We help IT Professionals succeed at work.

Check out our new AWS podcast with Certified Expert, Phil Phillips! Listen to "How to Execute a Seamless AWS Migration" on EE or on your favorite podcast platform. Listen Now

x

Writing a Compiler HELP~

jtcy
jtcy asked
on
Medium Priority
256 Views
Last Modified: 2013-11-23
Hi all, I am writing a compiler for a language called RCL, but stuck at the parser stage. Apparently, I have done the lexer, but now needs to do the parser. We are told to write a parser class, containing sub-parsers methods for each productions. And each sub parsers should also instantiate an AST node unique to that production. I am having problem of linking the lexer and the parser. i am stuck. here;s my lexer (its first part):

************************************************************************************
//First part of the descrition file: Contains codes to be added to the top of symbols.lex.java
import java.io.*;
import java.lang.System;
import compiler.sym;  // In here, all the definitions of token values
import ast.*;


class Compiler
  {
    /*
     * Just a simple driver - loops till end-of-file **
     * prints out the yytoken received..via the to_string method in yytoken
     *
     * **NOTE: Eof weirdness - For some strange reason (as yet unresolved)
     * it takes 3 (three) ^D's to make EOF happen.  Don't know why.
     *
     */
    static Yytoken current_symbol;
    static Yylex scanner;
   
    public static void main(String[] args) throws java.io.IOException
     {
            FileReader inFile = new FileReader(args[0]);
            scanner = new Yylex(inFile);
          
           do
            {
            
              System.out.println(current_symbol);
            }
            while (current_symbol.m_index != sym.EOF);
     }
     
     public Yytoken next_symbol() throws java.io.IOException
      {
          current_symbol = scanner.yylex();
          return current_symbol;
      }
      
      
      public boolean have(int s) throws java.io.IOException
      {
            if (current_symbol.m_index == s)
             {
                   next_symbol();
                   return (true);
             }
            else
                  return(false);
                  
      }

    public void mustbe(int s) throws java.io.IOException
    {
          if (current_symbol.m_index == s)
          {
                next_symbol();
          }
          else
          {
                System.out.println("error");
          }
    }
   
   
   
   
 }
 

 
class Utility
  {
    public static void my_assert(boolean expr)
      {
             if (false == expr)
               {
                  throw (new Error("Error: Assertion failed."));
               }
      }
    private static final String errorMsg[] =
     {
        "Error: Unmatched end-of-comment punctuation.",
        "Error: Unmatched start-of-comment punctuation.",
        "Error: Unclosed string.",
        "Error: Illegal character."
     };
    public static final int E_ENDCOMMENT = 0;
    public static final int E_STARTCOMMENT = 1;
    public static final int E_UNCLOSEDSTR = 2;
    public static final int E_UNMATCHED = 3;
    public static void error(int code)
      {
             System.out.println(errorMsg[code]);
      }
  }

class Yytoken
 {
   Yytoken (int index,String text,int line,int charBegin,int charEnd,String t_type)
      {
           m_index = index;
          m_text = new String(text);
          m_line = line;
          m_charBegin = charBegin;
          m_charEnd = charEnd;
          m_type = t_type;
      }
   public int m_index;
   public String m_text;
   public int m_line;
   public int m_charBegin;
   public int m_charEnd;
   public String m_type;
   public String toString()
    {
      return m_line +","+m_charBegin+":"+m_charEnd+"#"+m_type+"#"+m_text+"#";
    }
 }
 
******************************************************************************************

And here is my parser: i have only build an ifstatement production. just for testing.


import ast.*;
import compiler.sym;


public class Parser
{
   
   public Parser()
    {
          
    }

   
    public static ASTNode nIfStatement()
      {
            IfStatementNode thisOne = new IfStatementNode();
            mustbe(sym.tIF);
            thisOne.addchild(nRvalue());
            mustbe(sym.tTHEN);
            thisOne.addchild(nStatementList());
            while (have(sym.tELSEIF))
             {
                  thisOne.addchild(nRvalue());
                  mustbe(sym.tTHEN);
                  thisOne.addchild(nStatementList());
             };
            if (have(sym.tELSE))
             {
                   thisOne.addchild(nStatementList());
             }
            mustbe(sym.tENDIF);
            return thisOne;
      };
 
  }
  **************************************************************************************
 
 Okay, what i am not sure is where to put the mustbe() and have() method. I am confused on whether to implement like above, putting them in the lexer file or put in the parser file. Like now, the compiler would complain it cant find the mustbe method and have method.

Help~
 
 
 
 
 
 
 
 
 
 
 
Comment
Watch Question

Mayank SPrincipal Technologist
CERTIFIED EXPERT

Commented:

Author

Commented:
um..have added the classpath. but i just heard from friend that theres no need to change the classpath. but using packaging. : (
Mayank SPrincipal Technologist
CERTIFIED EXPERT

Commented:
Well, can you post a comment on it so that we can carry the discussion on that page. Please tell the specific problem now.
Commented:
Unlock this solution with a free trial preview.
(No credit card required)
Get Preview
Unlock the solution to this question.
Thanks for using Experts Exchange.

Please provide your email to receive a free trial preview!

*This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

OR

Please enter a first name

Please enter a last name

8+ characters (letters, numbers, and a symbol)

By clicking, you agree to the Terms of Use and Privacy Policy.