//tabstop=4
//*****************************************************************************/
// Project: jpl
//
// File:    $Id$
// Date:    $Date$
// Author:  Fred Dushin <fadushin@syr.edu>
//          
//
// Description:
//    
//
// -------------------------------------------------------------------------
// Copyright (c) 1998 Fred Dushin
//                    All rights reserved.
// 
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Library Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
// 
// This library 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 Library Public License for more details.
// -------------------------------------------------------------------------
// $Id$
//*****************************************************************************/
package jpl;

import java.util.Hashtable;
import jpl.fli.*;

//----------------------------------------------------------------------/
// String
/**
 * A String is a Term with a java.lang.String value.  Use this 
 * class to represent Prolog strings.
 * <pre>
 * jpl.String s = new jpl.String( "Haddock's Eyes" );
 * </pre>
 * 
 * <hr><i>
 * Copyright (C) 1998  Fred Dushin<p>
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.<p>
 * 
 * This library 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 Library Public License for more details.<p>
 * </i><hr>
 * @author  Fred Dushin <fadushin@syr.edu>
 * @version $Revision$
 */
// Implementation notes:  
// 
//----------------------------------------------------------------------/
public class String
extends      Term
{
	//==================================================================/
	//  Attributes
	//==================================================================/

	/**
	 * the String's value
	 */
	java.lang.String value_ = null;
	
	/**
	 * @return the String's value
	 */
	public final java.lang.String
	value()
	{
		return value_;
	}
		
	//==================================================================/
	//  Contructors and Initialization
	//==================================================================/

	//------------------------------------------------------------------/
	// String
	/**
	 * A String holds a java.lang.String and represents a Prolog String,
	 * whose internal representation may vary across Prolog implementations.
	 * 
	 * @param   value  the java.lang.String value of this String.
	 */
	// Implementation notes:  
	// 
	//------------------------------------------------------------------/
	public
	String( java.lang.String value )
	{
		this.value_ = value;
	}

	//==================================================================/
	//  Converting Terms to term_ts
	//==================================================================/

	//------------------------------------------------------------------/
	// put
	/**
	 * To put an String in a term, we put the characters of the 
	 * String into the term_t.
	 * 
	 * @param   var_table  A Hashtable containing term_t's that are
	 * bound to (have packed in) Prolog variables as elements.  The
	 * Elements are keyed by jpl.Variable instances.  Cf. the put()
	 * implementation in the Variable class.
	 * @param   term  A (previously created) term_t which is to be
	 * packed with a Prolog term-type appropriate to the Term type
	 * (e.g., Atom, Variable, Compound, etc.) on which the method is
	 * invoked.)
	 */
	// Implementation notes: 
	// 
	//------------------------------------------------------------------/
	protected final void
	put( Hashtable var_table, term_t term )
	{
		Prolog.put_string_chars( term, value_ );
	}

	
	//==================================================================/
	//  Converting term_ts to Terms
	//==================================================================/
	
	//------------------------------------------------------------------/
	// from_term_t
	/**
	 * Converts a term_t to a String.  Assuming the term is an
	 * Prolog String, we just create a new String using the 
	 * characters in the Prolog String.
	 * 
	 * @param   term     The term_t to convert
	 * @return           A new String
	 */
	// Implementation notes:  
	// 
	//------------------------------------------------------------------/
	protected static Term
	from_term_t( Hashtable vars, term_t term )
	{
		StringHolder holder = new StringHolder();
		Prolog.get_string( term, holder );
		
		return new String( holder.value );
	}
	
	

	//==================================================================/
	//  Computing Substitutions
	//==================================================================/


	//------------------------------------------------------------------/
	// computeSubstitution
	/**
	 * Nothing needs to be done if the Term is an Atom.
	 * 
	 * @param   table  table holding Term substitutions, keyed on
	 *                 Variables.
	 */
	// Implementation notes:  
	// 
	//------------------------------------------------------------------/
	protected final void
	computeSubstitution( Hashtable bindings, Hashtable vars )
	{
	}


	//==================================================================/
	//  
	//==================================================================/

	
	public java.lang.String
	toString()
	{
		return value_;
	}
	
	public java.lang.String
	debugString()
	{
		return "(String " + toString() + ")";
	}

	
	//------------------------------------------------------------------/
	// equals
	/**
	 * Two Strings are equal if their values are equal
	 * 
	 * @param   obj  The Object to compare
	 * @return  true if the Object satisfies the above condition
	 */
	// Implementation notes:
	// 
	//------------------------------------------------------------------/
	public final boolean
	equals( Object obj )
	{
		if ( this == obj ){
			return true;
		}
		
		if ( ! (obj instanceof String) ){
			return false;
		}
		
		return value_.equals( ((String)obj).value_ );
	}}

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