/* Tree.java */

package tree;

/**
 * An interface for general trees (i.e., where a node can have any number of
 * children).
 * @author Jonathan Shewchuk
 */

public interface Tree {

  public boolean isEmpty();
  /**
   * isEmpty() returns true if the Tree has no nodes; false otherwise.
   */

  public int size();
  /**
   * size() returns the number of nodes in the Tree.
   */

  public TreePosition root();
  /**
   * root() constructs a TreePosition that refers to the root node.  Returns
   * an invalid position if the tree is empty.
   */

  public void insertRoot(Object value);
  /**
   * insertRoot() inserts a node containing "value" at the root of the tree.
   * If a root already exists, it becomes a child of the node containing
   * "value".
   */

}