content: /* 
   * Kodkod -- Copyright (c) 2005-present, Emina Torlak
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy
   * of this software and associated documentation files (the "Software"), to deal
   * in the Software without restriction, including without limitation the rights
   * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   * copies of the Software, and to permit persons to whom the Software is
   * furnished to do so, subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in
   * all copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
   * THE SOFTWARE.
   */
  package kodkod.util.ints;
  
  /**
   * An entry in a {@link SparseSequence sparse sequence}.
   * 
   * @specfield index: int
   * @specfield value: E
   * 
   * @author Emina Torlak
   */
  public interface IndexedEntry<E> {
  	
  	/**
  	 * Returns the index of this entry.
  	 * @return this.index
  	 */
  	public abstract int index();
  	
  	/**
  	 * Returns the value stored in this entry.
  	 * @return this.value
  	 */
  	public abstract E value();
  	
  	/**
  	 * Compares the specified object with this entry for equality. Returns true if
  	 * the given object is also an indexed entry and the two entries 
  	 * have the same indeces and values. More formally, two entries e1 and e2 
  	 * are equal if e1.index = e2.index && e1.value = e2.value.  This ensures 
  	 * that the equals method works properly across different implementations of 
  	 * the IndexedEntry interface.
  	 * @return o in IndexedEntry && o.index = this.index && o.value = this.value
  	 */
  	public abstract boolean equals(Object o);
  	
  	/**
  	 * Returns the hash code value for this indexed entry. The hash code of an 
  	 * indexed entry e is defined to be:
  	 * e.index ^ (e.value=null ? 0 : e.value.hashCode()).
  	 * This ensures that e1.equals(e2) implies that e1.hashCode()==e2.hashCode() 
  	 * for any two IndexedEntries e1 and e2, as required by the general contract of 
  	 * Object.hashCode.
  	 */
  	public abstract int hashCode();
  }
  