On Sun, 2008-04-06 at 16:52 -0700, Kelly Jones wrote:
> Many programming languages (including Perl, Ruby, and PHP) support hashes:
>
> $color['apple'] = 'red';
> $color['ruby'] = 'red';
>
> $type['apple'] = 'fruit';
> $type['ruby'] = 'gem';
>
> This quickly lets me find the color or type of a given item.
>
> In this sense, color() and type() are like mathematical functions.
>
> However, I can't easily find all items whose $color is 'red', nor all
> items whose $type is 'fruit'. In other words, color() and type()
> aren't full mathematical relations.
>
> Of course, I could create the inverse function as I go along:
>
> $inverse_color['red'] = ['apple', 'ruby']; # uglyish, assigning list to value
>
> and there are many other ways to do this, but they all seem kludgey.
>
> Is there a clean way to add 'relation' support to Perl, Ruby, or PHP?
Yes, create a class/object to handle the relationship. That way, the
details are hidden and may be anything you want.
E.g.
use Relationship;
my $color = new Relatinship;
$color->add( 'apple', 'red' );
$color->add( 'ruby', 'red' );
my $type = new Relationship;
$type->add( 'apple', 'fruit' );
$type->add( 'ruby', 'gem' );
my @red_things = $color->find( undef, 'red' );
--
Just my 0.00000002 million dollars worth,
Shawn
99% of you are just big dumb apes!
+------------\
| Shangri La \
| 40,000 KM /
+------------/
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