C++ Primer Plus

// Version 1

while (cin.get(ch))    // quit on eof

{

      if (ch == ' ')

             spaces++;

      if (ch == '\n')

            newlines++;

}

// Version 2

while (cin.get(ch))    // quit on eof

{

      if (ch == ' ')

            spaces++;

      else if (ch == '\n')

            newlines++;

}

What advantages, if any, does the second form have over the first?

2. In Listing 6.2, what is the effect of replacing ++ch with ch+1?

3. Carefully consider the following program:

#include

using namespace std;

int main()

{

    char ch;

    int ct1, ct2;

    ct1 = ct2 = 0;

    while ((ch = cin.get()) != '$')

    {

        cout << ch;

        ct1++;

        if (ch = '$')

            ct2++;

        cout << ch;

    }

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

    return 0;

}

Suppose you provide the following input, pressing the Enter key at the end of each line:

Hi!

Send $10 or $20 now!

What is the output? (Recall that input is buffered.)

4. Construct logical expressions to represent the following conditions:

a. weight is greater than or equal to 115 but less than 125.

b. ch is q or Q.

c. x is even but is not 26.

d. x is even but is not a multiple of 26.

e. donation is in the range 1,000–2,000 or guest is 1.

f. ch is a lowercase letter or an uppercase letter. (Assume, as is true for ASCII, that lowercase letters are coded sequentially and that uppercase letters are coded sequentially but that there is a gap in the code between uppercase and lowercase.)

5. In English, the statement “I will not not speak” means the same as “I will speak.” In C++, is !!x the same as x?

6. Construct a conditional expression that is equal to the absolute value of a variable. That is, if a variable x is positive, the value of the expression is just x, but if x is negative, the value of the expression is -x, which is positive.

7. Rewrite the following fragment using switch:

if (ch == 'A')

    a_grade++;

else if (ch == 'B')

    b_grade++;

else if (ch == 'C')

    c_grade++;

else if (ch == 'D')

    d_grade++;

else

    f_grade++;

8. In Listing 6.10, what advantage would there be in using character labels, such as a and c, instead of numbers for the menu choices and switch cases? (Hint: Think about what happens if the user types q in either case and what happens if the user types 5 in either case.)

9. Consider the following code fragment:

int line = 0;

char ch;

while (cin.get(ch))

{

    if (ch == 'Q')

           break;

    if (ch != '\n')

           continue;

    line++;

}

Rewrite this code without using break or continue.

Programming Exercises

1. Write a program that reads keyboard input to the @ symbol and that echoes the input except for digits, converting each uppercase character to lowercase, and vice versa. (Don’t forget the cctype family.)

2. Write a program that reads up to 10 donation values into an array of double. (Or, if you prefer, use an array template object.) The program should terminate input on non-numeric input. It should report the average of the numbers and also report how many numbers in the array are larger than the average.

3. Write a precursor to a menu-driven program. The program should display a menu offering four choices, each labeled with a letter. If the user responds with a letter other than one of the four valid choices, the program should prompt the user to enter a valid response until the user complies. Then the program should use a switch to select a simple action based on the user’s selection. A program run could look something like this:

Please enter one of the following choices:

c) carnivore           p) pianist

t) tree                g) game

f

Please enter a c, p, t, or g: q

Please enter a c, p, t, or g: t

A maple is a tree.

4. When you join the Benevolent Order of Programmers, you can be known at BOP meetings by your real name, your job title, or your secret BOP name. Write a program that can list members by real name, by job title, by secret name, or by a member’s preference. Base the program on the following structure:

// Benevolent Order of Programmers name structure

struct bop {

    char fullname[strsize]; // real name

    char title[strsize];    // job title

    char bopname[strsize];  // secret BOP name

    int preference;         // 0 = fullname, 1 = title, 2 = bopname

};

In the program, create a small array of such structures and initialize it to suitable values. Have the program run a loop that lets the user select from different alternatives:

a. display by name     b. display by title

c. display by bopname  d. display by preference

q. quit

Note that “display by preference” does not mean display the preference member; it means display the member corresponding to the preference number. For instance, if preference is 1, choice d would display the programmer’s job title. A sample run may look something like the following:

Benevolent Order of Programmers Report

a. display by name     b. display by title

c. display by bopname  d. display by preference

q. quit

Enter your choice: a

Wimp Macho

Raki Rhodes

Celia Laiter

Hoppy Hipman

Pat Hand

Next choice: d

Wimp Macho

Junior Programmer

MIPS

Analyst Trainee

LOOPY

Next choice: q

Bye!

5. The Kingdom of Neutronia, where the unit of currency is the tvarp, has the following income tax code:

First 5,000 tvarps: 0% tax