CSC 2210, Hasker's Section: Exam 2 Review

The exam is closed-note, closed-book. If you need to know the name of a method (other than .begin, .end) in the STL, I will give that name to you.

• Note 6: C++ class introduction, std::string
  • Not: C-style strings
  • CPP, #include, #ifndef magic
  • Memory maps
  • declaring vs. defining variables, classes, methods, functions
  • review, but important here as well: scope (where accessible) vs lifetime (how long an identifier holds its value)
  • Declare identifier before can use it
  • Separating method definitions from declarations
  • Separate compilation with #include, linkers
• Note 7: Pointers and Classes
  • addresses, pointers, dereference, heap, stack, dangling pointer, memory leak
  • classes as the key feature of C++
  • creating your own built-in types through operator overloading
    • No expectation to define operators, but should understand them
    • Stack vs. heap declaration of objects
    • inline methods in classes, virtual, virtual functions, : public
    • const methods
    • default constructor
    • subclass
    • destructor, delete
  • Implementing growable arrays
  • Using pointers with domain classes (classes that are a necessary part of the problem, as opposed to classes that are part of a particular solution)
• Note 8: Floating-Point
  • 32-bit ieee 754 format, including special bit patterns
  • Be able to converting from the bit pattern to a value; you will not be tested on doing it the other way, but you should know the steps
  • not comparing with == except against 0.0
  • Understanding why addition is not associative for floats - that is, (a+b)+c != a+(b+c) in some cases
  • Rational for knowing floating-point representation
  • cost of floating-point operations - where are the loops?
  • single vs. double precision
  • understanding types: set of values, bit patterns, abstract data types; why are these important?
Note 9: Inheritance
• virtual methods, inheritance polymorphism, override
• more on declaration vs. definition
• pointers, destructors, delete
• abstract methods, classes, = 0
• vtables
• pass by const&
• namespaces
• organizing C++ projects, especially #includes
• Templates
  • template functions, type parameters, consistency of types
  • template classes, specializing by type and size
  • Java generics can hold objects of different types - unchecked containers
  • STL: list, vector, [] vs .at for vector
  • Key container operations: .begin, .end
  • other containers: map, stack
  • <algorithm>
  • duck typing in Python, static vs. dynamic typing, C++ STL
  • NOTE: some topics may be added

Exercises/Questions

1. Most phones have a simple app that allows you to take notes. Write a class Note that captures a note (a string) and timestamp (milliseconds since 00:00 on Jan. 1 1970). It should have a message to return the note text and a print() method that writes a formatted date followed by a newline followed by the note text and another newline. Assume the library function void prDate(int ms); does the appropriate formatting (but don't write this function). The constructor for the class should set both attributes.
   • Write the header file you would use for your class.
2. Write a class NoteBook that contains an arbitrary-sized collection of pointers to Note objects with a constructor that sets the collection to be empty, an add method that takes a pointer to a Note and adds it to the collection, and a print method that prints all notes. You can use the STL in your answer.
3. Implement a template Queue class in C++
   • Implement this as a linked list using the class

             class Node {
               Node *nextNode;
               ItemType _item;
             public:
               Node(ItemType item, Node *next = nullptr) : nextNode(next), _item(item) { }
               ItemType item() const { return _item; }
               Node* next() { return nextNode; }
             };
     

     Note your template type parameter should be named ItemType so you do not have to rewrite this class in your solution. Note you will need a pointer to the front of the list and the back of the list; new items will be added to the back (by a method add), old items removed from the front (by a method take). Include a method empty that returns true if the Queue has no items.
   • Implement a destructor for Queue.
   • What would happen if you passed a Queue by value? That is, what would be the impact of the code

             void pr(Queue<string> todo) {
                while ( !todo.empty() }
                  cout << todo.take() << endl;
             }
     

   • Would changing the prototype for pr to

             void pr(const Queue<string> &todo);
     

     fix this?
   • Add a method to Queue to remove all items matching a given target. For extra credit, the method should return the Node's to the heap.
4. Write a C++ function that takes a list<string> parameter and returns a new list with every other item. The function should run in O(n) time.
5. Using pointers, not indices, write C++ code to return a pointer to the first positive number in an array of doubles
6. Create a class A and a subclass B, both with virtual methods xyz, and draw their vtables. Add a virtual method uvw for B and a virtual method abc for A, and add these to the vtables.
7. Some argue all methods in C++ classes should be virtual. Why? Why not? There should be at least two reasons on the negative side.
8. Why should inline code be in header files?
9. Why are IEEE Std 754 floats implemented using three fields? (Note programmers can write code without being aware of these fields, but they are critical to understanding details about floating-point numbers.)

Code snippets related to these are available.