NAME

Array::Unique - Arrays that allow only unique values

SYNOPSIS

use Array::Unique;
tie @a, Array::Unique;

Use @a as a regular arrray.

DESCRIPTION

There is not much to say here.
The module provides you with a tie-able array
that allows only unique values.
It does not allow undef as a value in the array.

DISCUSSION

When you are collecting a list of items and you want 
to make sure there is only one occurence of each item,
you have several option:

1) using hash

Some people use the keys of a hash to keep the items and
put an arbitrary value as the values of the hash:

To build such a list:
%unique = map { $_ => 1 } qw( one two one two three four! );

To print it:
print join ", ", sort keys %unique;

To add values to it:
%unique = map { $_ => 1 }
       (keys %unique, qw( one after the nine oh nine ));

To remove values:
delete @unique{ qw(oh nine) };

To check if a value is there:
$unique{ $value };        # which is why I like to use "1" as my value

(thanks to Gaal Yahas for the above explanation)

There are three drawbacks I see:
1) You type more.
2) Your reader might not understand at first why did you use hash 
   and what will be the values.
3) You lose the order.

Usually non of them is critical but when I saw this the 10th time
in a code I had to understand with 0 documentation I got frustrated.

2) using array

Other people might use real arrays and on each update or
before they want to use the uniqueness feature of the array
they might run a function they call @a = unique_value(@);

This is also good but you have to implement the unique_value
function AND you have to make sure you don't forget to call it.
Something I have a tendency to do just before code release.

3) using Array::Unique

So I decided to write this module because I got frustrated
by my lack of understanding what's going on in that code
I mentioned.
In addition I thought it can a good game to write this and
then benchmark it.
Additionally it is nice to have your name displayed in 
bright lights all over CPAN ... or at least in a module.

Array::Unique lets you tie an array to hmmm, itself (?)
and makes sure the values of the array are always unique.

TODO

Benchmark speed

Add faster functions that don't check uniqueness so if I 
  know part of the data that comes from a uniques source then
  I can speed up the process,
  In short shoot myself in the leg.

Enable optional compare with other functions

Setup other implementations

AUTHOR

Gabor Szabo <gabor@perl.org.il>

COPYRIGHT AND LICENCE

Copyright (C) 2002 Gabor Szabo <gabor@perl.org.il>
All rights reserved.


You may distribute under the terms of either the GNU 
General Public License or the Artistic License, as 
specified in the Perl README file.

No WARRANTY whatsoever.