[sf-perl] Happy fun sorting problem

[Bill Moseley]

On Fri, Jun 10, 2005 at 09:36:51AM -0700, Josh Berkus wrote:
> Folks,
> 
> I can think of a few ways to solve this issue, but none that are elegant.  I'm 
> looking for elegant.
> 
> I have a 3-level heirarchy:
> 
> Category
> 	Sub Category
> 		Item = Value
> 
> I want to print output that formats like:
> 
> Category-1
> 	Sub Category-H
> 		Item_a = Value
> 		Item_f = Value
> 	Sub Category-S
> 		Item_d = Value
> Category-2
> 	Sub Category-B
> 		Item_k = Value
> ...etc...

here's some very old code I used in a project once.  It builds a single string sort key
for fast sorting.  Not sure what all the hash lookups are, but you can
use your imagination.  I think I'm missing some bounds checking,
too...

        for my $sortby ( @sortby ) {

            my $reverse = $sortby eq lc $sortby;
            my $key;
            my $numeric;



            for ( lc $sortby ) {

                # General text
                if ( $strings{$_} ) {
                    $key = lc $student->{ $strings{$_} };
                    last;
                }

                /date/ && do {
                    $key = $student->{S_UNIX_REGISTER_TIME} || 0;
                    $numeric++;
                    last;
                };

                /status/ && do {
                    $key = $status_sort[$student->{S_STATUS_CODE}];
                    $numeric++;
                    last;
                };

                # here's the default

                $key = lc "$student->{LAST_NAME}$student->{FIRST_NAME}";

            }

            if ( $numeric ) {
                $key = $key ^ ( 1 << 31 );  # bias to unsigned
                $sort_key .= pack 'N', $reverse
                                   ? $key ^ 0xffffffff
                                   : $key;
            } else {
                $key ^= "\xFF" x 150 if $reverse;
                $sort_key .= "$key\0";
            }
        }

        $sort_hash{$student} = $sort_key;
    }

    return [ sort { $sort_hash{$a} cmp $sort_hash{$b} } @{$students} ];
}


-- 
Bill Moseley
moseley at hank.org