use strict;
use warnings;
use diagnostics;

sub distance {
    my ($aa, $bb) = @_;
    return sqrt(($aa->[0] - $bb->[0])**2 +
                ($aa->[1] - $bb->[1])**2 +
                ($aa->[2] - $bb->[2])**2);
}

my $source = "./CONTCAR";

open(IN, '<', $source) or die "Couldn't open $source: $!\n";

my @data = map [ split ], grep /\S/, <IN>;

foreach my $d1 (@data) {
    foreach my $d2 (@data) {
        printf "($d1->[0],$d1->[1],$d1->[2]) <-> ($d2->[0],$d2->[1],$d
+2->[2]) = %f\n", distance($d1, $d2);
    }
}

close IN;

print "Done.\n";
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That's so beautiful. Thank you. It is greatly appreciated. I understand the foreach loop a lot better with an example, thanks.

jcklasseter:

Yeah, just get rid of the -$* part. Normally, you'd compute the distance like:

return sqrt( ($x2 - $x1)**2 + ($y2 - $y1)**2 + ($z2 - $z1)**2 );
[download]

But another way to think of it would be:

my $dx = $x2 - $x1;
my $dy = $y2 - $y1;
my $dz = $z2 - $z1;

return sqrt( $dx**2 + $dy**2 + $dz**2 );
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Your map statement is computing dx, dy and dz (you've just labelled them as x, y and z), so after your map statement, you can just use:

return sqrt( $x**2 + $y**2 + $z**2 );
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Though I'd suggest renaming the variables x, y and z to clarify the code.

...roboticus

When your only tool is a hammer, all problems look like your thumb.

I get the 'Subract X from itself and get 0' part. But what I don't get is how to fix the code to have it do what I want; I.E x2-x1 iteratively.