/**
 * An IntList is a list of ints.
 */
public class IntList {
  private ConsCell start; // first in the list or null

  /**
   * Construct a new IntList given its first ConsCell.
   * @param s the first ConsCell in the list or null
   */
   private IntList(ConsCell s) {
    start = s;
  }

    public static IntList make(int... values){
        IntList l = NIL;
        for(int i = values.length - 1; i >= 0; i--){
            l = l.cons(values[i]);
        }
        return l;
    }

    public final static IntList NIL = new IntList(null);

  /**
   * Cons the given element h onto us and return the
   * resulting IntList.
   * @param h the head int for the new list
   * @return the IntList with head h and us for a tail
   */
  public IntList cons (int h) {
    return new IntList(new ConsCell(h,start));
  }

  /**
   * Get our length.
   * @return our int length
   */
  public int length() {
    int len = 0;
    ConsCell cell = start;
    while (cell != null) { // while not at end of list
      len++;
      cell = cell.getTail();
    }
    return len;
  }

  /**
   * Print ourself to System.out.
   */
  public void print() {
    System.out.print("[");
    ConsCell a = start;
    while (a != null) {
      System.out.print(a.getHead());
      a = a.getTail();
      if (a != null) System.out.print(",");
    }
    System.out.println("]");
  }

  /**
   * A ConsCell is an element in a linked list of
   * ints.
   */
  private static class ConsCell {
    private int head; // the first item in the list
    private ConsCell tail; // rest of the list or null

    /** 
     * Construct a new ConsCell given its head and tail.
     * @param h the int contents of this cell
     * @param t the next ConsCell in the list or null
     */
    public ConsCell(int h, ConsCell t) {
      head = h;
      tail = t;
    }
    /**
     * Accessor for the head of this ConsCell.
     * @return the int contents of this cell
     */
    public int getHead() {
      return head;
    }

    /**
     * Accessor for the tail of this ConsCell.
     * @return the next ConsCell in the list or null
     */
    public ConsCell getTail() {
      return tail;
    }
  }
    
}