/**
 * A (real) Stack Interface.
 *
 * Differs from the Java class Stack because it really is a stack;
 * differs slightly from the Koffman/Wolfgang book implementation in
 * that push() here has void return type.
 *
 * David Liben-Nowell 
 * CS127 (Carleton College, Winter 2006)
 */

public interface RealStack<E> {

  /** 
   * Inserts an item into the stack.
   */
  void push(E item);

  /**
   * Returns the most recently inserted object still in the stack.
   * The stack itself is unchanged.  Throws an EmptyStackException if
   * the stack is empty.
   */
  E peek();

  /**
   * Removes the most recently inserted object still in the stack, and
   * returns it.  Throws an EmptyStackException if the stack is empty.
   */
  E pop();

  /** 
   * Returns true if and only if there are no elements left in the stack.
   */
  boolean empty();
}