http://www.perlmonks.org?node_id=398021


in reply to intermix list of items

btw, the compare function is suppose to return -1, 0, +1, not just 0 and 1, so I expect your sort has some amount of randomness to it.

Maybe you want something like:

sub intermix { my $a_prime = join('.', reverse(split(/\./, $a))); my $b_prime = join('.', reverse(split(/\./, $b))); $a_prime cmp $b_prime } my @list = ('10.1.1.1', '10.1.1.2', '10.2.2.1', '10.2.2.2'); @list = sort intermix @list; use Data::Dumper; print Dumper(@list); __END__ output ====== $VAR1 = '10.1.1.1'; $VAR2 = '10.2.2.1'; $VAR3 = '10.1.1.2'; $VAR4 = '10.2.2.2';

Almost the same, but more efficient:

sub intermix { my $a_prime = reverse($a); my $b_prime = reverse($b); $a_prime cmp $b_prime } my @list = ('10.1.1.1', '10.1.1.2', '10.2.2.1', '10.2.2.2'); @list = sort intermix @list; use Data::Dumper; print Dumper(@list); __END__ output ====== $VAR1 = '10.1.1.1'; $VAR2 = '10.2.2.1'; $VAR3 = '10.1.1.2'; $VAR4 = '10.2.2.2';

This is the same thing as the last, but probably more efficient, especially for longer lists:

my @list = ('10.1.1.1', '10.1.1.2', '10.2.2.1', '10.2.2.2'); @list = map { $_->[0] } sort { $a->[1] cmp $b->[1] } map { [ $_, ''.reverse($_) ] } @list; use Data::Dumper; print Dumper(@list); __END__ output ====== $VAR1 = '10.1.1.1'; $VAR2 = '10.2.2.1'; $VAR3 = '10.1.1.2'; $VAR4 = '10.2.2.2';

Note: Given addresses of the form 'a.b.c.d', the above snippets only work well if there is there is a common 'd' of for every 'a.b.c' in the list.