in reply to RFC:A brief tutorial on Perl's native sorting facilities.
When I am doing things with sort I have a standard routine (which I call lexically) that attempts to implement a more natural sort order.
Because of the scoping of $a and $b I have
never made this into a module but normally just copy it into the script
foreach my $foo (sort lexically @list)
{
...
}
...
sub lexically
{
# This routine gives us a sort order that more closely matches
# what a naive use would expect (ie "9z" comes before "10a")
# The simple implementation style makes the code easier
# to follow
my($a_,$b_) = @_;
# If we are called by sort the old @_ gets left around
# attempt to detect this and grab values from $a and $b
if(!defined($a_)  !defined($b_) 
ref($a_)  ref($b_)  $#_ != 1)
{
$a_ = $a;
$b_ = $b;
}
return 0
if($a_ eq "" && $b_ eq "");
return 1
if($a_ eq "");
return 1
if($b_ eq "");
my($a_1,$a_t,$a_2,$b_1,$b_t,$b_2);
if($a_ =~ /^(\d+)/)
{
$a_t = 0; $a_1 = $1; $a_2 = $';
}
elsif($a_ =~ /^(\D+)/)
{
$a_t = 1; $a_1 = $1; $a_2 = $';
}
if($b_ =~ /^(\d+)/)
{
$b_t = 0; $b_1 = $1; $b_2 = $';
}
elsif($b_ =~ /^(\D+)/)
{
$b_t = 1; $b_1 = $1; $b_2 = $';
}
if($a_t == 0 && $b_t == 0)
{
# Both start with a numeric value
return lexically($a_2,$b_2)
if($a_1 == $b_1);
return $a_1 <=> $b_1;
}
if($a_t == 1 && $b_t == 1)
{
# Both start with text, fold everything to
# lower case (so "A" is the same as "a"
# which is what I want, YMMV)
my $r = lc($a_1) cmp lc($b_1);
return lexically($a_2,$b_2)
if($r == 0);
return $r;
}
return 1
if($a_t == 0);
return 1;
}
