How to make an array from an array?

[Anonymous Monk]

Hi. I have array @all_names=(john, andy, bill,andy, john, julia, bill). What I'd like to do is make an other array based on the first array. Array called @names should have every name just one time: (john,andy,bill, julia)
Pasi

[barrd]

Straight from Perl Cookbook (well almost :-)

my @all_names = qw/john andy bill andy john julia bill/;
my %seen = ();
my @names = grep { ! $seen{$_} ++ } @all_names;
print join(' ', @names);

This prints john andy bill julia, I'm sure you'll get other variations.

Update 1: Fixed typos in code D'oh.

Update 2: As TomDLux rightly pointed out, you may wish to sort the names alphabetically, if so just change line 3 to this:

my @names = sort grep { ! $seen{$_} ++ } @all_names;

Returning: andy bill john julia (which is what I meant to do originally but ... err... didn't)

[TomDLux]

This is a frequently asked question, the Search window will find the answer for you.

• If order doesn't matter, use the values as keys to a hash, then extract a list of the keys.
• If order does matter, go through the list, copying elements which have not been seen yet. As each element is copied, mark it as seen by setting a hash element.
• go through the original array, checking whether an element has been seen yet, unsplice-ing duplicates.

Good luck with your homework.

[Anonymous Monk]

So you're looking to eliminate duplicates?

perldoc -q duplicate
Found in C:\Perl\lib\pod\perlfaq4.pod
  How can I remove duplicate elements from a list or array?

:)

[etcshadow]

@unique_list = keys %{{map{($_=>1)} @non_unique_list}};

[Anonymous Monk]

Thank you all for bothering to answer. You have solved my problem.
As you might have noticed :) english is not my native lanquage. So it's sometimes difficult to make searches because of not knowing the right expressions or words for something.
Pasi