check the difference between 2 arrays

[amlife]

Hello

Thanks everyone for the help earlier, what I would like to learn now is how can I achieve the following :

array1 = (1234567,7665456,998889,000909)
array2 = (1234567,5581445,998889,000909)

Result

5581445 doesn't exist on array1

Thank you

[Roxoff]

There are several ways you could do this.

There's you could iterate over the first array, searching the second array for each entry in the first, then repeat with the arrays swapped.

A second way, which would be more memory intensive but probably much quicker for large arrays would be to sort them both (or a copy of both) then iterate over them both together comparing elements, from each, listing the lower value of the two in each comparison then incrementing the index in that array only. If you find a match then increment both. When one array runs out of elements you list all the elements in the array with elements left.

[drl]

Hi.

Much of the heavy lifting can be done with module List::Compare:

#!/usr/bin/env perl

# @(#) p1	Demonstrate module List::Compare.

use strict;
use warnings;
use List::Compare;

my (@array1) = qw(1234567 7665456 998889 000909);
my (@array2) = qw(1234567 5581445 998889 000909);

# Print arrays.
print " array 1 = \"@array1\"\n";
print " array 2 = \"@array2\"\n";
print "\n";

# Create comparison object.
my ($lc) = List::Compare->new( \@array1, \@array2 );
my ( @lonly, @ronly );

# Calculate differences, left and right.
@lonly = $lc->get_unique;
print " 1,2 = \"@lonly\"\n";

@ronly = $lc->get_complement;
print " 2,1 = \"@ronly\"\n";

exit(0);

producing:

% ./p1
 array 1 = "1234567 7665456 998889 000909"
 array 2 = "1234567 5581445 998889 000909"

 1,2 = "7665456"
 2,1 = "5581445"

The context for me is:

OS, ker|rel, machine: Linux, 2.6.26-2-amd64, x86_64
Distribution        : Debian GNU/Linux 5.0.8 (lenny) 
perl 5.10.0
0.37	List::Compare

In Debian, code often is installed with apt-get. In this case, the package name is liblist-compare-perl, found with apt-cache search compare | grep perl. After that, one can use perldoc List::Compare to see the documentation:

List::Compare(3)      User Contributed Perl Documentation     List::Compare(3)

NAME
       List::Compare - Compare elements of two or more lists
...

Best wishes ... cheers, drl