Question

我正在尝试使用ANTLR在C＃中运行一个简单的计算器。我有一个简单的语法。问题是我的令牌流总是空出来，我不明白为什么。我已经摘录了我认为是下面的关键代码。我错过了什么？

SimpleCalc.g4：

 grammar SimpleCalc;

 options {
 language=CSharp2;
 }

 tokens {
     PLUS,
     MINUS, 
     TIMES,
     DIV
 }

@members {

}

expr    : term ( (PLUS|MINUS) term )* ;
term    : factor ( ( TIMES|DIV ) factor )* ;
factor  : NUMBER ;
DIV : '/';
PLUS : '+';
TIMES: '*';
MINUS: '-';

NUMBER : (DIGIT)+   {System.Console.WriteLine("Found number");  };
WHITESPACE: ( '\t' | ' ' | '\r' | '\n' | '\u000C' )+   -> skip ;
fragment DIGIT  : '0'..'9';

执行实际工作的方法，或尝试：

class Program {

  public static void Main(string[] args) {
    Run();
  }

  public static void Run() {

    try {
      Console.WriteLine("START");
      RunTestCalculator();
      Console.Write("DONE. Hit RETURN to exit: ");
    } catch (Exception ex) {
      Console.WriteLine("ERROR: " + ex);
      Console.Write("Hit RETURN to exit: ");
    }
    Console.ReadLine();
  }

  public static void RunTestCalculator() {
    AntlrInputStream inputStream = new AntlrInputStream(@" 9 + 3 ");
    SimpleCalcLexer lex = new SimpleCalcLexer(inputStream);
    CommonTokenStream tokens = new CommonTokenStream(lex);
    var t = tokens.Get(0);
    Console.WriteLine("t = " + t.ToString());
    SimpleCalcParser parser = new SimpleCalcParser(tokens);
    try {
      var theExpr = parser.expr();
      Console.WriteLine("found expr " + theExpr.ToString());
    } catch (RecognitionException e) {
      System.Console.WriteLine("EXCEPTION:");
      System.Console.WriteLine(e.StackTrace);
    }
  }
}

控制台输出证明上述方法正在执行，但令牌不包含任何内容：

START
ERROR: System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values.
Parameter name: token index 0 out of range 0..-1
   at Antlr4.Runtime.BufferedTokenStream.Get(Int32 i)
   at AntlerTest.Program.RunTestCalculator() in c:\Users\William\Documents\Visual Studio 2012\Projects\AntlerTest\AntlerTest\Program.cs:line 32
   at AntlerTest.Program.Run() in c:\Users\William\Documents\Visual Studio 2012\
Projects\AntlerTest\AntlerTest\Program.cs:line 19
Hit RETURN to exit:

Answer 1

我缺少的是令牌流在expr调用之前保持为空。当我在expr之后移动get调用时，令牌就在那里：

    public static void RunTestCalculator() {
        AntlrInputStream inputStream = new AntlrInputStream(@" 9 + 3 ");
        SimpleCalcLexer lex = new SimpleCalcLexer(inputStream);
        CommonTokenStream tokens = new CommonTokenStream(lex);
        SimpleCalcParser parser = new SimpleCalcParser(tokens);
        try {
            var theExpr = parser.expr();
            Console.WriteLine("found expr " + theExpr.ToString());
    var t = tokens.Get(0);
    Console.WriteLine("t = " + t.ToString());
        } catch (RecognitionException e) {
            System.Console.WriteLine("EXCEPTION:");
            System.Console.WriteLine(e.StackTrace);
        }
    }

输出：

START
Found number
Found number
found expr []
t = [@0,1:1='9',<5>,1:1]
DONE. Hit RETURN to exit:

ANTLR令牌流是空的 - 为什么？

1 个答案: