Re: How to sort hash tables alpha-numeric

Here's a solution using the so-called Schwartzian transform for sorting the keys (the leading "C" is stripped off, and the the key list is sorted by the number before the dash, and then by the number after the dash:

#!/usr/bin/perl

use warnings;
use strict;

my %keys;

$keys{'C10'}->{'C10-1'}=1;
$keys{'C10'}->{'C10-2'}=1;
$keys{'C10'}->{'C10-20'}=1;
$keys{'C10'}->{'C10-3'}=1;

$keys{'C200'}->{'C200-1'}=1;
$keys{'C200'}->{'C200-20'}=1;
$keys{'C200'}->{'C200-3'}=1;
$keys{'C200'}->{'C200-21'}=1;

$keys{'C30'}->{'C30-1'}=1;
$keys{'C30'}->{'C30-2'}=1;
$keys{'C30'}->{'C30-30'}=1;
$keys{'C30'}->{'C30-4'}=1; 

sub sorted { 
    return map { $_->[0] }
        sort { 
            $a->[1] <=> $b->[1] ||
            $a->[2] <=> $b->[2]
        } map { [ $_, split("-", substr($_,1)) ] } @_;
}

foreach my $key (sorted(keys %keys)) {
    print "'$key' => ", $keys{$key}, "\n";
    foreach my $subkey (sorted(keys %{$keys{$key}})) {
        print "   '$subkey' => $keys{$key}->{$subkey}\n";
    }
}
[download]

Arjen

Comment on Re: How to sort hash tables alpha-numeric Download Code

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Re: Re: How to sort hash tables alpha-numeric by juo (Curate) on Oct 19, 2003 at 02:31 UTC
This works perfect although I don't understand yet 100% how the Schwartzian transform works. Their is one small problem that I have with the code is that it should look for all leading characters to be split because now it substr only one but it could be more. (CR30-1 for example) So I tried to modify the code but no success. `sub sorted { return map { $_->[0] } sort { $a->[1] <=> $b->[1] \|\| $a->[2] <=> $b->[2] } map { [ $_, split("-", s/^[A-Z]+//) ] } @_; } foreach my $key (sorted(keys %keys)) { print "'$key' => ", $keys{$key}, "\n"; foreach my $subkey (sorted(keys %{$keys{$key}})) { print " '$subkey' => $keys{$key}->{$subkey}\n"; } }` [download]	[reply] [d/l]
Re: Re: Re: How to sort hash tables alpha-numeric by Aragorn (Curate) on Oct 19, 2003 at 10:46 UTC
The Schwartzian Transform is explained here by the person after who this sorting technique is named. A modified version of the `sorted` routine which also takes the leading letters into account: `sub sorted { return map { $_->[0] } sort { $a->[1] cmp $b->[1] \|\| $a->[2] <=> $b->[2] \|\| $a->[3] <=> $b->[3] } map { [ $_, (/([A-Z]+)(\d+)(?:-(\d+)){1,2}/) ] } @_; }` [download] The `split` function is replaced by a regex which returns a list of letters and the numbers. Arjen	[reply] [d/l] [select]