From: why the lucky stiff <ruby-talk@...>
Date: 2004-05-21T05:34:08+09:00
Subject: Re: Overriding "", [], and {}

Bill Atkins wrote:

>Is there any way to cause "", [], and {} to have different behaviors. 
>I'd like to be able to have {} create OrderedHash's instead of Hash's,
>but I don't know how to change this behavior.  If I do Hash =
>OrderedHash, then Hash.new will create an OrderedHash, but {} still
>gives me an old-fashioned hash.
>  
>
This isn't what you're looking for, but I think it's the best answer.  
Both Array and Hash have a builtin [] class method, which can be used to 
define new Arrays or Hashes.

  >> a = Array['goats', 'coats', 'asymptotes']
  => ["goats", "coats", "asymptotes"]
  >> h = Hash['g' => 'goats', 'c' => 'coats']
  => {"c"=>"coats", "g"=>"goats"}

You can use the same class method to get away with really clean 
definitions of new Array/Hash derivatives.  For example, YAML has an 
Omap (ordered hash) class:

  >> o = YAML::Omap['c', 'coats', 'g', 'goats']
  => [["c", "coats"], ["g", "goats"]]
  >> o.class
  => YAML::Omap

_why