5.9. Chapter Review QuestionsΒΆ

  1. Which of these are Boolean expressions? Assume the variables are of type int:

    true
    "false"
    x = 3
    n < 10
    count == 22
    x <= 2 || x > 10
    x == 2 || 3
    1 < y < 10
    
  2. What are the values of these expressions? Be able to explain:

    2 < 3 && 4 < 5
    2 < 3 && 4 < 3
    2 < 3 || 4 < 5
    2 < 3 || 4 < 3
    3 < 2 || 4 < 3
    2 < 3 || 4 < 5 && 4 < 3
    
  3. Correct the last two entries in the first problem, supposing the user meant “x could be either 2 or 3” and then “y is strictly between 1 and 10”.

  4. Add parentheses in 2 < 3 || 4 < 5 && 4 < 3 to get a different result.

  5. Suppose you have four possible distinct situations in your algorithm, each requiring a totally different response in your code, and exactly one of the situations is sure to occur. Have many times must you have if followed by a condition?

  6. Suppose you have four possible distinct situations in your algorithm, each requiring a totally different response in your code, and at most one of the situations will occur, so possibly nothing will happen that needs a response at all. Have many times must you have if followed by a condition?

  7. Assume IsBig(x) returns a Boolean value. Remove the redundant part of this statement:

    if (IsBig(x) == true)
       x = 3;
    
  8. Write an equivalent (and much shorter!) statement with no if:

    if (x > 7)
       return true;
    else
       return false;
    
  9. Write an equivalent (and much shorter!) statement with no if:

    if (x > 7)
       isSmall = false;
    else
       isSmall = true;
    
  10. Assume x and y are local int variables. Code fragments are separated by a blank line below. Pairs of the fragments are logically equivalent, but not necessarily with a directly adjacent fragment. Match the pairs. Be sure you understand when different pairs would behave differently. Caution: there is some pretty awful code here, that we would hope you would never write, but you might need to correct/read! Think of pitfalls. In each equivalent pair, which code fragment is more professional?

    if (x > 7) {    //a
       x = 5;
    }
    y = 1;
    
    if (x > 7) {    //b
       x = 5;
       y = 1;
    }
    
    if (x > 7)      //c
       x = 5;
       y = 1;
    
    if (x > 7) {    //d
       x = 5;
    }
    else {
       y = 1;
    }
    
    if (x > 7)      //e
       x = 5;
    else if (x <= 7) {
       y = 1;
    }
    
    if (x > 7) {    //f
       y = 1;
    }
    if (x > 7) {
       x = 5;
    }
    
  11. Same situation as the last problem, and same caution, except this time assume the fragments appear in a function that returns an int. In each pair of equivalent fragments, which is your preference?

    y = 1;         //a
    if (x > 7) {
       return x;
    }
    
    if (x > 7) {   //b
       return x;
    }
    y = 1;
    
    if (x > 7) {   //c
       return x;
    }
    else {
       y = 1;
    }
    
    if (x > 7) {   //d
       return x;
       y = 1;
    }
    
    if (x > 7) {   //e
       y = 1;
       return x;
    }
    y = 1;
    
    if (x > 7) {   //f
       return x;
    }
    
    if (x > 7);    //g
       return x;
    
    return x;      //h
    
  12. Same situation as the last problem, and same caution:

    if (x > 5)        //a
       if (x > 7)
           return x;
    else
       y = 1;
    
    if (x > 5)  {     //b
       if (x > 7)
           return x;
    }
    else {
       y = 1;
    }
    
    if (x > 7)        //c
       return x;
    if (x <= 5)
       y = 1;
    
    if (x > 7)        //d
       return x;
    if (x > 5)
       y = 1;
    
  13. When reading a verbal description of a problem to solve, what are some words or phrases that suggest that some version of an if statement will be useful?