CMU 15-112 Spring 2018: Fundamentals of Programming and Computer Science
Colab 9 (Due Thursday 22-Mar, at 10pm)

• This assignment is collaborative. That means you may work with other students enrolled in the course, and you may even help each other write code and debug. However, you must still type all of your own work, and you must fully understand the code that you submit. Even though this is collaborative, you may not directly copy any code from anyone, and you may not electronically share your code with anyone. See the syllabus for more details.
• List your collaboration partners (name and andrew id) in a comment on the first line of this file. If you collaborate with another student and do not include their name in a comment, it will be considered cheating. You may work alone if you want to, but we recommend working with others, as it generally leads to better learning.
• Be a good collaborator! Help everyone in your group, and accept their help if you need it. Don't be in a hurry to finish the problems. Instead, take your time and be sure that everyone in the group is following and understanding. The goal is to learn, not just to finish.
• If you're looking for more people to collaborate with, you can request to be paired up with other 112 students using this form.

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• To start:
  1. Go to your folder named 'week9'
  2. Create a file named colab9.py.
  3. Edit colab9.py using Pyzo
  4. When you are ready, submit colab9.py to Autolab. You may submit up to 5 times.
• Do not hardcode the test cases in your solutions.

1. Book Class [40 pts]
   Write the Book class so that it passes testBookClass, and uses the OOP constructs we learned this week as appropriate.
   def testBookClass(): print("Testing Book class...", end="") # A Book has a title, and author, and a number of pages. # It also has a current page, which always starts at 1. There is no page 0! book1 = Book("Harry Potter and the Sorcerer's Stone", "J. K. Rowling", 309) assert(str(book1) == "Book<Harry Potter and the Sorcerer's Stone by " + "J. K. Rowling: 309 pages, currently on page 1>") book2 = Book("Carnegie Mellon Motto", "Andrew Carnegie", 1) assert(str(book2) == "Book<Carnegie Mellon Motto by Andrew Carnegie: " + "1 page, currently on page 1>") # You can turn pages in a book. Turning a positive number of pages moves # forward; turning a negative number moves backwards. You can't move past # the first page going backwards or the last page going forwards book1.turnPage(4) # turning pages does not return assert(book1.getCurrentPage() == 5) book1.turnPage(-1) assert(book1.getCurrentPage() == 4) book1.turnPage(400) assert(book1.getCurrentPage() == 309) assert(str(book1) == "Book<Harry Potter and the Sorcerer's Stone by " + "J. K. Rowling: 309 pages, currently on page 309>") book2.turnPage(-1) assert(book2.getCurrentPage() == 1) book2.turnPage(1) assert(book2.getCurrentPage() == 1) # You can also put a bookmark on the current page. This lets you turn # back to it easily. The book starts out without a bookmark. book3 = Book("The Name of the Wind", "Patrick Rothfuss", 662) assert(str(book3) == "Book<The Name of the Wind by Patrick Rothfuss: " + \ "662 pages, currently on page 1>") assert(book3.getBookmarkedPage() == None) book3.turnPage(9) book3.placeBookmark() # does not return assert(book3.getBookmarkedPage() == 10) book3.turnPage(7) assert(book3.getBookmarkedPage() == 10) assert(book3.getCurrentPage() == 17) assert(str(book3) == "Book<The Name of the Wind by Patrick Rothfuss: " + \ "662 pages, currently on page 17, page 10 bookmarked>") book3.turnToBookmark() assert(book3.getCurrentPage() == 10) book3.removeBookmark() assert(book3.getBookmarkedPage() == None) book3.turnPage(25) assert(book3.getCurrentPage() == 35) book3.turnToBookmark() # if there's no bookmark, don't turn to a page assert(book3.getCurrentPage() == 35) assert(str(book3) == "Book<The Name of the Wind by Patrick Rothfuss: " + \ "662 pages, currently on page 35>") # Finally, you should be able to compare two books directly and hash books book5 = Book("A Game of Thrones", "George R.R. Martin", 807) book6 = Book("A Game of Thrones", "George R.R. Martin", 807) book7 = Book("A Natural History of Dragons", "Marie Brennan", 334) book8 = Book("A Game of Spoofs", "George R.R. Martin", 807) assert(book5 == book6) assert(book5 != book7) assert(book5 != book8) s = set() assert(book5 not in s) s.add(book5) assert(book6 in s) assert(book7 not in s) s.remove(book6) assert(book5 not in s) book5.turnPage(1) assert(book5 != book6) book5.turnPage(-1) assert(book5 == book6) book6.placeBookmark() assert(book5 != book6) print("Done!")


