**********  July 9th lab - review of theSum.p code   **********   

    **********  Two group exercises: writing functions   **********   

chaos:~/web/perl$   cat theSum.p     <-------- Could also use more theSum.p
                                                              -------------
# Written on Monday, July 9th, 2001 for 810:088 lab class session
#        and Tuesday followup lecture/discussion.

# This program defines two different functions, theSum and theProduct
#                                               ------     ----------
# Filename:  theSum.p 

sub theSum;  sub theProduct;

@a = (11, 22, 33, 44, 55);

$numbers = join (" + ", @a);

$numbers = "(" . $numbers . ")";

$answer = theSum(@a, $numbers);    # Note:  Two arguments are input
                                   #        to theSum() function....

print "\nThe sum ($numbers) is $answer.\n";

$numbers = join (" * ", @a);

print "\nThe product ($numbers) is " . theProduct(@a) . ".\n\n";


##########################################################################
# theSum is a Function (read Hour 8) or a Subroutine (read chapter 13)   #
#                                                                        #
# Input: Argument #1:  A list (array) of numbers                         #
#        Argument #2:  A string formatted list of the numbers, to echo   #
#                      out the values in whatever format the user wants  #
#                                                                        #
# Output: Returns the sum of the list of values, and                     #
#         prints to STDOUT the formatted list.                           # 
##########################################################################

sub theSum
{
   print "\n ****** Entering theSum function ****** \n";

   $string = pop @_;   # remove the last element from the array @_
                       #   this was the 2nd argument in the call.

   @array = @_;        # what is left is the list of numbers passed
                       #   as the 1st argument in calling theSum().
   $s = 0;
   print "\nThe popped value was ---> $string \n";

   foreach $element (@array) { $s += $element; }

   print "\n ****** Leaving theSum and returning a value ****** \n";

   return $s;
}






########################################################################
# Function theProduct                                                  #
#          ----------       Input:  An array of numeric values         #
#                          Output:  Product of the values              #
#                                                                      #
########################################################################

sub theProduct
{
    @a = @_;

    $p = 1;

    foreach $value (@a)
    {
       $p = $p * $value;
    }
    return $p;
}


chaos:~/web/perl$   perl theSum.p

****** Entering theSum function ******

The popped value was ---> (11 + 22 + 33 + 44 + 55) 

****** Leaving theSum and returning a value ******

The sum ((11 + 22 + 33 + 44 + 55)) is 165.

The product (11 * 22 * 33 * 44 * 55) is 19326120.


--------------------------------------------------------------------------

  1.  Write a function that would return 1 (True) if the list
      a numbers is sorted into ascending order, and 0 (False) otherwise.

      if ( ascending(@a) )
      {
         $m = "The list is sorted ";
      }
      else
      {
         $m = "The list is NOT sorted ";
      }
      $m .= "in ASCENDING order.\n";
      print $m;

   
  2.  Write a function that would remove all of the negative numbers
      from the list.  

      For example:   @a = (11, -22, 33, -44, 55);
                     @a = removeNegativeValues(@a);
                     print "Here is array \@a with minus values gone: " .
                           "@a \n";