Perl: More on Lists and Hashes

Just as a refresher, in our previous article we went into detail about just what exactly a two-dimensional list was, how to print a single record from them and how to print an entire row. We also explained how to create variables, lists, and hashes using a two-dimensional array.

Setting Up the “Database”

I like to throw around that word two-dimensional. You'll find it runs rampant throughout this article (and the last one). It's a big word that soothes my little mind. So try not to get too annoyed as you see it thrown carelessly about.

For starters, let's create a two-dimensional list for a book collection. Much to the chagrin of my girlfriend I have about nine billion books and nowhere to put them. So with this article I will try to appease her by adding some to a database. Here are the fields of data that will appear in our “database”:

• Book Number

• Author

• Title

• Genre

• Number of Stars (how good the book was in a ranking of 1-5, with five being the best)

• Which shelf on the bookshelf it is located

Here is the code to create the list and print it out to make sure everything is correct:

#!/usr/bin/perl

@Bookshelf = (

[" # ", " Author ", " Title ", " Genre "," Rating "," Location " ],

[' 1 ', ' Stephen King ', ' It ', ' Horror ', ' 5 ', ' Top '],

[' 2 ', ' Clive Barker ', ' Imajica ', ' Horror ', ' 5 ', ' Top '],

[' 3 ', ' Neil Gaiman ', ' American Gods ', ' Dark Fantasy ',' 5 ',

' Top '],

[' 4 ', ' Dean Koontz ', ' Tick-Tock ', ' Horror ', ' 1 ', '

GarbageCan '],

[' 5 ', ' Charles Bukowski ', ' Letters from a Dirty Old Man ', '

Literature ', ' 5 ', ' Top '],

[' 6 ', ' Chuck Pahluniak ', ' Fight Club ', ' Dark Fantasy ', ' 5 ', ' Middle ']

);

print "\n\n";

print @{@Bookshelf[0]};

print "\n";

print @{@Bookshelf[1]};

print "\n";

print @{@Bookshelf[2]};

print "\n";

print @{@Bookshelf[3]};

print "\n";

print @{@Bookshelf[4]};

print "\n";

print @{@Bookshelf[5]};

print "\n";

print @{@Bookshelf[6]};

print "\n";

print @{@Bookshelf[7]};

Here, in the above code, we created a fake set of headers to print out, which occupy row 0. When we print this code we get the following result:

  # Author Title Genre Rating Location

  1 Stephen King It Horror 5 Top

  2 Clive Barker Imajica Horror 5 Top

  3 Neil Gaiman American Gods Dark Fantasy 5 Top

  4 Dean Koontz Tick-Tock Horror 1 GarbageCan

  5 Charles Bukowski Letters from a Dirty Old Man Literature 5 Top

  6 Chuck Pahluniak Fight Club Dark Fantasy 5 Middle