package net.sf.saxon.expr;

import java.util.Iterator;
import java.util.NoSuchElementException;

/**
 * An iterator over a pair of objects (typically sub-expressions of an expression)
 */
public class PairIterator<T> implements Iterator<T> {

    private T one;
    private T two;
    private int pos = 0;

    /**
     * Create an iterator over two objects
     * @param one the first object to be returned
     * @param two the second object to be returned
     */

    public PairIterator(T one, T two) {
        this.one = one;
        this.two = two;
    }

    /**
     * Returns <tt>true</tt> if the iteration has more elements. (In other
     * words, returns <tt>true</tt> if <tt>next</tt> would return an element
     * rather than throwing an exception.)
     *
     * @return <tt>true</tt> if the iterator has more elements.
     */

    public boolean hasNext() {
        return pos<2;
    }

    /**
     * Returns the next element in the iteration.
     *
     * @return the next element in the iteration.
     * @exception NoSuchElementException iteration has no more elements.
     */
    public T next() {
        switch (pos++) {
            case 0: return one;
            case 1: return two;
            default: throw new NoSuchElementException();
        }
    }

    /**
     *
     * Removes from the underlying collection the last element returned by the
     * iterator (optional operation).  This method can be called only once per
     * call to <tt>next</tt>.  The behavior of an iterator is unspecified if
     * the underlying collection is modified while the iteration is in
     * progress in any way other than by calling this method.
     *
     * @exception UnsupportedOperationException if the <tt>remove</tt>
     *		  operation is not supported by this Iterator.

     * @exception IllegalStateException if the <tt>next</tt> method has not
     *		  yet been called, or the <tt>remove</tt> method has already
     *		  been called after the last call to the <tt>next</tt>
     *		  method.
     */
    public void remove() {
        throw new UnsupportedOperationException();
    }
}

//
// The contents of this file are subject to the Mozilla Public License Version 1.0 (the "License");
// you may not use this file except in compliance with the License. You may obtain a copy of the
// License at http://www.mozilla.org/MPL/
//
// Software distributed under the License is distributed on an "AS IS" basis,
// WITHOUT WARRANTY OF ANY KIND, either express or implied.
// See the License for the specific language governing rights and limitations under the License.
//
// The Original Code is: all this file
//
// The Initial Developer of the Original Code is Saxonica Limited.
// Portions created by ___ are Copyright (C) ___. All rights reserved.
//
// Contributor(s):
//