2. Bird Class and Subclasses [35 pts]
   Write the Bird, Penguin, and MessengerBird classes so that they pass testBirdClasses and use the OOP constructs we learned this week as appropriate.
   def getLocalMethods(clss): import types # This is a helper function for the test function below. # It returns a sorted list of the names of the methods # defined in a class. It's okay if you don't fully understand it! result = [ ] for var in clss.__dict__: val = clss.__dict__[var] if (isinstance(val, types.FunctionType)): result.append(var) return sorted(result) def testBirdClasses(): print("Testing Bird classes...", end="") # A basic Bird has a species name, can fly, and can lay eggs bird1 = Bird("Parrot") assert(type(bird1) == Bird) assert(isinstance(bird1, Bird)) assert(bird1.fly() == "I can fly!") assert(bird1.countEggs() == 0) assert(str(bird1) == "Parrot has 0 eggs") bird1.layEgg() assert(bird1.countEggs() == 1) assert(str(bird1) == "Parrot has 1 egg") bird1.layEgg() assert(bird1.countEggs() == 2) assert(str(bird1) == "Parrot has 2 eggs") assert(getLocalMethods(Bird) == ['__init__', '__repr__', 'countEggs', 'fly', 'layEgg']) # A Penguin is a Bird that cannot fly, but can swim bird2 = Penguin("Emperor Penguin") assert(type(bird2) == Penguin) assert(isinstance(bird2, Penguin)) assert(isinstance(bird2, Bird)) assert(bird2.fly() == "No flying for me.") assert(bird2.swim() == "I can swim!") bird2.layEgg() assert(bird2.countEggs() == 1) assert(str(bird2) == "Emperor Penguin has 1 egg") assert(getLocalMethods(Penguin) == ['fly', 'swim']) # A MessengerBird is a Bird that can optionally carry a message bird3 = MessengerBird("War Pigeon", message="Top-Secret Message!") assert(type(bird3) == MessengerBird) assert(isinstance(bird3, MessengerBird)) assert(isinstance(bird3, Bird)) assert(not isinstance(bird3, Penguin)) assert(bird3.deliverMessage() == "Top-Secret Message!") assert(str(bird3) == "War Pigeon has 0 eggs") assert(bird3.fly() == "I can fly!") bird4 = MessengerBird("Homing Pigeon") assert(bird4.deliverMessage() == "") bird4.layEgg() assert(bird4.countEggs() == 1) assert(getLocalMethods(MessengerBird) == ['__init__', 'deliverMessage']) print("Done!")


3. recursive alternatingSum(lst) [10 pts]
   Write the function alternatingSum(lst) that takes a possibly-empty list of numbers, lst, and returns the alternating sum of the list, where every other value is subtracted rather than added. For example: alternatingSum([1,2,3,4,5]) returns 1-2+3-4+5 (that is, 3). If lst is empty, return 0.
   
   You must use recursion to solve this problem; using a for or while loop will result in the code failing on Autolab. You may also not use inherently iterative functions. These include range, sum, max, min, count, replace, sort, reverse, sorted, and reversed.


4. recursive powersOf3ToN(n) [15 pts]
   Write the function powersOf3ToN(n) that takes a possibly-negative float or int n, and returns a list of the positive powers of 3 up to and including n, or None (not an empty list) if no such values exist. As an example, powersOf3ToN(10.5) returns [1, 3, 9].
   
   You must use recursion to solve this problem; using a for or while loop will result in the code failing on Autolab. You may also not use inherently iterative functions. These include range, sum, max, min, count, replace, sort, reverse, sorted, and reversed.