From: Brian Guthrie <bguthrie@...>
Date: 2006-08-03T23:56:12+09:00
Subject: Re: A left-exclusive Range class

Cyrus Hall wrote:
> The current Range class in ruby is quite useful, however, I was recently
> trying to capture a simple algorithm and ended up needing to express
> left-exclusion.  This is the one feature ruby currently does not support
> in its Range class.
> 
> I did some digging into 1.8.4's Range implementation and it appears
> that the changes needed to support left-exclusion would be minimal.
> Rather, the problem seems syntactical.  Currently '..' and '...' are
> used to represent right-inclusion and -exclusion, respectively.  This
> syntax clearly can not be extended to left-exclusion.  There appears to
> 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.
> 
> Ciao,
> Cyrus Hall

You could try just appropriating a different piece of syntax and using 
it for your own evil purposes, e.g. <<

class Fixnum
   def <<(number)
     (self + 1)..number
   end
end

for i in 1<<10
   # i starts at 2
end

Brian Guthrie