//<PLAINTEXT>
package Trees;

/**
 * ExpressionTree.java
 *
 *
 * Created: Tue Apr  1 14:23:47 2003
 *
 * @author <a href="mailto:shapiro@cse.buffalo.edu">Stuart C. Shapiro</a>
 */

public class ExpressionTree extends BinaryTree {

    /**
     * Creates a new empty <code>ExpressionTree</code> instance.
     *
     */
    public ExpressionTree (){
	super();
    }

    /**
     * Creates a new <code>ExpressionTree</code> instance.
     *
     * @param value contents of this node of this tree.
     * @param lt the left sub-<code>BinaryTree</code> of this tree.
     * @param rt the right sub-<code>BinaryTree</code> of this tree.
     */
    public ExpressionTree (Object value, ExpressionTree lt, ExpressionTree rt) {
	super(value, lt, rt);
    }

    public static ExpressionTree operand(Object v) {
	ExpressionTree opnd = new ExpressionTree();
	opnd.setContents(v);
	return opnd;
    }

    public String preorderToString() {
	if (isEmpty()) return "";
	if (isLeaf()) return "" + getContents() + " ";
	return "" + getContents() + " "
	    + ((ExpressionTree)getLeft()).preorderToString()
	    + ((ExpressionTree)getRight()).preorderToString();
    }

    public String inorderToString() {
	if (isEmpty()) return "";
	if (isLeaf()) return "" + getContents();
	return "(" + ((ExpressionTree)getLeft()).inorderToString()
	    + " " + getContents() + " "
	    + ((ExpressionTree)getRight()).inorderToString() + ")";
    }

    public String postorderToString() {
	if (isEmpty()) return "";
	if (isLeaf()) return "" + getContents() + " ";
	return ((ExpressionTree)getLeft()).postorderToString()
	    + ((ExpressionTree)getRight()).postorderToString()
	    +  " " + getContents() + " ";
    }

    public static void main (String[] args) {
	// ((5 * (10 - 4)) / (18 / (2 * 3)))
	ExpressionTree expr =
	    new ExpressionTree("/",
			       new ExpressionTree("*",
						  operand("5"),
						  new ExpressionTree("-",
								     operand("10"),
								     operand("4"))),
			       new ExpressionTree("/",
						  operand("18"),
						  new ExpressionTree("*",
								     operand("2"),
								     operand("3"))));
	System.out.println("As binary tree: " + expr);
	System.out.println("Inorder: " + expr.inorderToString());
	System.out.println("Preorder: " + expr.preorderToString());
	System.out.println("Postorder: " + expr.postorderToString());
    } // end of main ()
    
    
}// ExpressionTree