/*
 * ListPlus.java
 *
 * Created on March 28, 2007, 5:52 AM
 *
 * To change this template, choose Tools | Template Manager
 * and open the template in the editor.
 */
package exercise5;

/**
 *
 * @author Sui Huang
 */
import java.util.*;
public class ListPlus extends List{
    
    /** Creates a new instance of ListPlus */
    private ListPlus() {
        // dummy
    }
    
    public static boolean isEmpty(List k) {
        return k.same(List.nil());
    }
    
    public static Element getHead(List k) throws BadIndexException {
        return k.getMember(0);
    }
    
    public static List getTail(List k) throws BadIndexException{
        return List.drop(1,k);
    }
    
    public static int getLength(List k) {
        int length=0;
        List L=k;
        while (true){
            try {
                L = List.drop(1,L);
                length = length+1;
            } catch (BadIndexException e){
                break;
            }
        }
        return length;
    }
    
    public static int getHeight(List k) {
        int length = getLength(k);
        // this is an extramely unbalanced tree
        if (length==0){
            return 0;
        } else if (length==1){
            return 1;
        } else {
            return (length-1);
        }
    }
    
    public static List reverse(List k) {
        List L=List.nil();
        int len = getLength(k);
        for (int i=0; i<len; i++) {
            try {
                L = List.cons(k.getMember(i),L);
            } catch (Exception e){
                System.out.println(e.toString());
            }
        }
        return L;
    }
    
}