package edu.vt.marian.search;

import java.util.*;
import java.io.*;

import edu.vt.marian.common.*;


/**
   The Weighted Object Set with no elements.
    <p> JDK Version  : 1.1.5
	@author	Priyamvadha Lakshminarayanan
	@author	Prajakta Joshi
	@see	WtdObjSet
*/

public class EmptyWtdObjSet implements WtdObjSet
{
	protected Debug debug;	// The inevitable.

	/**
   		The WtdObjSetEnumeration for Empty sets, where there is very
			little to enumerate ;-}.
	*/
	public class Enum implements WtdObjSetEnumeration
	{
		public Enum()
		{
		}

		/**
			Skip forward a certain number of elements.
			@param	k	How many elements to skip (if other than 0, this
					surely fails for the empty set!).
			@exception	NoSuchElementException
			*/
		public void skip(int k) throws NoSuchElementException
		{
			if (k != 0)
				throw(new NoSuchElementException());
		}

		public Object nextElement() throws NoSuchElementException
		{
			throw(new NoSuchElementException());
		}


		public boolean hasMoreElements()
		{
			return( false );
		}

		public int sample(int num, WtdObjBag sampleBag)
		{
			return( ReturnCodes.OK );
		}

		public int sampleToWt(Weight minWt, WtdObjBag sampleBag)
		{
	 		return( ReturnCodes.OK );
		}


		public int exactNumRemaining()
		{
			return( 0 );
		}

		public int approxNumRemaining()
		{
			return( 0 );
		}

		public int maxNumRemaining()
		{
			return( 0 );
		}

	} //End of (EmptyWtdObjSet) Enum


	public EmptyWtdObjSet(Debug d)
	{
		debug = d;
	}

	/**
		Create an Enumeration -- actually a WtdObjSetEnumeration -- 
			for this set.
	*/
	public WtdObjSetEnumeration elements()
	{
		return( new Enum() );
	}


	/**
		Is this set empty?
		@return	true / false
	*/
	public boolean isEmpty()
	{
		return( true );
	}


	/**
		Is a given ID an element of this set?	
		@param	id	The (ID of the) element to be tested.
		@return	null -- the element is not in the set.
		<BR>	any valid Weight -- the element is in the set with that Weight.
	*/
	public Weight isElt(FullID id)
	{
		return( null );
	}


	/**
		Return the exact number of elements in this set (may be costly).
	*/
	public int exactSize()
	{
		return(0);
	}

	/**
		Return the approximate number of elements in this set (can be cheap
			and dirty).
	*/
	public int approxSize()
	{
		return(0);
	}

	/**
		Return the maximum number of elements in this set (can be cheap
			and dirty).
	*/
	public int maxSize()
	{
		return(0);
	}

	/**
		Return a human-readable string for this entire set (may be large).
	*/
	public String toString()
	{
		return( new String("{}") );
	}

	/**
		Return a short human-readable string that quickly describes this set.
	*/
	public String profile()
	{
		return( new String("{}") );
	}
} //End of class