Lists

Tom Kelliher, CS29

Mar. 6, 1997

List or array:

An ordered list of scalar data. Each element of the list is a separate scalar variable with an independent scalar value. Each element has an index associated with it --- its position within the list. The first element of the list has index 0. If a list has n elements, the last element has index n - 1. A list may have any number of elements.

Examples of lists:

@list1 = ("Dee", "Andy", "Mary");
@list2 = (6, 4, 8, 13);

print "$list1[0]\n";
print "$list2[2]\n";

print "$#list1\n";

@list1 = ();

print "$#list1\n";

$i = 0;
while ($i <= $#list2)
{
    print "$list2[$i]\n";
    $i = $i + 1;
}

Example program to read a list of lines from the keyboard, and print them in reverse order:

#!/usr/contrib/bin/perl -w

$input = <STDIN>;
$i = 0;
while ($input)
{
   $inputs[$i] = $input;
   $i = $i + 1;
   $input = <STDIN>;
}

$i = $#inputs;
while ($i >= 0)
{
   print "$inputs[$i]";
   $i = $i - 1;
}

exit 0;