### Adding an Element to a Collection

To add an element to a collection, call the add function. Consider the following example:

    //main.cpp - main file
    #include <iset.h>
    #include <iostream.h>
    #include "person.h"   //person.h from the previous examples

    typedef ISet<Person> AddressList;

    void main()
    {
        AddressList Business;
        Person A("Peter Black","714-50706");
        Person B("Carl Render","714-540321");
        Person C("Sandra Summers","214-660012");
        Business.add(A);
        Business.add(B);
        Business.add(C);
        Business.add(A);            //Person A is added for the second time
        cout << "\nThe set now contains " << Business.numberOfElements()
            <<" entries!\n";
    }

If you run the program, the set will only contain 3 different entries. In a set, each element is unique. No two elements can be the same. To illustrate the difference between sets and bags, run the program using a bag rather than a set.

Introduction to the Collection Classes
Adding Elements
Removing Elements
Replacing Elements

Class Template Naming Conventions
Possible Implementation Paths
Choosing One of the Provided Implementation Variants
Removing an Element from a Collection
Taking Advantage of the Abstract Class Hierarchy
Using Collection Notification
Instantiating the Collection Classes
Troubleshooting Problems while Using the Collection Class Library