Re: RFC:A brief tutorial on Perl's native sorting facilities.

[hawtin]

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 "9-z" comes before "10-a")

    # 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;
  }

[xdg]

I have never made this into a module but normally just copy it into the script

Your post was a great addition to the sorting tutorial. So it pains me to point out Sort::Naturally