From: Robert Dober <robert.dober@...>
Date: 2009-07-23T01:56:10+09:00
Subject: Re: Incorrect -0.0.hash - Ruby bug.

On 7/22/09, John W Higgins <wishdev@gmail.com> wrote:
> Morning Thomas,
>
>
>  On Wed, Jul 22, 2009 at 9:24 AM, Thomas B. <tpreal@gmail.com> wrote:
>
>  > Hello. I just found a bug in Ruby, version 1.9.1p0, Windows.
>  >
>  > In the rdoc to Object#hash we read
>  > (http://ruby-doc.org/core/classes/Object.html#M000337):
>  >
>  > "This function must have the property that a.eql?(b) implies a.hash ==
>  > b.hash."
>  >
My understanding is that this relationship shall be kept for the
purpose of correct hash key behavior

553/60 > ruby -v -e 'p( {0.0 => 42}[-0.0] )'
ruby 1.9.1p243 (2009-07-16 revision 24175) [i686-linux]
nil

which is not nice.
That said floats as hash keys are a bad idea of course because of
equality is not very well defined anyway.

Cheers
Robert

>
>
> Actually Float overrides both #eql? and #hash so the contract is not
>  applicable inside that class. Is that the best option in the world?? -
>  probably not - but that would make it a non bug in theory.
>
>
>  John
>


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