C++ Primer Plus

3. Modify Listing 11.15 so that instead of reporting the results of a single trial for a particular target/step combination, it reports the highest, lowest, and average number of steps for N trials, where N is an integer entered by the user.

4. Rewrite the final Time class example (Listings 11.10, 11.11, and 11.12) so that all the overloaded operators are implemented using friend functions.

5. Rewrite the Stonewt class (Listings 11.16 and 11.17) so that it has a state member that governs whether the object is interpreted in stone form, integer pounds form, or floating-point pounds form. Overload the << operator to replace the show_stn() and show_lbs() methods. Overload the addition, subtraction, and multiplication operators so that one can add, subtract, and multiply Stonewt values. Test your class with a short program that uses all the class methods and friends.

6. Rewrite the Stonewt class (Listings 11.16 and 11.17) so that it overloads all six relational operators. The operators should compare the pounds members and return a type bool value. Write a program that declares an array of six Stonewt objects and initializes the first three objects in the array declaration. Then it should use a loop to read in values used to set the remaining three array elements. Then it should report the smallest element, the largest element, and how many elements are greater or equal to 11 stone. (The simplest approach is to create a Stonewt object initialized to 11 stone and to compare the other objects with that object.)

7. A complex number has two parts: a real part and an imaginary part. One way to write an imaginary number is this: (3.0, 4.0). Here 3.0 is the real part and 4.0 is the imaginary part. Suppose a = (A,Bi) and c = (C,Di). Here are some complex operations:

• Addition: a + c = (A + C, (B + D)i)

• Subtraction: a - c = (A - C, (B - D)i)

• Multiplication: a × c = (A × C - B×D, (A×D + B×C)i)

• Multiplication: (x a real number): x × c = (x×C,x×Di)

• Conjugation: ~a = (A, - Bi)

Define a complex class so that the following program can use it with correct results:

#include

using namespace std;

#include "complex0.h"  // to avoid confusion with complex.h

int main()

{

    complex a(3.0, 4.0);   // initialize to (3,4i)

    complex c;

    cout << "Enter a complex number (q to quit):\n";

    while (cin >> c)

    {

        cout << "c is " << c << '\n';

        cout << "complex conjugate is " << ~c << '\n';

        cout << "a is " << a << '\n";

        cout << "a + c is " << a + c << '\n';

        cout << "a - c is " << a - c << '\n';

        cout << "a * c is " << a * c << '\n';

        cout << "2 * c is " << 2 * c << '\n';

        cout << "Enter a complex number (q to quit):\n";

    }

    cout << "Done!\n";

    return 0;

}

Note that you have to overload the << and >> operators. Standard C++ already has complex support—rather more extensive than in this example—in a complex header file, so use complex0.h to avoid conflicts. Use const whenever warranted.

Here is a sample run of the program:

Enter a complex number (q to quit):

real: 10

imaginary: 12

c is (10,12i)

complex conjugate is (10,-12i)

a is (3,4i)

a + c is (13,16i)

a - c is (-7,-8i)

a * c is (-18,76i)

2 * c is (20,24i)

Enter a complex number (q to quit):

real: q

Done!

Note that cin >> c, through overloading, now prompts for real and imaginary parts.

12. Classes and Dynamic Memory Allocation

In this chapter you’ll learn about the following:

• Using dynamic memory allocation for class members

• Implicit and explicit copy constructors

• Implicit and explicit overloaded assignment operators

• What you must do if you use new in a constructor

• Using static class members

• Using placement new with objects

• Using pointers to objects

• Implementing a queue abstract data type (ADT)

This chapter looks at how to use new and delete with classes and how to deal with some of the subtle problems that using dynamic memory can cause. This may sound like a short list of topics, but these topics affect constructor design, destructor design, and operator overloading.

Let’s look at a specific example of how C++ can add to your memory load. Suppose you want to create a class with a member that represents someone’s last name. The simplest, most primitive way is to use a character array member to hold the name. But this has some drawbacks. You might use a 14-character array and then run into Bartholomew Smeadsbury-Crafthovingham. Or to be safer, you might use a 40-character array. But if you then create an array of 2,000 such objects, you’ll waste a lot of memory with character arrays that are only partly filled. (At that point, you’re adding to the computer’s memory load.) There is an alternative.