C++ Primer Plus

The sstream header file defines istringstream and ostringstream classes that let you use istream and ostream methods to extract information from a string and to format information placed into a string.

Chapter Review

1. What role does the iostream file play in C++ I/O?

2. Why does typing a number such as 121 as input require a program to make a conversion?

3. What’s the difference between the standard output and the standard error?

4. Why is cout able to display various C++ types without being provided explicit instructions for each type?

5. What feature of the output method definitions allows you to concatenate output?

6. Write a program that requests an integer and then displays it in decimal, octal, and hexadecimal forms. Display each form on the same line, in fields that are 15 characters wide, and use the C++ number base prefixes.

7. Write a program that requests the following information and that formats it as shown:

Enter your name: Billy Gruff

Enter your hourly wages: 12

Enter number of hours worked: 7.5

First format:

                   Billy Gruff: $     12.00:  7.5

Second format:

Billy Gruff                   : $12.00     :7.5

8. Consider the following program:

//rq17-8.cpp

#include

int main()

{

    using namespace std;

    char ch;

    int ct1 = 0;

    cin >> ch;

    while (ch != 'q')

    {

        ct1++;

        cin >> ch;

    }

    int ct2 = 0;

    cin.get(ch);

    while (ch != 'q')

    {

        ct2++;

        cin.get(ch);

    }

    cout << "ct1 = " << ct1 << "; ct2 = " << ct2 << "\n";

    return 0;

}

What does it print, given the following input:

I see a q

I see a q

Here signifies pressing the Enter key.

9. Both of the following statements read and discard characters up to and including the end of a line. In what way does the behavior of one differ from that of the other?

while (cin.get() != '\n')

    continue;

cin.ignore(80, '\n');

Programming Exercises

1. Write a program that counts the number of characters up to the first $ in input and that leaves the $ in the input stream.

2. Write a program that copies your keyboard input (up to the simulated end-of-file) to a file named on the command line.

3. Write a program that copies one file to another. Have the program take the filenames from the command line. Have the program report if it cannot open a file.

4. Write a program that opens two text files for input and one for output. The program should concatenate the corresponding lines of the input files, use a space as a separator, and write the results to the output file. If one file is shorter than the other, the remaining lines in the longer file should also be copied to the output file. For example, suppose the first input file has these contents:

eggs kites donuts

balloons hammers

stones

And suppose the second input file has these contents:

zero lassitude

finance drama

The resulting file would have these contents:

eggs kites donuts zero lassitude

balloons hammers finance drama

stones

5. Mat and Pat want to invite their friends to a party, much as they did in Programming Exercise 8 in Chapter 16, except now they want a program that uses files. They have asked you to write a program that does the following:

• Reads a list of Mat’s friends’ names from a text file called mat.dat, which lists one friend per line. The names are stored in a container and then displayed in sorted order.

• Reads a list of Pat’s friends’ names from a text file called pat.dat, which lists one friend per line. The names are stored in a container and then displayed in sorted order.

• Merges the two lists, eliminating duplicates and stores the result in the file matnpat.dat, one friend per line.

6. Consider the class definitions of Programming Exercise 5 in Chapter 14, “Reusing Code in C++”. If you haven’t yet done that exercise, do so now. Then do the following:

Write a program that uses standard C++ I/O and file I/O in conjunction with data of types employee, manager, fink, and highfink, as defined in Programming Exercise 5 in Chapter 14. The program should be along the general lines of Listing 17.17 in that it should let you add new data to a file. The first time through, the program should solicit data from the user, show all the entries, and save the information in a file. On subsequent uses, the program should first read and display the file data, let the user add data, and show all the data. One difference is that data should be handled by an array of pointers to type employee. That way, a pointer can point to an employee object or to objects of any of the three derived types. Keep the array small to facilitate checking the program; for example, you might limit the array to 10 elements:

const int MAX = 10;     // no more than 10 objects

...

employee * pc[MAX];