
<ul><h2><a name=11> * ARRAY VARIABLES * </a></h2></ul>


   A slightly more interesting kind of variable is the array variable
   which is a list of scalars (ie numbers and strings). Array variables
   have the same format as scalar variables except that they are prefixed
   by an @ symbol. The statement

@food  = ("apples", "pears", "eels");
@music = ("whistle", "flute");

   assigns a three element list to the array variable @food and a two
   element list to the array variable @music.

   The array is accessed by using indices starting from 0, and square
   brackets are used to specify the index. The expression

$food[2]

   returns eels. Notice that the @ has changed to a $ because eels is a
   scalar.


<ul><h2><a name=12>Array assignments</a></h2></ul>

   As in all of Perl, the same expression in a different context can
   produce a different result. The first assignment below explodes the
   @music variable so that it is equivalent to the second assignment.

@moremusic = ("organ", @music, "harp");
@moremusic = ("organ", "whistle", "flute", "harp");

   This should suggest a way of adding elements to an array. A neater way
   of adding elements is to use the statement

push(@food, "eggs");

   which pushes eggs onto the end of the array @food. To push two or more
   items onto the array use one of the following forms:

push(@food, "eggs", "lard");
push(@food, ("eggs", "lard"));
push(@food, @morefood);

   The push function returns the length of the new list.

   To remove the last item from a list and return it use the pop
   function. From our original list the pop function returns eels and
   @food now has two elements:

$grub = pop(@food);     # Now $grub = "eels"


   It is also possible to assign an array to a scalar variable. As usual
   context is important. The line

$f = @food;

   assigns the length of @food, but

$f = "@food";

   turns the list into a string with a space between each element. This
   space can be replaced by any other string by changing the value of the
   special $" variable. This variable is just one of Perl's many special
   variables, most of which have odd names.

   Arrays can also be used to make multiple assignments to scalar
   variables:

($a, $b) = ($c, $d);            # Same as $a=$c; $b=$d;
($a, $b) = @food;               # $a and $b are the first two
                                # items of @food.
($a, @somefood) = @food;        # $a is the first item of @food
                                # @somefood is a list of the
                                # others.
(@somefood, $a) = @food;        # @somefood is @food and
                                # $a is undefined.

   The last assignment occurs because arrays are greedy, and @somefood
   will swallow up as much of @food as it can. Therefore that form is
   best avoided.

   Finally, you may want to find the index of the last element of a list.
   To do this for the @food array use the expression

$#food


<ul><h2><a name=13>Displaying arrays</a></h2></ul>

   Since context is important, it shouldn't be too surprising that the
   following all produce different results:

print @food;    # By itself
print "@food";  # Embedded in double quotes
print @food.""; # In a scalar context


<ul><h2><a name=14>Exercise</a></h2></ul>

   Try out each of the above three print statements to see what they do.


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