From: Daniel Finnie <dan@...>
Date: 2008-04-07T09:26:17+09:00
Subject: Re: Arbitrary mathematical relations, not just hashes

type.find {|k,v| v == "red"} (will find one match)
type.find_all {|k,v| v == "red"} (will find all matchs)

Alternately, type.invert['red'] (will find one match)

Dan

On Sun, Apr 6, 2008 at 7:52 PM, Kelly Jones <kelly.terry.jones@gmail.com> 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?
>
>  Is there a language that handles mathematical relations naturally/natively?
>
>  I realize SQL does all this and more, but that seems like overkill for
>  something this simple?
>
>  --
>  We're just a Bunch Of Regular Guys, a collective group that's trying
>  to understand and assimilate technology. We feel that resistance to
>  new ideas and technology is unwise and ultimately futile.
>
>