Chapter 5 Statements

Exercise 5.1:What is a null statement? When might you use a null statement?

Exercise 5.2: What is a block? When might you might use a block?

Exercise 5.3: Use the comma operator (§ 4.10, p. 157) to rewrite the while loop from§ 1.4.1 (p. 11) so that it no longer requires a block. Explain whether this rewrite im-proves or diminishes the readability of this code.

Exercise 5.4: Explain each of the following examples, and correct any problems you detect.

(a) while (string::iterator iter != s.end()) { /* . . . */ } 
(b) while (bool status = find(word)) { /* . . . */ }
if(!status){/* ... */}

Exercise 5.5: Using an if–else statement, write your own version of the program togenerate the letter grade from a numeric grade.

Exercise 5.6: Rewrite your grading program to use the conditional operator (§ 4.7,p. 151) in place of the if–else statement.

Exercise 5.7: Correct the errors in each of the following code fragments:

(a) if (ival1 != ival2) 
          ival1 = ival2
    else ival1 = ival2 = 0; 
(b) if (ival < minval) 
          minval = ival;
        occurs = 1;
(c) if (int ival = get_value())
        cout << "ival = " << ival << endl; 
    if (!ival)
        cout << "ival = 0\n"; 
(d) if (ival = 0)
    ival = get_value();

Exercise 5.9: Write a program using a series of if statements to count the number ofvowels in text read from cin.

Exercise 5.10: There is one problem with our vowel-counting program as we’ve im-plemented it: It doesn’t count capital letters as vowels. Write a program that countsboth lower- and uppercase letters as the appropriate vowel—that is, your programshould count both ’a’ and ’A’ as part of aCnt, and so forth.

Exercise 5.11: Modify our vowel-counting program so that it also counts the numberof blank spaces, tabs, and newlines read.

Exercise 5.12: Modify our vowel-counting program so that it counts the number ofoccurrences of the following two-character sequences: ff, fl, and fi.

Exercise 5.13: Each of the programs in the highlighted text on page 184 contains acommon programming error. Identify and correct each error.

Exercise 5.14: Write a program to read strings from standard input looking for duplicated words. The program should find places in the input where one word is followed immediately by itself. Keep track of the largest number of times a single repetition occurs and which word is repeated. Print the maximum number of duplicates, or else print a message saying that no word was repeated. For example, if the input is how now now now brown cow cowthe output should indicate that the word now occurred three times.

Exercise 5.15: Explain each of the following loops. Correct any problems you detect.

(a) for(intix=0;ix!=sz;++ix) {/* ... */} if (ix != sz)
    // . . . 
(b) int ix;
    for(ix!=sz;++ix){/* ... */}
(c) for(intix=0;ix!=sz;++ix,++sz) {/* ... */}

Exercise 5.16: The while loop is particularly good at executing while some conditionholds; for example, when we need to read values until end-of-file. The for loop isgenerally thought of as a step loop: An index steps through a range of values in acollection. Write an idiomatic use of each loop and then rewrite each using the otherloop construct. If you could use only one loop, which would you choose? Why?

Exercise 5.17: Given two vectors of ints, write a program to determine whetherone vector is a prefix of the other. For vectors of unequal length, compare the num-ber of elements of the smaller vector. For example, given the vectors containing 0,1, 1, and 2 and 0, 1, 1, 2, 3, 5, 8, respectively your program should return true.

Exercise 5.18: Explain each of the following loops. Correct any problems you detect.

(a) do
    int v1, v2;
    cout << "Please enter two numbers to sum:" ; 
    if (cin >> v1 >> v2)
    cout << "Sum is: " << v1 + v2 << endl; while (cin);
(b) do {
        // . . .
    } while (int ival = get_response()); 
(c) do {
        int ival = get_response();
    } while (ival);

Exercise 5.19: Write a program that uses a do while loop to repetitively request two strings from the user and report which string is less than the other.

Exercise 5.20: Write a program to read a sequence of strings from the standard input until either the same word occurs twice in succession or all the words have been read. Use a while loop to read the text one word at a time. Use the break statement to terminate the loop if a word occurs twice in succession. Print the word if it occurs twice in succession, or else print a message saying that no word was repeated.

Exercise 5.21: Revise the program from the exercise in § 5.5.1 (p. 191) so that it looks only for duplicated words that start with an uppercase letter.

Exercise 5.22: The last example in this section that jumped back to begin could be better written using a loop. Rewrite the code to eliminate the goto.

Exercise 5.23: Write a program that reads two integers from the standard input andprints the result of dividing the first number by the second.

Exercise 5.24: Revise your program to throw an exception if the second number iszero. Test your program with a zero input to see what happens on your system if youdon’t catch an exception.

Exercise 5.25: Revise your program from the previous exercise to use a try block tocatch the exception. The catch clause should print a message to the user and askthem to supply a new number and repeat the code inside the try.

Notes