/** A list of IntLists. */
public class IntList2 {
    /** A List with head and tail. */
    public IntList2 (IntList head, IntList2 tail) {
        this.head = head; this.tail = tail;
    }

    /** A List with null head and tail. */
    public IntList2 () { this (null, null); }

    public IntList head;
    public IntList2 tail;

    /** A new IntList2 containing the ints in ARGS. */
    public static IntList2 list (IntList ... args) {
        IntList2 sentinel = new IntList2 (null, null);

        IntList2 p;
        p = sentinel;
        for (IntList x : args)
            p = p.tail = new IntList2 (x, null);
        return sentinel.tail;
    }

    /** A new IntList2 containing the lists of ints corresponding
     *  to the arrays in A. */
    public static IntList2 list (int[][] A) {
        IntList2 sentinel = new IntList2 (null, null);

        IntList2 p;
        p = sentinel;
        for (int[] x : A)
            p = p.tail = new IntList2 (IntList.list (x), null);
        return sentinel.tail;
    }

    /** True iff X is an IntList2 or int[][] containing the same sequence of ints
     *  as THIS. */
    public boolean equals (Object x) {
        if (x instanceof IntList2) {
            IntList2 L = (IntList2) x;
            IntList2 p;
            for (p = this; p != null && L != null; p = p.tail, L = L.tail) {
                if ((p.head == null && L.head != null)
                    || (p.head != null && ! p.head.equals (L.head)))
                    return false;
            }
            if (p == null && L == null)
                return true;
        } else if (x instanceof int[][]) {
            int[][] A = (int[][]) x;
            IntList2 p;
            int i;
            for (i = 0, p = this; i < A.length && p != null; 
                 i += 1, p = p.tail) {
                if ((p.head == null && A[i].length != 0)
                    || ! p.head.equals (A[i]))
                    return false;
            }
            if (i == A.length && p == null)
                return true;
        }
        return false;
    }

    /** Convert THIS into a readable String. */
    public String toString () {
        StringBuffer b = new StringBuffer ();
        b.append ("[");
        for (IntList2 L = this; L != null; L = L.tail) 
            b.append (" " + L.head); 
        b.append ("]");
        return b.toString ();
    }


}