CS143-Lab/assignments/PA4J/ListNode.java

/*
Copyright (c) 2000 The Regents of the University of California.
All rights reserved.

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AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
ON AN "AS IS" BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATION TO
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*/

import java.io.PrintStream;
import java.util.Vector;
import java.util.Enumeration;

/** Base class for lists of AST elements.

    <p> 

    (See <a href="TreeNode.html">TreeNode</a> for a discussion of AST
    nodes in general)

    <p>

    List phyla have a distinct set of operations for constructing and
    accessing lists.  For each phylum named <em>X</em> there is a phylum
    called <em>X</em>s (except for <code>Classes</code>, which is a list
    of <code>Class_</code> nodes) of type <code>List[X]</code>.

    <p> 

    An empty list is created with <code>new Xs(lineno)</code>.  Elements
    may be appended to the list using either <code>addElement()</code>
    or <code>appendElement()</code>.  <code>appendElement</code> returns
    the list itself, so calls to it may be chained, as in <code>
    list.appendElement(Foo).appendElement(Bar).appendElement(Baz)</code>.

    <p>
    
    You can use <code>java.util.Enumeration</code> to iterate through
    lists.  If you are not familiar with that interface, look it up in
    the Java API documentation.  Here's an example of iterating through
    a list:

<pre>
  for (Enumeration e = list.getElements(); e.hasMoreElements(); ) {
    Object n = e.nextElement();
    ... do something with n ...
  }
</pre>

    Alternatively, it is possible to iterate using an integer index:

<pre>
  for (int i = 0; i < list.getLength(); i++) {
    ... do something with list.getNth(i) ...
  }
</pre>

    Note: <code>nextElement()</code> returns the value of type
    <code>Object</code> and <code>getNth()</code> returns the value of
    type <code>TreeNode</code>.  You will most likely need to cast it to
    the type appropriate for the list element. <em>This is one of the
    very few cases where casting is actually necessary and
    appropriate</em>.

*/
    
abstract class ListNode extends TreeNode {
    private Vector elements;

    protected ListNode(int lineNumber, Vector elements) {
	super(lineNumber);
	this.elements = elements;
    }

    /** Builds a new list node
     *
     * @param lineNumber line in the source file from which this node came. 
     * */
    protected ListNode(int lineNumber) {
	super(lineNumber);
	elements = new Vector();
    }

    /** Creates a deep copy of this list.
     *
     * None of the elements are shared between the lists, e.g. all
     * elements are duplicated (which is what "deep copy" means).
     *
     * @return a copy of this elements vector
     * */
    protected Vector copyElements() {
	Vector cp = new Vector();
	for (int i = 0; i < elements.size(); i++) {
	    cp.addElement(((TreeNode)elements.elementAt(i)).copy());
	}
	return cp;
    }

    /** Returns the class of list elements.
     *
     * @return the element class
     * */
    public abstract Class getElementClass();

    /** Retreives nth element of the list.
     *
     * @param n the index of the element
     * @return the element
     * */
    public TreeNode getNth(int n) {
	return (TreeNode)elements.elementAt(n);
    }

    /** Retreives the length of the list.
     *
     * @return the length of the list
     * */
    public int getLength() {
	return elements.size();
    }

    /** Retreives the elements of the list as Enumeration.
     *
     * @return the elements
     * */
    public Enumeration getElements() {
	return elements.elements();
    }

    /** Appends an element to the list.
     * 
     * <p>Note: each generated subclass of ListNode also has an
     * appendElement() method, which calls addElement() and returns the
     * list of the appropriate type, so that it can be used like this:
     * <code>l.appendElement(i).appendElement(j).appendElement(k);</code>
     *
     * @param node a node to append
     * */
    public void addElement(TreeNode node) {
	elements.addElement(node);
    }

    /** Pretty-prints this list to this output stream.
     *
     * @param out the output stream
     * @param n the number of spaces to indent the output
     * */
    public void dump(PrintStream out, int n) {
	out.print(Utilities.pad(n));
	out.print("list\n");
	for (int i = 0; i < getLength(); i++) {
	    getNth(i).dump(out, n + 2);
	}
	out.print(Utilities.pad(n));
	out.print("(end_of_list)\n");
    }

    /** Returns a string representation of this list.
     *
     * @return a string representation
     * */
    public String toString() {
	return elements.toString();
    }
}