#!/usr/bin/perl -w
#
# rev-sort -- <tkil@scrye.com> 1999-04-19
#
# inspired by a question on #perl, this program sorts a list of "file
# revisions".
#

use strict;

sub rev_sort
{
  # split up the keys on ".":
  my @ar = split /\./, $a;
  my @br = split /\./, $b;
  
  # these need to be in the outer scope, since we're going to
  # compare them after we leave the "for" loop
  my ($xa, $xb) = (0, 0);
  
  # loop while we still have values, and while the current values
  # are still equal.
  while (@ar && @br && $xa == $xb)
  {
    # get the appropriate values from each array
    $xa = @ar ? shift @ar : -1;
    $xb = @br ? shift @br : -1;
  }
  
  # since these were the first unequal ones (or, if they're
  # identical, we ran off the end of the loop), the comparison
  # between these two is the appropriate one.
  $xa <=> $xb || @ar <=> @br;
}

# read in sample data
my @test = <DATA>;
chomp @test;

$" = ", "; # man perlvar ... put a comma when we expand arrays in
           # strings.

print "before: [@test]\n";
my @sorted = sort rev_sort @test;
print "after: [@sorted]\n";

exit;

__END__
1.0
1.1
6.12
10.4
10.0.3
1.1.1
1.1.2
2.3
1.3
1.4
3.1
3.2
4.5
1.5
1.5.0
1.5.2