Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2005
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2005

[Date Index] [Thread Index] [Author Index]

Search the Archive

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

  • To: mathgroup at smc.vnet.net
  • Subject: [mg54342] Re: [mg54300] Re: [mg54271] Re: Bug Report - Two numerical values for a same variable
  • From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
  • Date: Sat, 19 Feb 2005 02:31:42 -0500 (EST)
  • References: <00ed01c512b0$2f242850$6400a8c0@Main> <curpbn$r28$1@smc.vnet.net> <200502150438.XAA29728@smc.vnet.net> <200502161936.OAA19223@smc.vnet.net> <d3d3aacf7f18939828890ce85676bd26@mimuw.edu.pl> <opsmcn3rqciz9bcq@monster>
  • Sender: owner-wri-mathgroup at wolfram.com

On 17 Feb 2005, at 17:29, DrBob wrote:

> Your "structure" argument is too vague to be useful.

Whether useful or not it is true.


> NumericQ[Pi + E*I]
> NumericQ[Complex[Pi, E]]
> True
> False
>
> The last result, at least, seems unambiguously wrong.


It is not only right but it is the only sensible possibility.
In Mathematica Complex[a,b] when a and b are numeric quantities, such 
as Pi or E or others is not numeric but meaningless. It has to be 
meaningless because Complex[a,b] where a and b are non real is 
meaningless. However, if a and b are numeric but not numbers 
Mathematica would have to use FullSimplify or high precision arithmetic 
to determine if they are real or have non zero imaginary parts (and it 
may not be able to do so anyway).
So until it was determined that a and b have zero imaginary parts 
Complex[a,b] would have to be like the Schroedinger cat that is neither 
dead nor alive: neither meaningful nor meaningless. That's is 
definitely not the way to make a computer algebra program work. So 
Complex[Pi,E] (unlike Pi+ I E to which it is not equal

In[24]:=
Complex[Pi, E] == Pi + I*E

Out[24]=
Complex[Pi, E] == I*E + Pi )

is meaningless. Hence it is not numeric and it is you and not 
Mathematica that is "unambiguously wrong".

Andrzej Kozlowski


  • Prev by Date: Leading Zeros? (question rephrased)
  • Next by Date: Re: "teach" mathematica an integral
  • Previous by thread: Re: Re: Re: Bug Report - Two numerical values for a same variable
  • Next by thread: Re: Re: Re: Bug Report - Two numerical values for a same variable