From: Xavier Noria <fxn@...>
Date: 2007-11-19T10:23:05+09:00
Subject: Re: Open-ended ranges?

On Nov 19, 2007, at 1:50 AM, Clifford Heath wrote:

> What I really want is to be able to define ranges like (1..nil),  
> which is an
> open-ended range starting from 1. Of course this doesn't work, but  
> not for the
> reason I expected. There seems to be some magic inside MRI that  
> prevents it.
>
> Like if I define:
>
> class End
> 	attr_reader :e
> 	def initialize(e)
> 		@e = e
> 	end
> 	def <=>(other)
> 		@e <=> other.e
> 	end
> 	def succ
> 		@e && @e.succ
> 	end

Note that #succ is expected to return an instance of End. In  
particular End.new(nil).succ should return some End instance.

I'd expect as well x < x.succ for all x in End and if you add that  
condition you end up putting something at the end of the positive  
integers, and adding its successors. As if you put a copy of N after  
N. That's one of the examples we talked about some weeks ago:

   http://advogato.org/person/fxn/diary/473.html

-- fxn