IWA-HWG Perl Course. Week 3 Quiz

1. When perl is expecting a list, how do you force scalar context? Provide a sample.
   
   If a list variable is used as a scalar, then the result is the number of elements in the list (or one more than the highest index of the list if the elements were assigned non-consecutively). Using the word "scalar" in front of the list forces it to be interpreted as a scalar as shown below. (Learning Perl, p. 51)

           @group = qw( Peter Paul Mary);
           print "The highest index is $#group.\n";
           print "The group members are @group.\n";
           print "The group has ", scalar @group, " members.\n";
   
           $group2[0]="John";
           $group2[2]="Michelle";
           $group2[4]="Cass";
           $group2[6]="Denny";
           print "The highest index is $#group2.\n";
           print "The group members are @group2.\n";
           print "The group has ", scalar @group2, " members.\n";
       

   Result:
   
   
   
2. What is perl's favorite default when omitting a control variable from a loop? Show an example of its use:
   
   In the example below the statement foreach (3..20) sets up a for loop that goes from 3 up to and including 20. There is an implied counting variable. If the programmer wants to use the implied counter explicitly, he or she can use the default variable $_. (Learning Perl, p. 47)

       $fib1 = 1;
       $fib2 = 1;
   	
       print "1.\t$fib1\n";
       print "2.\t$fib2\n";	
       foreach (3..20)
       {
           ($fib1, $fib2) = ($fib2, $fib1+$fib2);
           print "$_.\t$fib2\n";	
       }
       

   Result:
   
   
   
3. How do you get the last element index of an array?
   
   Placing a dollar sign ($) followed by a pound sign (#) in front of the name of an array provides the highest index of the array. (Learning Perl, p. 40). For example, the lines

           @group = qw( Peter Paul Mary);
           print "The highest index is $#group.\n";
       

   yield the output: The highest index is 2.
   
   
4. Which perl function is used to examine every element of a hash?
   
   The each function uses a hash's internal iterator to step through and return key/value pairs -- one pair at a time. For example

           while( ($key, $value) = each %ENV)
           {
               print "$key => $value\n";
           }
       

   prints out the contents of the environment hash.