PHP array_unique in Perl
Well this function is very handy when you are working with flatfiles, or for example you dont have a category table on your mysql database, so entries have repeatead categories.
What the function array_unique does, is return an array without the repeated elements given in the array you gave as argument.
For example:
<?php
$array = array(1,2,1,3,4,1,2,6,4,5,1);
$array = array_unique($array);
sort($array);
print_r($array);
?>
That will print
Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4 [4] => 5 [5] => 6 )
It deletted repeated elements, now, how to do that in perl?
Well that function does not exists in perl, anyways, you can create it, its not very hard… Here are some examples, this is the one i made
sub array_unique
{
my @list = @_;
my %finalList;
foreach(@list)
{
$finalList{$_} = 1; # delete double values
}
return (keys(%finalList));
}
It works exactly the same as PHP’s array_unique, someone at Cafe PM also suggested this one, which is shorter but to be honest i dont understand it much
sub array_unique
{
my %seen = ();
@_ = grep { ! $seen{ $_ }++ } @_;
}
That function also works the same as the one before, and the code in perl would be
#!/usr/bin/perl
use CGI’:all’;
use strict;# Code…
sub array_unique
{
my %seen = ();
@_ = grep { ! $seen{ $_ }++ } @_;
}
# More code….my @array = (1,2,1,3,4,1,2,6,4,5,1);
@array = sort(array_unique(@array));
print header, “@array”;
And that will print
1 2 3 4 5 6
Well, thats it, enjoy!
on September 6, 2008 on 12:35 am
b => sub array_unique
{
my @list = @_;
my %finalList;
foreach(@list)
{
$finalList{$_} = 1; # delete double values
}
return (keys(%finalList));
}
it is executed quicker than:
a => sub array_unique
{
my %seen = ();
@_ = grep { ! $seen{ $_ }++ } @_;
}
Rate b a
b 11737/s — -23%
a 15299/s 30% —
b best algorithm 🙂
on April 15, 2009 on 6:22 pm
Nice 😀 i didnt benchmark hehe
on April 8, 2012 on 11:07 am
Burg but it breaks array order = bad.
on June 7, 2012 on 7:18 am
Why do we have to create a new array @finalList ? Can’t we just delete values in the initial array @lines ?