From: MonkeeSage <MonkeeSage@...>
Date: 2007-11-25T01:50:00+09:00
Subject: Re: Hashes, Sets, and eql?

On Nov 24, 8:34 am, Phrogz <phr...@mac.com> wrote:
> Not always true:
>
> [...]

Point taken. But still should not be relied on.

> This discussion (using Hashes as hash or set keys, and the
> requirements and possible implementations of of eql? for this to work
> as sometimes desired) occurred in the last month or two on this list.

Thanks, found it. [ http://groups.google.com/group/comp.lang.ruby/browse_thread/thread/572e8d8b01a7d24e/c5f532d868afab05
].

So it seems the only way to do it is something like...

class Set
  def hash
    to_a.sort.hash
  end
  def eql?(o)
    return false unless o.is_a?(Set)
    @hash == o.instance_eval{@hash}
  end
end

...which is basically what Aaron was already doing.

Seems like there really should be a way to index keys on value rather
than identity (even if it's not the default or requires a separate
class like someone on the other thread mentioned that Smalltalk has).

Regards,
Jordan