Question

标记可包含转义字符的引用字符串的常用方法是什么？以下是一些例子：

1) "this is good"
2) "this is\"good\""
3) "this \is good"
4) "this is bad\"
5) "this is \\"bad"
6) "this is bad
7)  this is bad"
8)  this is bad

下面是一个不能正常工作的示例解析器;除了成功解析的示例4和5之外，它有预期的结果。

options
{
  LOOKAHEAD = 3;
  CHOICE_AMBIGUITY_CHECK = 2;
  OTHER_AMBIGUITY_CHECK = 1;
  STATIC = false;
  DEBUG_PARSER = false;
  DEBUG_LOOKAHEAD = false;
  DEBUG_TOKEN_MANAGER = true;
  ERROR_REPORTING = true;
  JAVA_UNICODE_ESCAPE = false;
  UNICODE_INPUT = false;
  IGNORE_CASE = false;
  USER_TOKEN_MANAGER = false;
  USER_CHAR_STREAM = false;
  BUILD_PARSER = true;
  BUILD_TOKEN_MANAGER = true;
  SANITY_CHECK = true;
  FORCE_LA_CHECK = true;
}

PARSER_BEGIN(MyParser)
import java.io.ByteArrayInputStream;
import java.io.UnsupportedEncodingException;
public class MyParser {
    public static void main(String[] args) throws UnsupportedEncodingException, ParseException{
        //note that this conversion to an input stream is only good for small strings
        MyParser parser = new MyParser(new ByteArrayInputStream(args[0].getBytes("UTF-8")));
        parser.enable_tracing();
        parser.myProduction();
        System.out.println("Must have worked!");
    }
}
PARSER_END(MyParser)

TOKEN:
{
<QUOTED: 
    "\"" 
    (
        "\\" ~[]    //any escaped character
        |           //or
        ~["\""]      //any non-quote character
    )* 
    "\""
>
}


void myProduction() :
{}
{
    <QUOTED>
    <EOF>
}

您可以从命令行运行MyParser并输入解析。它将打印“必须有效！”如果它起作用，或者如果没有则抛出错误。

如何在示例4和5上更改此解析器以正确失败？

Answer 1

要修复正则表达式，请将其设为

TOKEN: {
<QUOTED: 
    "\"" 
    (
         "\\" ~[]     //any escaped character
    |                 //or
        ~["\"","\\"]  //any character except quote or backslash
    )* 
    "\"" > 
}

带有转义字符的JavaCC引用

1 个答案: