From: Daniel Schierbeck <daniel.schierbeck@...>
Date: 2007-02-20T02:45:27+09:00
Subject: Re: For loops don't count down

On Mon, 2007-02-19 at 22:38 +0900, Yukihiro Matsumoto wrote:
> Hi,
> 
> In message "Re: For loops don't count down"
>     on Mon, 19 Feb 2007 22:27:02 +0900, SonOfLilit <sonoflilit@gmail.com> writes:
> 
> |Numeric#step counts down:
> |
> |5.step(-1) do |i|
> | #stuff
> |end
> 
> 5.downto(1) do |i|
> end

Is there a necessity for a range such as 5..0 to be empty? It would
otherwise be easy to make iteration work for such cases. This is a
simplified solution that doesn't take into account #exclude_end?

  class Range
    def each
      obj = first
      if first <= last
        while obj <= last
          yield obj
          obj = obj.succ
        end
      else
        while first >= last
          yield obj
          obj = obj.pre
        end
      end
    end
  end

This would of course require that the objects in such a "reverse" range
respond to #pre, or whatever other name would be more suitable.

I'm basically asking if there is a reason why we shouldn't expand the
functionality of Range#each, other than backwards compatibility (not
that that isn't a big consideration.)


Cheers,
Daniel Schierbeck