ex_03_4.py

#!/usr/bin/python
#AUTHOR: alexxa
#DATE: 24.12.2013
#SOURCE: Think Python: How to Think Like a Computer Scientist by Allen B. Downey
# http://www.greenteapress.com/thinkpython/html/index.html
#PURPOSE: Chapter 3. Functions

# Exercise 3.4
# A function object is a value you can assign to a variable or 
# pass as an argument. For  example, do_twice is a function that 
# takes a function object as an argument and calls it twice:
# def do_twice(f):
#     f()
#     f()
# Here is an example that uses do_twice to call a function named
# print_spam twice.
# def print_spam():
#     print 'spam'
# do_twice(print_spam)
# 1. Type this example into a script and test it.
# 2. Modify do_twice so that it takes two arguments, a function 
# object and a value, and calls the function twice, passing the 
# value as an argument.
# 3. Write a more general version of print_spam, called print_twice, 
# that takes a string as a parameter and prints it twice.
# 4. Use the modified version of do_twice to call print_twice twice, 
# passing 'spam' as an argument.
# 5. Define a new function called do_four that takes a function object 
# and a value and calls the function four times, passing the value as 
# a parameter. There should be only two statements in the body of this 
# function, not four.

arg = 'spam'
def do_twice(f, arg):
    f(arg)
    f(arg)

def print_twice(arg):
    print(arg)
    print(arg)

do_twice(print_twice, arg)
print()

def do_four(f, arg):
    do_twice(f, arg)
    do_twice(f, arg)

do_four(print_twice, arg)

#END