From: Andrew Walrond <andrew@...>
Date: 2005-05-05T23:45:24+09:00
Subject: Re: Whats so different about a Hash?

On Thursday 05 May 2005 15:41, Florian Gro� wrote:
> Andrew Walrond wrote:
> > Is Hash#to_a guaranteed to sort the elements? My tests show that it does,
> > but perhaps .to_a.sort might be safer?
>
> I think that two hashes with the same elements will also have the same
> order. This might however not be true anymore in the future. (There were
> talks about retaining insert order.)
>
> So calling .sort might indeed be a good idea.
>
> > So I propose
> >
> >  class Hash
> >   def hash()
> >    [self.to_s.sort,self.class].hash
> >   end
> >   def eql?(other)
> >    self.hash === other.hash
> >   end
> >  end
>
> Be careful about defining eql?() in terms of hash(). hash values will
> and can produce collisions and Ruby will always use eql?() even after
> the hash codes match to check if the elements are indeed the same.
>
> If you implement eql?() in terms of hash() you will however get false
> positives in case of collisions.

What does 1.9 do for Hash#eql?  ?

Andrew