison

问题描述

我正在尝试将野牛语法转换为ANTLR.语法本身在野牛中非常简单，但我找不到实现此目的的简单方法.

I'm trying to translate a grammar from bison to ANTLR. The grammar itself is pretty simple in bison but I cannot find a simple way for doing this.

野牛语法:

expr = expr or expr | expr and expr | (expr)

欢迎使用任何提示/链接/指针.

Any hints/links/pointers are welcome.

谢谢， 尤利安

推荐答案

在ANTLR中，您无法创建左递归规则:

In ANTLR, you cannot create left recursive rules:

a : a b
  ;

尾递归很好:

a : b a
  ;

有关左递归规则的更多信息，请参见 ANTLR的Wiki .

For more information on left recursive rules, see ANTLR's Wiki.

因此，您的示例如下所示:

So, your example could look like:

parse
  :  expr+ EOF
  ;

expr
  :  orExpr
  ;

orExpr
  :  andExpr ('or' andExpr)*
  ;

andExpr
  :  atom ('and' atom)*
  ;

atom
  :  Boolean
  |  '(' expr ')'
  ;

Boolean
  :  'true'
  |  'false'
  ;

这是Java中的一个小演示:

Here's a small demo in Java:

grammar BoolExp;

@members {
  public static void main(String[] args) throws Exception {
    if(args.length != 1) {
      System.out.println("Usage:");
      System.out.println(" - Windows    : java -cp .:antlr-3.2.jar BoolExpParser \"EXPRESSION\"");
      System.out.println(" - *nix/MacOS : java -cp .;antlr-3.2.jar BoolExpParser \"EXPRESSION\"");
      System.exit(0);
    }
    ANTLRStringStream in = new ANTLRStringStream(args[0]);
    BoolExpLexer lexer = new BoolExpLexer(in);
    CommonTokenStream tokens = new CommonTokenStream(lexer);
    BoolExpParser parser = new BoolExpParser(tokens);
    parser.parse();
  }
}

parse
  :  e=expr EOF {System.out.println($e.bool);}
  ;

expr returns [boolean bool]
  :  e=orExpr {$bool = $e.bool;}
  ;

orExpr returns [boolean bool]
  :  e1=andExpr       {$bool = $e1.bool;} 
     ('or' e2=andExpr {$bool = $bool || $e2.bool;}
     )*
  ;

andExpr returns [boolean bool]
  :  e1=atom        {$bool = $e1.bool;} 
     ('and' e2=atom {$bool = $bool && $e2.bool;}
     )*
  ;

atom returns [boolean bool]
  :  b=Boolean      {$bool = new Boolean($b.text).booleanValue();}
  |  '(' e=expr ')' {$bool = $e.bool;}
  ;

Boolean
  :  'true'
  |  'false'
  ;

Space
  :  (' ' | '\t' | '\n' | '\r') {skip();}
  ;

首先创建一个词法分析器&解析器(1)，然后编译所有源文件(2).最后，执行BoolExpParser类(3).

First create a lexer & parser (1) and then compile all source files (2). Finally, execute the BoolExpParser class (3).

// Windows & *nix/MacOS
java -cp antlr-3.2.jar org.antlr.Tool BoolExp.g

2

// Windows
javac -cp .;antlr-3.2.jar *.java

// *nix/MacOS
javac -cp .:antlr-3.2.jar *.java

3

// Windows
java -cp .;antlr-3.2.jar BoolExpParser "false and true or true"

// *nix/MacOS
java -cp .:antlr-3.2.jar BoolExpParser "false and true or true"

Terence Parr 的 Scott 创建了一些出色的视频教程(在ANTLR 3上使用Eclipse).

Terence Parr's ANTLR reference is the book on ANTLR. And Scott created some excellent video tutorials on ANTLR 3 (with Eclipse).

这篇关于野牛的ANTLR语法的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！