Project 3 Notes

Project 3 Notes

(Monday 11/16) I have added a new sample input file sample.in3.data, and the corresponding output for min_sup=0.075 in sample.in3.output.0.075. Make sure your program works on this larger data file, which is in /dept/cs/cs230/public/projects/project3/ directory.
(Tuesday 11/10) In main.cpp make sure that all ifstream are preceded by std::, otherwise you'll get compiler errors in VC++. You also need to include "sstream" header file for VC++, plus some other header files. This has been fixed in the main.cpp file.
(Sunday 11/8) Rename the function "union" as "wunion" in main.cpp. Since "union" is a C++ keyword, your compiler may generate errors.
(Friday 11/6) The call in the main program
```
    printFK(FK, 1);
```
should instead be
```
    printFK(*FK, 1);
```
(Friday 11/6) Note: you may have to change some or all of the classes provided to you. In particular, you will need to add to the Wordset class!
(Thursday 11/5) The HashTree class does NOT need to be a templated class! The type stored in the list at leaf nodes should be Wordset*. We have NOT changed the pseudocode and will not at this point. Each group can make its own changes.
(Thursday 11/5 and Friday 11/6) The declaration inside the HT_Node class
```
    HT_Node ** HashTable;
```
seems to be causing some confusion. Here's some help.
HashTable should be thought of as a dynamically allocated array of pointers to HT_Node's. When an HT_Node is converted from a leaf to an internal node, it will need an array of pointers to its children HT_Node's. This allocation is done by
```
    HashTable = new HT_Node*[HashTree::HashTableSize];
```
You can then treat HashTable as an array, filling in the pointers to its children.
(Thursday 11/5) The notion of a static member variable in a class seems to be new to some students. Well, you can think of it as a global variable for each class, allocated only once instead of once per class object. It needs to be initialized outside the class, but it can be changed inside of any member function (including, of course, the constructors). It can also be accessed by friends of the class without having a particular instance of the class. This is important for the HT_Node's to get global information about the tree, as in the allocation for HashTable above. The constructor for the HashTree will need to set the static variables appropriately. This could cause a problem for this project, so make sure, as in the pseudo-code, that each tree is deleted before the next tree is created.
Here is a simple example illustrating some of the features of static member variables.
```
    class Foo {
      friend class Grog;
    public:
      Foo() { Bar=1; x=5; }
    private:
      static int Bar;
      int x;
    };
    
    int Foo::Bar = 5;
    
    class Grog {
    public:
      Grog() {};
      void PrintBar() { std::cout << "In Grog: " << Foo::Bar << std::endl; }
    };
    
    int
    main ()
    {
      Grog g;
      g.PrintBar();  // outputs 5
      Foo f;
      g.PrintBar();  // outputs 1
    }
```