ast生成时antlr 4.7错误

Question

我正在尝试运行按照 - http://meri-stuff.blogspot.com/2011/08/antlr-tutorial-hello-word.html

的步骤说明进行 strp

根据上述网页的原始代码 -

public CommonTree compile(String expression) {
try {
  //lexer splits input into tokens
  ANTLRStringStream input = new ANTLRStringStream(expression);
  TokenStream tokens = new CommonTokenStream( new S001HelloWordLexer( input ) );

  //parser generates abstract syntax tree
  S001HelloWordParser parser = new S001HelloWordParser(tokens);
  S001HelloWordParser.expression_return ret = parser.expression();

  //acquire parse result
  CommonTree ast = (CommonTree) ret.tree;
  printTree(ast);
  return ast;
} catch (RecognitionException e) {
  throw new IllegalStateException("Recognition exception is never thrown, only declared.");
}
}

我修改了下面部分代码：

public CommonTree compile(String expression) {
    try {
      //lexer splits input into tokens
      ANTLRStringStream input = new ANTLRStringStream(expression);
      TokenStream tokens = new CommonTokenStream( (TokenSource) new S001HelloWordLexer( (CharStream) input ) );

      //parser generates abstract syntax tree
      S001HelloWordParser parser = new S001HelloWordParser((org.antlr.v4.runtime.TokenStream) tokens);
      S001HelloWordParser.expression_return ret = parser.expression();

      //acquire parse result
      CommonTree ast = (CommonTree) ret.tree;
      printTree(ast);
      return ast;
    } catch (RecognitionException e) {
      throw new IllegalStateException("Recognition exception is never thrown, only declared.");
  }
}

问题出在我的 S001HelloWordParser 文件中，没有像 expression() 这样的方法，也没有静态 class 名称 'expression_return'，所以我无法创建变量 'ret' 我可以对谁调用 tree() 方法。我在这里缺少什么吗？

我还能如何生成树？或者对使用 antlr 4.7 版本的过程有什么想法吗？

请帮忙。谢谢！

Answer 1

I am trying to run strp by step instruction as per - http://meri-stuff.blogspot.com/2011/08/antlr-tutorial-hello-word.html

不要。那个教程是关于 ANTLR 3 的，你需要找一个 ANTLR 4 教程。

The issue is in my S001HelloWordParser file, there is no method as expression() nor is there a static class names 'expression_return'

这意味着您的 S001HelloWord 语法不包含名为 expression 的解析器规则。

从源头开始：https://github.com/antlr/antlr4/blob/master/doc/getting-started.md

这是关于 ANTLR4 表达式解析器的问答（包含完整代码示例）：If/else statements in ANTLR using listeners

ast生成时antlr 4.7错误

antlr 4.7 error while ast generation

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abstract-syntax-tree

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antlr4