/*  SCCS - @(#)YYtoken_Stack.java	1.2 - 02/28/99 - 12:39:32 */

package pp.src.jbf;

/*
 * @(#)Stack.java	1.12 95/08/11  
 *
 * Copyright (c) 1994 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Permission to use, copy, modify, and distribute this software
 * and its documentation for NON-COMMERCIAL purposes and without
 * fee is hereby granted provided that this copyright notice
 * appears in all copies. Please refer to the file "copyright.html"
 * for further important copyright and licensing information.
 *
 * SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF
 * THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
 * TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR
 * ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR
 * DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES.
 */

import java.util.*;

/**
 * A Last-In-First-Out(LIFO) stack of ints.
 *
 * @version 	1.12, 08/11/95
 * @author 	Jonathan Payne
 */
public
class YYtoken_Stack extends Vector {
    /**
     * Pushes an item onto the stack.
     * @param item the item to be pushed on.
     */
    public YYtoken push(YYtoken item) {
	addElement(item);
	return item;
    }

    /**
     * Pops an item off the stack.
     * @exception EmptyStackException If the stack is empty.
     */
    public YYtoken pop() throws EmptyStackException {
	YYtoken	obj;
	int	len = size();

	obj = peek();
	removeElementAt(len - 1);
	return obj;
    }

    /**
     * Peeks at the top of the stack.
     * @exception EmptyStackException If the stack is empty.
     */
    public YYtoken peek() throws EmptyStackException {
	int	len = size();

	if (len == 0)
	    throw new EmptyStackException();
	return (YYtoken)elementAt(len - 1);
    }

    public boolean empty() {
	return size() == 0;
    }

    /**
     * Sees if an int is on the stack.
     * @param o the desired int
     * @return the distance from the top, or -1 if it is not found.
     */
    public int search(YYtoken o) {
	int i = lastIndexOf(o);

	if (i >= 0) {
	    return size() - i;
	}
	return -1;
    }

/**************************************************/
    public void clear() {
	setSize(0);
    }

    public void popn(int n) throws EmptyStackException {
	int len = size();
	if(n < 0 || n > len) {
	    throw new EmptyStackException();
	}
	setSize(len - n);
    }

    public YYtoken ith(int i) throws EmptyStackException {
	int len = size();
	if(i < 0 || i >= len)
	    throw new EmptyStackException();
	return (YYtoken)elementAt(i);

    }

    public int depth() {
	return size();
    }

    public YYtoken tth(int i) throws EmptyStackException {
	int len = size();
	i = - i;
	if(i < 0 || i >= len)
	    throw new EmptyStackException();
	return (YYtoken)elementAt(len  - (i+1));

    }

}