From: Hugh Sasse <hgs@...>
Date: 2005-09-14T02:45:21+09:00
Subject: Re: Sets, uniqueness not unique.

On Wed, 14 Sep 2005, David A. Black wrote:

> Hi --
>
> On Wed, 14 Sep 2005, Hugh Sasse wrote:
>
>> 
>> Sets *can't* hold duplicates, and include depends on eql? for Sets.
>
> Are you sure about that latter point?  In set.rb:

Yes I was, but it turns out that it was with the certainty that comes
before falling flat on one's face.  I remembered seeing it in the ri
docs, and sure enough, it isn't there!

[What was that fidonet .sig? "Open mouth, insert foot, echo
internationally"? :-)]

>
>  def include?(o)
>    @hash.include?(o)
>  end
>
> and in hash.c:
>
>    if (st_lookup(RHASH(hash)->tbl, key, 0)) {
>        return Qtrue;
>    ... }
>
> I haven't followed the trail beyond that... but I think any two
> student objects will count as different hash keys, even if they have
> similar string data.

Which would explain a lot. Thank you.  Ara's hash function should
fix this for me.
>
>
> David
>
         Thank you,
         Hugh