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MathGroup Archive 2004

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Re: Arbitrary-precision numbers in patterns

  • To: mathgroup at smc.vnet.net
  • Subject: [mg45409] Re: Arbitrary-precision numbers in patterns
  • From: drbob at bigfoot.com (Bobby R. Treat)
  • Date: Tue, 6 Jan 2004 04:17:19 -0500 (EST)
  • References: <btb906$jqd$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

I can't WAIT to hear somebody explain why this is acceptable behavior!!!

Bobby

Maxim <dontsendhere@.> wrote in message news:<btb906$jqd$1 at smc.vnet.net>...
> Compare
> 
> In[1]:=
> Do[ f[k] = k, {k, 1., 17.} ]
> f[1.`20]
> Clear[f]
> 
> Out[2]=
> 1.
> 
> and
> 
> In[1]:=
> Do[ f[k] = k, {k, 1., 18.} ]
> f[1.`20]
> Clear[f]
> 
> Out[2]=
> f[1.0000000000000000000]
> 
> -- and the user's best bet to figure out how it'll work is probably to
> flip a coin.
> 
> The reason is probably just that the hashing mechanism breaks down,
> because the result returned by Mathematica changes after it re-sorts
> some internal table of DownValues for f (the 'boundary value' 17 is for
> version 5.0 on my machine; if 17. and 18. don't work, try 2. and 100.).
> But in general, my opinion is that it is only to be expected -- when we
> don't even know for sure how the definitions for f can be reordered.
> 
> Maxim Rytin
> m.r at prontomail.com


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