From: David Garamond <lists@...6.isreserved.com>
Date: 2004-03-03T19:42:35+09:00
Subject: Re: why are Hashes so unsorted? what's your solution?

Ruby Baby wrote:
> I use MySQL databases a lot.  Let's say I have a query to find the
> top-selling albums in my store:
> 
> SELECT sku, artistname, albumtitle, sold FROM albums
> ORDER BY sold DESC LIMIT 20;
> 
> When I get the hash of results from the database, I'm used to making
> the "sku" the hash key since it's the only unique identifier.
> A perfect hash key.  Used everywhere by my iteration methods.
> 
> In PHP, this is no problem.  I get the hash, and I can do the 
> "each" iteration on it, and get my top-selling albums in order.
> 
> In Ruby, it's an unordered jumble.
 > Why is that?

Most language don't guarantee insert order for hash, in fact IIRC some 
deliberately randomize it. It's faster and in some cases needed for 
security reasons. So I guess PHP is the minority here (plus I still hate 
the fact that they merge the concept of array and hash, WTF with that?)

> And what do you think is the Ruby way solution for what I need to do?

  records = {
    "sku1" => ["artist1","title1",100],
    "sku2" => ["artist2","title2",200],
    "sku3" => ["artist3","title3",300],
    "sku4" => ["artist4","title4",400],
    "sku5" => ["artist5","title5",500],
  }
  records.keys.sort.each {|k|
    record = records[k]
    # do stuff with record...
  }

Or you can make a Hash that maintains insert order. I think there is one 
at RAA (http://www.ruby-lang.org/en/raa.html).

-- 
dave