Test For Dupplicate elements in an array

2004-04-20 Thread neill . taylor 
I need to test if an array holds duplicates, and if so do something.

What is the slickest way of doing this ?

Neill



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RE: Test For Dupplicate elements in an array

2004-04-20 Thread Thomas Bätzler 
[EMAIL PROTECTED] asked:
 I need to test if an array holds duplicates, and if so do something. 

Try

use strict;
use warnings;

my @array = qw(foo baz bar foo);
my %have;

foreach my $item (@array){
  warn duplicate item $item if exists $have{$item};
  $have{$item}++;
}

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Re: Test For Dupplicate elements in an array

2004-04-20 Thread Jeff 'japhy' Pinyan 
On Apr 20, [EMAIL PROTECTED] said:

I need to test if an array holds duplicates, and if so do something.

What is the slickest way of doing this ?

The documentation offers a couple ways; the most common idiom uses a hash,
as other people have shown.

However, you can leave the hard work to Perl if you use the
Tie::Array::Unique module, available on CPAN:

  http://search.cpan.org/~pinyan/Tie-Array-Unique-0.01/

Basically, if you do:

  use Tie::Array::Unique;
  tie my(@data), 'Tie::Array::Unique';

and then use @data normally, it will make sure you don't duplicate any
elements.

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RE: Test For Dupplicate elements in an array

2004-04-20 Thread Bob Showalter 
[EMAIL PROTECTED] wrote:
 I need to test if an array holds duplicates, and if so do something.

If you just need to check for the presence of a duplicate, something like
this will do the trick:

  sub has_dup { my %seen; $seen{$_}++  return 1 for @_; }

Of course, all the hash-based methods depend on uniqueness being determined
by the stringified version of the array elements.

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