kweimann

import random


class CodeMaker(object):
    def make_code(self):
        """
        code maker invents a secret code
        """
        raise NotImplemented()

richfitz

## Empty list -- just use the empty environment for this.
nil <- function() {
  emptyenv()
}

## Test if a list is the empty list:
is_empty <- function(lis) {
  identical(lis, nil())
}