Laboratory Exercise Week 9 solution

Task One: A singleton
Implement a singleton class in Single.cpp. In a singleton we are only allowed one instance of the class to exist at a time. Your class should record how many attempts to create instances have occurred. Your class should request from the user whether to create an instance (2), destroy an instance (1) or exit (0).
Sample input and output are provided in Input_Single.txt and Single.txt, respectively.
Task Two: Namespace and a template class - Bag
Define a template class Bag in a file Bag.h that belongs to a namespace MYLIB. A Bag is a collection of zero or more elements, in no particular order that may have duplicates. The public interface consists of methods to:
 Create a template class Bag.
 A function add() which can add an element to a Bag.
 A function remove() which can remove a given element from a Bag. If the element is duplicated, only remove the first one.
 Implement the union of two Bag objects in an overloaded + operator. The union of two Bag objects, b1 and b2, should be a Bag object containing elements that belong to b1 or b2. Remember that duplication is fine.
 An insertion operator (<<) that print all the elements in the Bag.
Implement member functions and insertion operator for the Bag in a file Bag.cpp.
Download the file testBag.cpp in which instantiates and initialize two integer Bag objects and two double Bag objects to test your Bag class.
Compile the program as
CC testBag.cpp Bag.cpp
and run the program.
Number of integers for an integer bag 1: 5
Input an integer: 1
Input an integer: 3
Input an integer: 4
Input an integer: 6
Input an integer: 9
The first integer bag contains: 1 3 4 6 9
Number of integers for an integer bag 2: 3
Input an integer: 1
Input an integer: 6
Input an integer: 8
The second integer bag contains: 1 6 8
Combine two integer bags: 1 3 4 6 9 1 6 8
Input the element that needs to be removed: 1
After the element 1 has been removed, the bag contains 3 4 6 9 1 6 8
Input the element that needs to be removed: 6
After the element 6 has been removed, the bag contains 3 4 9 1 6 8
Number of doubles for a double bag 1: 6
Input a double: 1.5
Input a double: 2.2
Input a double: 3.2
Input a double: 1.5
Input a double: 2.4
Input a double: 2.2
The first double bag contains: 1.5 2.2 3.2 1.5 2.4 2.2
Number of doubles for a double bag 2: 4
Input a double: 2.2
Input a double: 3.3
Input a double: 4.1
Input a double: 3.2
The second double bag contains: 2.2 3.3 4.1 3.2
Combine two double bags: 1.5 2.2 3.2 1.5 2.4 2.2 2.2 3.3 4.1 3.2
Input the element that needs to be removed: 1.5
After the element 1.5 has been removed, the bag contains 2.2 3.2 1.5 2.4 2.2 2.2 3.3 4.1 3.2
Input the element that needs to be removed: 4.1
After the element 4.1 has been removed, the bag contains 2.2 3.2 1.5 2.4 2.2 2.2 3.3 3.2
You can download input_bag.txt to test your program by
./a.out < input_bag.txt