Topical Information

Here are a few questions to help you clarify your understanding of advanced branching — switches and the ?: operator.

Question Set Information

Questions

1. A ?: operation can typically replace an if structure when _____. (Hint: there may be more than one.)

   1. the if is 1-wayNO
   2. the if is 2-wayYES
   3. each branch involves multiple statementsNO
   4. the branches involve different types of valuesNO
   5. the branches perform the same operation to the valuesYES

2. Rewrite the following if structure as a ?: operation. (Hints: Nesting may be required... There should be only one cout statement when you are done.)

   
       cout << "Your value is ";
       if (x > 0)
       {
           cout << "positive";
       }
       else if (x < 0)
       {
           cout << "negative";
       }
       else
       {
           cout << "zero";
       }
       cout << ".\n";
   

   
       cout << "Your value is "
            << (x > 0 ? "positive" :
                      (x < 0 ? "negative" : 
                                  "zero"))
            << ".\n";
   
   

3. What conditions are necessary for a branching structure (like a cascading if, for instance) to be replaced by a switch structure? (Hint: There are at least four...but there could be as many as seven!)

   
           
   
           
   all comparisons are for equality (==)
           
   a common expression (CE) is involved in all comparisons
           
   the other expression in all these comparisons must be a
               constant or literal expression
           
   the CE and the constant/literal expressions must be of a
               [one-dimensional] discrete type
           
   the constant/literal expressions must all be unique
           
   there can be multiple equality tests combined with logical or
               (¦¦) on a branch
           
   there can be an else clause at the end of the branching
               structure
           
   
   

4.  

   TRUE✗		FALSE✓		Only if structures can be nested: ?: and switches are too complicated.
   TRUE✗		FALSE✓		You can't mix different structures when nesting: an if inside a switch or a switch inside an if.
   TRUE✗		FALSE✓		And, whatever you do, never try to nest a loop inside a branch or vice-versa! That is just WAY too confusing!

5. Write a switch structure to print the average score of the grade-range when you are given the user's letter grade. (i.e. If they enter 'A', you'd print 95, etc.)

   
           switch (grade)
           {
               case 'A': score = 95; break;
               case 'B': score = 85; break;
               case 'C': score = 75; break;
               case 'D': score = 65; break;
               case 'F': score = 30; break;
               default: score = -1; break;
           }
   
   

6. Write a switch structure to calculate the number of days since the last Dec 31^st. The current month, day of the month, and year are in those respective variables. Store the calculated number of days in that (<--) variable.

   
           days = day;
           switch (month-1)
           {
               case 11: days += 30;
               case 10: days += 31;
               case  9: days += 30;
               case  8: days += 31;
               case  7: days += 31;
               case  6: days += 30;
               case  5: days += 31;
               case  4: days += 30;
               case  3: days += 31;
               case  2: days += 28;
               case  1: days += 31;
           }
           if ( month > 2 &&
                year % 4 == 0 &&
                (year % 100 != 0 ¦¦
                 year % 400 == 0))
           {
               days++;
           }