"""This module contains code from

Think Python by Allen B. Downey

http://thinkpython.com

Copyright 2012 Allen B. Downey

License: GNU GPLv3 http://www.gnu.org/licenses/gpl.html

"""

def do_twice(f, arg):

f(arg)

f(arg)

def print_twice(arg):

print arg

print arg

do_twice(print_twice, 'spam')

print ''

def do_four(f, arg):

do_twice(f, arg)

do_twice(f, arg)

do_four(print_twice, 'spam')

print ''