ANTLR Tree Grammar for loops

Question

我試圖通過直接閱讀treeWalker並實現編譯器所需的命令來實現解析器。所以，如果我有一個像這樣的命令：

statement 
      : 
      ^('WRITE' expression) 
      { 
       //Here is the command that is created by my Tree Parser 
       ch.emitRO("OUT",0,0,0,"write out the value of ac"); 
       //and then I handle it in my other classes 
      } 
; 

我希望它寫OUT 0,0,0;到一個文件。這是我的語法。

我有一個問題，但在我的語法環部分，它是：

'WHILE'^ expression 'DO' stat_seq 'ENDDO' 

，並在樹解析器：

doWhileStatement 
: 
^('WHILE' expression 'DO' stat_seq 'ENDDO') 
; 

我想要做的是直接解析從代碼while循環進入我需要的命令。我想出了這個解決方案，但它不工作：

doWhileStatement 
     : 
     ^('WHILE' e=expression head='DO' 
      { 
       int loopHead =((CommonTree) head).getTokenStartIndex(); 

      } 

      stat_seq 

      { 
       if ($e.result==1) { 
        input.seek(loopHead); 
        doWhileStatement(); 
       } 
      } 
     'ENDDO') 
; 

備案這裏有一些我寫的其他命令：（忽略寫在括號中的代碼 ，這是對的產生。在文本文件中的命令）

stat_seq 
      : 
      (statement)+ 
      ; 
statement 
     : 
     ^(':=' ID e=expression) { variables.put($ID.text,e); } 
     | ^('WRITE' expression) 
     { 
      ch.emitRM("LDC",ac,$expression.result,0,"pass the expression value to the ac reg"); 
      ch.emitRO("OUT",ac,0,0,"write out the value of ac"); 
     } 
     | ^('READ' ID) 
     { 
      ch.emitRO("IN",ac,0,0,"read value"); 
     } 
     | ^('IF' expression 'THEN' 
     { 
      ch.emitRM("LDC",ac1,$expression.result,0,"pass the expression result to the ac reg"); 
      int savedLoc1 = ch.emitSkip(1); 
     } 
     sseq1=stat_seq 
     'ELSE' 
     { 
      int savedLoc2 = ch.emitSkip(1); 
      ch.emitBackup(savedLoc1); 
      ch.emitRM("JEQ",ac1,savedLoc2+1,0,"skip as many places as needed depending on the expression"); 
      ch.emitRestore(); 
     } 
     sseq2=stat_seq 
     { 
      int savedLoc3 = ch.emitSkip(0); 
      ch.emitBackup(savedLoc2); 
      ch.emitRM("LDC",PC_REG,savedLoc3,0,"skip for the else command"); 
      ch.emitRestore(); 
     } 

      'ENDIF') 
     | doWhileStatement 
     ; 

任何幫助，將不勝感激，謝謝

Answer 1

我發現大家誰都有，我做到了這樣同樣的問題，它的工作：

^('WHILE' 

     {int c = input.index();} 
     expression 

     {int s=input.index();} 
     .*)// .* is a sequence of statements 

     { 
     int next = input.index(); // index of node following WHILE 
     input.seek(c); 
     match(input, Token.DOWN, null); 
     pushFollow(FOLLOW_expression_in_statement339); 
     int condition = expression(); 

     state._fsp--;    
     //there is a problem here 
     //expression() seemed to be reading from the grammar file and I couldn't 
     //get it to read from the tree walker rule somehow 
     //It printed something like no viable alt at input 'DOWN' 
     //I googled it and found this mistake 
     // So I copied the code from the normal while statement 
     // And pasted it here and it works like a charm 
     // Normally there should only be int condition = expression() 

     while (condition == 1) { 
      input.seek(s); 
      stat_seq();//stat_seq is a sequence of statements: (statement ';')+ 
      input.seek(c); 

      match(input, Token.DOWN, null); //Copied value from EvaluatorWalker.java 
      //cause couldn't find another way to do it 
      pushFollow(FOLLOW_expression_in_statement339); 
      condition = expression(); 

      state._fsp--; 
      System.out.println("condition:"+condition + " i:"+ variables.get("i")); 
     } 
     input.seek(next); 
    } 

我在我的代碼的註釋中寫了這個問題。如果任何人都可以幫助我，併爲我回答這個問題，我將不勝感激。這太奇怪了，幾乎沒有任何正確的方式在樹上的語法實現循環的反饋。

問候， 亞歷