ubc.cs.JLog.Builtins.Goals.jReadGoal Maven / Gradle / Ivy

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/*
    This file is part of JLog.

    Created by Glendon Holst for Alan Mackworth and the 
    "Computational Intelligence: A Logical Approach" text.
    
    Copyright 1998, 2000, 2002 by University of British Columbia and 
    Alan Mackworth.
    
    This notice must remain in all files which belong to, or are derived 
    from JLog.
    
    Check  or 
     for further information
    about JLog, or to contact the authors.
     
    JLog is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    JLog is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with JLog; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
    URLs:  or 
*/
//#########################################################################
//	ReadGoal
//#########################################################################
 
package ubc.cs.JLog.Builtins.Goals;

import java.lang.*;
import java.util.*;
import java.io.*;
import ubc.cs.JLog.Terms.*;
import ubc.cs.JLog.Foundation.*;
import ubc.cs.JLog.Parser.*;
import ubc.cs.JLog.Builtins.*;

/**
 * Goal for inputing text from the console.
 *
 * @author       Glendon Holst
 * @version      %I%, %G%
 */
public class jReadGoal extends jGoal
{
 protected jRead 			read;
 
 // for use by read
 public jTerm 				term;
 public jUnifiedVector 		unified;
 
 public 	jReadGoal(jRead r,jTerm t)
 {
  read = r;
  term = t;
  unified = new jUnifiedVector();
 };
 
 public boolean 	prove(iGoalStack goals,iGoalStack proved)
 {jTerm 		in;
 
  in = getInput();
  
  if (read.prove(this,in))
  {
   proved.push(this);
   return true;
  }
  else
  {
   { // we need to initialize goal to potentially restart
    unified.restoreVariables();
   }
   goals.push(this); // a retry that follows may need a node to remove or retry
   return false;
  }
 };

 public boolean 	retry(iGoalStack goals,iGoalStack proved)
 {
  unified.restoreVariables();
  
  goals.push(this); // a retry that follows may need a node to remove or retry
  return false;
 }; 
 
 public void 	internal_restore(iGoalStack goals)
 {
  unified.restoreVariables();
 };
  
 protected jTerm  	getInput()
 {Thread 		thread = Thread.currentThread();
  
  if (thread instanceof jPrologServiceThread)
  {jPrologServiceThread		pst = (jPrologServiceThread) thread;
   jPrologServices			prolog = pst.getPrologServices();
   BufferedReader			in = prolog.getInput();
   PrintWriter				out = prolog.getOutput();
   String					input = null;
   
   if (in == null)
    throw new MissingInputServicesException("InputStream Services unavailable");

   while (input == null)
   {
    try
    {  	
     input = in.readLine();
    }
    catch (IOException e)
    {
     throw new InvalidInputException();
    }
   
    if (input == null)
     throw new InvalidInputException();   
   
    {pParseStream 	parser;
   
     parser = new pParseStream(input,prolog.getKnowledgeBase(),
                             prolog.getPredicateRegistry(),
                             prolog.getOperatorRegistry());
   
     try
     {jTerm 		trm;
    
      trm = parser.parseTerm(); 
    
      if (trm != null)
      {
       out.println(trm.toString(true));
       out.flush();
       return trm;    
      }
      else
       throw new InvalidInputException();   
     }
     catch (SyntaxErrorException e)
     {
	  out.println(input);
      out.println("SYNTAX ERROR:");
      out.println(e.toString());
	  out.flush();
	  input = null;
      out.println("Try Again...\n");
	  out.flush();	  
     }
     catch (TokenizeStreamException e)
     {
	  out.println(input);
      out.println("INTERNAL ERROR:");
      out.println(e.toString());
	  out.flush();
	  input = null;
      out.println("Try Again...\n");
	  out.flush();	  
     }
    }
   }
   throw new InvalidInputException();
  } 
  else
   throw new MissingInputServicesException();
 };
 
 public String 		getName() 
 {
  return read.getName();
 };
 
 public int 		getArity() 
 {
  return read.getArity();
 };
 
 public String 		toString()
 {StringBuffer 	sb = new StringBuffer();
   
  sb.append(getName()+"/"+String.valueOf(getArity())+" goal: ");
  sb.append(getName()+"("+term.toString()+")");
  
  return sb.toString();
 };
};