C++ Primer Plus

The STL (see Chapter 16 and Appendix G, “The STL methods and Functions”) provides ready-made solutions to many programming needs, so you should use it. For example, instead of declaring an array of double or of string objects, you can create a vector object or a vector object. The advantages are similar to those of using string objects instead of C-style strings. Assignment is defined, so you can use the assignment operator to assign one vector object to another. You can pass a vector object by reference, and a function receiving such an object can use the size() method to determine the number of elements in the vector object. Built-in memory management allows for automatic resizing when you use the pushback() method to add elements to a vector object. And of course, several useful class methods and general algorithms are at your service. Or with C++11, if a fixed-size array is a better fit, use array or array.

If you need a list, a double-ended queue (or deque), a stack, a regular queue, a set, or a map, you should use the STL, which provides useful container templates. The algorithm library is designed so that you can easily copy the contents of a vector to a list or compare the contents of a set to a vector. This design makes the STL a toolkit that provides basic units that you can assemble as needed.

The extensive algorithm library was designed with efficiency as one of the main design goals, so you can get top-flight results with relatively little programming effort on your part. And the iterator concept used to implement the algorithms means that the algorithms aren’t limited to being used with STL containers. In particular, they can be applied to traditional arrays, too.

J. Answers to Chapter Reviews

Answers to Chapter Review for Chapter 2

1. They are called functions.

2. It causes the contents of the iostream file to be substituted for this directive before final compilation.

3. It makes definitions made in the std namespace available to a program.

4. cout << "Hello, world\n";

or

cout << "Hello, world" << endl;

5. int cheeses;

6. cheeses = 32;

7. cin >> cheeses;

8. cout << "We have " << cheeses << " varieties of cheese\n";

9. The function froop() expects to be called with one argument, which will be type double, and that the function will return a type int value. For instance, it could be used as follows:

int gval = froop(3.14159);

The function rattle() has no return value and expects an int argument. For instance, it could be used as follows:

rattle(37);

The function prune() returns an int and expects to be used without an argument. For instance, it could be used as follows:

int residue = prune();

10. You don’t have to use return in a function when the function has the return type void. However, you can use it if you don’t give a return value:

return;

Answers to Chapter Review for Chapter 3

1. Having more than one integer type lets you choose the type that is best suited to a particular need. For example, you could use short to conserve space or long to guarantee storage capacity or to find that a particular type speeds up a particular calculation.

2.

short rbis = 80;            // or short int rbis = 80;

unsigned int q = 42110;     // or unsigned q = 42110;

unsigned long ants = 3000000000;

// or long long ants = 3000000000;

Note: Don’t count on int being large enough to hold 3,000,000,000. Also if your system supports universal list-initialization, you could use it:

short rbis = {80};          // = is optional

unsigned int q {42110};     // could use = {42110}

long long ants {3000000000};

3. C++ provides no automatic safeguards to keep you from exceeding integer limits; you can use the climits header file to determine what the limits are.

4. The constant 33L is type long, whereas the constant 33 is type int.

5. The two statements are not really equivalent, although they have the same effect on some systems. Most importantly, the first statement assigns the letter A to grade only on a system using the ASCII code, while the second statement also works for other codes. Second, 65 is a type int constant, whereas 'A' is a type char constant.

6. Here are four ways:

char c = 88;

cout << c << endl;          // char type prints as character