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[B]Perl sort quick question[/B]

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# 1  
Old 10-09-2008
[B]Perl sort quick question[/B]
I've done a quick Google about this, but could not find the answer I want.

Say, there is an array like this:
@A = qw(cd1 a1 ef a2 hij a12 b2 b4 b22);

I want to sort the array in the first order:
@sorted = qw(a1 a12 a2 b2 b22 b4 cd1 ef hij);

And second order:
@sorted = qw(a1 a2 a12 b2 b4 b22 cd1 ef hij);

Is there a way to do this in Perl without using modules?

Thanks a lot!
Last edited by zx1106; 10-09-2008 at 01:44 PM..
# 2  
Old 10-09-2008
Do you consider the sort function a module?
Code:
@sorted=sort(@A);

# 3  
Old 10-09-2008
Thanks! It works for the first order.
# 4  
Old 10-09-2008
What about the second order:
qw(a1 a2 a12 b2 b4 b22 cd1 ef hij);
Thanks!
# 5  
Old 10-09-2008
Yes, you can sort with a custom rule. But what exactly is the rule for the sort? If you cannot work out a formal specification of the sort, no one will be able to do it "correctly".

The following gives the same ordering as you mentioned, but there is no guarantee that it is going to give you the "correct" ordering (as you might expect) for other input values:

Code:
use Data::Dumper;

@A = qw(cd1 a1 ef a2 hij a12 b2 b4 b22);
print Dumper([sort {
	my ($_a, $_b);
	for ([$a, \$_a], [$b, \$_b]) {
		$_->[0] =~ /^(.+?)(\d*)$/;
		${$_->[1]} = [$1, $2];
	}
	($$_a[0] cmp $$_b[0]) || ($$_a[1] <=> $$_b[1]);
} @A]);

# 6  
Old 10-10-2008
Second order which appears to be first sort by alpha then digit:

Code:
my @A = qw(cd1 a1 ef a2 hij a12 b2 b4 b22);

my @sorted = map{$_->[2]}
          sort{$a->[0] cmp $b->[0] || $a->[1] <=> $b->[1]}
          map{/([a-z]*)(\d*)/;[$1,$2,$_]} @A;

print "$_\n" for @sorted;

Google "Schwartzian Transform" if interested in the cached key sort technique.
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