From: Mike Fletcher <lemurific+rforum@...>
Date: 2006-08-04T00:21:12+09:00
Subject: Re: A left-exclusive Range class

Brian Guthrie wrote:
> Cyrus Hall wrote:
>> have been a related debate about this on ruby-talk back in Oct. 2004,
>> with the conclusion being, to paraphrase the entire discussion, "this is
>> hard, lets forget about it for now." 
>> 
>> Has this been discussed since 2004?  Would people be interested in
>> finding a way to get left-exclusion into the Range class?  This may be
>> something that has been addressed in all the language work going into
>> 1.9/2.0, and if so, any pointers would be greatly appreciated.

Doesn't preserve the fact that it started as a left exclusive range, but 
how about:

class Range
  alias :orig_initialize :initialize
  def initialize( s, e, exclusive=false )
    case exclusive
    when false, true
      orig_initialize( s, e, exclusive )
    when :left
      orig_initialize( s.succ, e )
    when :right
      orig_initialize( s, e, true )
    when :both
      orig_initialize( s.succ, e, true )
    end
  end
end

Then you can do Range.new( 1, 5, :left ) or Range.new( 1, 5, :right ) or 
use the .. / ... operators as well.

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