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MathGroup Archive 2005

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Re: Re: Bug Report - Two numerical values for a same variable

  • To: mathgroup at smc.vnet.net
  • Subject: [mg54336] Re: [mg54296] Re: Bug Report - Two numerical values for a same variable
  • From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
  • Date: Thu, 17 Feb 2005 10:30:53 -0500 (EST)
  • References: <cuhr4q$978$1@smc.vnet.net> <cukc65$lup$1@smc.vnet.net> <200502130521.AAA03676@smc.vnet.net> <opsl4914q7iz9bcq@monster> <002301c51217$ad7438b0$b5803e44@Dell> <cup6bc$e11$1@smc.vnet.net> <curp0c$qv3$1@smc.vnet.net> <200502161936.OAA19201@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

On 16 Feb 2005, at 20:36, Maxim wrote:

> On Tue, 15 Feb 2005 03:06:52 +0000 (UTC), Carl K. Woll
> <carlw at u.washington.edu> wrote:
>
>>
>> Objects with head Rational are atoms, so you don't have access to the
>> integers inside a rational object. It's the samething as complex 
>> numbers.
>> For example,
>>
>> Complex[6,7] /. 7->1
>> 6 + 7 I
>>
>> Carl Woll
>>
>
> However, if I construct something like Complex[E, E] manually, it 
> won't be
> an atom, and some functions will have problems with it:
>
> In[1]:=
> Complex[E, E] // Re // N
> Complex[E, E] // Re // ComplexExpand // N
>
> Out[1]=
> 2.7182818
>
> Out[2]=
> 2.7182818 + 2.7182818 I
>
> Perhaps this is an unallowed construct, but how am I supposed to know 
> that
> it's unallowed?
>
> Maxim Rytin
> m.r at inbox.ru
>


Well, you can check that

In[16]:=
Complex[E, E] == E + I*E

Out[16]=
Complex[E, E] == (1 + I)*E

in other words, these two expressions are not considered equal. Even 
more obviously Rational[Pi,Pi] does not return 1.
In general it is certainly true in the case of Mathematica that you 
can't conclude from the fact that there is no explicit statement saying 
that something is not allowed that it will be all right to do it. 
Rather like in real life, I would say.



Andrzej Kozlowski
Chiba, Japan
http://www.akikoz.net/andrzej/index.html
http://www.mimuw.edu.pl/~akoz/


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