Applying the first-class function and the pure function to the immutable object

We gained an introduction to the immutable object from the preceding discussion. As you learned in the previous chapter, we can take advantage of the first-class function and pure function to create an immutable programming approach. Let's borrow the code from Chapter 2, Manipulating Functions in Functional Programming, that is first_class_1.cpp. We will have the addition(), subtraction(), multiplication(), and division() methods in our following first_class_pure_immutable.cpp code. We will then invoke the pure function on the class and assign the result to the variable. The code is written as follows:

    /* first_class_pure_immutable.cpp */
    #include <iostream>

    using namespace std;

    // MyValue class stores the value
    class MyValue
    {
      public:
        const int value;
    ...