OneWayList.java

package alice.tuprolog;

import java.util.List;
import java.util.NoSuchElementException;

class OneWayList<E> {
	
	private E head;
	private OneWayList<E> tail;
	
	public OneWayList(E head, OneWayList<E> tail) {
		this.head = head;
		this.tail = tail;
	}
	
	public static <T> OneWayList<T> transform(List<T> list) {
		if (list.isEmpty())
			return null;
		return new OneWayList<T>(list.remove(0), transform(list));
	}
	
	public E getHead() {
		return head;
	}
	
	public void setHead(E head) {
		this.head = head;
	}

	public OneWayList<E> getTail() {
		return tail;
	}
	
	public void setTail(OneWayList<E> tail) {
		this.tail = tail;
	}

	public void addLast(OneWayList<E> newTail) {
		if (tail == null) {
			tail = newTail;
			return;
		}
		tail.addLast(newTail);
	}
	
	public OneWayList<E> get(int index) {
		if (tail == null)
			throw new NoSuchElementException();
		if (index <= 0)
			return this;
		return tail.get(index - 1);
	}

	@Override
	public String toString() {
		String elem;
		if (head == null)
			elem = "null";
		else
			elem = head.toString();
		if (tail == null)
			return "[" + elem + "]";
		return "[" + tail.toString(elem) + "]";
	}
	
	private String toString(String elems) {
		String elem;
		if (head == null)
			elem = "null";
		else
			elem = head.toString();
		if (tail == null)
			return elems + "," + elem;
		return elems + "," + tail.toString(elem);
	}
	
}