# Rlist class defined for CS61A at UC Berkeley
# Edited by Mark Miyashita
# http://markmiyashita.com/cs61a

class Rlist(object):
    """A recursive list consisting of a first element and the rest.

    >>> s = Rlist(1, Rlist(2, Rlist(3)))
    >>> len(s)
    3
    >>> s[0]
    1
    >>> s[1]
    2
    >>> s[2]
    3
    """
    class EmptyList(object):
        def __len__(self):
            return 0

    empty = EmptyList()

    def __init__(self, first, rest=empty):
        self.first = first
        self.rest = rest

    def __repr__(self):
        f = repr(self.first)
        if self.rest is Rlist.empty:
            return 'Rlist({0})'.format(f)
        else:
            return 'Rlist({0}, {1})'.format(f, repr(self.rest))

    def __len__(self):
        return 1 + len(self.rest)

    def __getitem__(self, i):
        if i == 0:
            return self.first
        return self.rest[i - 1]