From: Gerry Ford <wade@...>
Date: 2008-02-06T10:06:53+09:00
Subject: Re: hash value inconsistencies

Tim Pease wrote:
> On Feb 5, 2008, at 4:04 PM, Clifford Heath wrote:
> 
>>> platforms?  I'd  like to have some method that I could call on an  
>>> object that would  return a reproducible value that would uniquely  
>>> identify that object.
>>
>> That's not possible. There is more entropy in an arbitrary object than
>> can be represented in a FixNum. Basic coding theory stuff. If it was
>> possible, then you could code all the data in all the databases in the
>> world into a single Fixnum :-).
> 
> 
> Darn information theory!  I just need a fixnum. The number of objects
> we are creating is pretty tiny -- maybe 100.
> 
> I was quite surprised that the Ruby "hash" method is not consistent
> across platforms. The solution is to roll my own hash function that
> produces consistent results.  Just wondering about the more general
> questions regarding the built in hash function.
What in particular are you going to hash?  Under what circumstances do 
you want to bomb out?

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