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MathGroup Archive 2005

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Re: Re: Bug in 5.1??

  • To: mathgroup at smc.vnet.net
  • Subject: [mg54489] Re: [mg54448] Re: [mg54349] Bug in 5.1??
  • From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
  • Date: Mon, 21 Feb 2005 03:45:08 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

I never wrote this makes sense. I only pointed out that if you think it 
is a bug you should report it. On the other hand it has been a part of 
Mathematica since the first version I used, which was version 1.2, I 
think. Since then this issue has been discussed almost every year. From 
what has been explained, both on this list and in other places, it is a 
consequence of certain shortcuts that Significance arithmetic makes to 
achieve reasonable speed. It is harmless because nobody ever needs to 
compute anything with two digits of precision.

Andrzej Kozlowski


On 20 Feb 2005, at 17:58, DrBob wrote:

> N[50000,2] should represent something between, say, 49500 and 50500, 
> both of which are positive. If it means something other than that, 
> please enlighten us!!
>
> Meanwhile, perhaps we can use Interval to interpret it:
>
> Interval[N[50000, 2]]//InputForm
> Interval[
>   {49488.`1.9955298983230858,
>    50512.`2.0044245602121236}]
>
> Interval@N[50000,2]>0
> True
>
> So I don't see how this makes sense:
>
> N[50000,2]>0
> False
>
> Bobby
>
> On Sun, 20 Feb 2005 10:53:16 +0100, Andrzej Kozlowski 
> <akoz at mimuw.edu.pl> wrote:
>
>> *This message was transferred with a trial version of CommuniGate(tm) 
>> Pro*
>> Then surely you must have filed a bug report as it would be
>> irresponsible not to!
>>
>> Andrzej Kozlowski
>>
>> On 20 Feb 2005, at 06:10, DrBob wrote:
>>
>>> This behavior will find defenders, I'm sure, but it certainly looks
>>> like a bug to ME.
>>>
>>> Bobby
>>>
>>> On Sat, 19 Feb 2005 02:31:49 -0500 (EST), Gehrmann, James E
>>> <jgehrman at saclink.csus.edu> wrote:
>>>
>>>> I'm running Mathematica v. 5.1 under WinXP and had the following
>>>> interaction with Mathematica:
>>>> 5>0
>>>>
>>>> True
>>>>
>>>> 5.>0
>>>>
>>>> True
>>>>
>>>> N[5]>0
>>>>
>>>> True
>>>>
>>>> N[5,3]>0
>>>>
>>>> True
>>>>
>>>> N[5,2]>0
>>>>
>>>> False
>>>>
>>>> N[50000,2]>0
>>>>
>>>> False
>>>>
>>>> Are the last two results a bug or am I not understanding the N
>>>> function?
>>>>
>>>> Thanks for you help.
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>> --
>>> DrBob at bigfoot.com
>>> www.eclecticdreams.net
>>>
>>>
>>
>>
>>
>>
>
>
>
> -- 
> DrBob at bigfoot.com
> www.eclecticdreams.net
>
>


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