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Re: Re: When is a List not a List?

• To: mathgroup at smc.vnet.net
• Subject: [mg90997] Re: [mg90956] Re: [mg90947] When is a List not a List?
• From: DrMajorBob <drmajorbob at att.net>
• Date: Sat, 2 Aug 2008 03:27:25 -0400 (EDT)
• References: <200807310656.CAA07700@smc.vnet.net>
• Reply-to: drmajorbob at longhorns.com

"the world is full of functions with parameters that can be evaluated  
pointwise (once numeric parameters have been substituted) but cannot be  
evaluated [properly] by Evaluate"

Ah! I see your point, and a good point it is.

Bobby

On Fri, 01 Aug 2008 15:44:12 -0500, Andrzej Kozlowski <akoz at mimuw.edu.pl>  
wrote:

> On 1 Aug 2008, at 21:18, DrMajorBob wrote:>
>> In light of all that, in what way have the rest of us failed to  
>> understand "a bit of mathematics"?
>
> Te bit of mathematics (and computer algebra) you clearly do not  
> understand is the very basic fact when you solve many kinds of algebraic  
> equations with symbolic parameters you inevitably introduce parasite  
> solutions. When you use numeric parameters Solve can verify which of  
> theses are correct. The rest of the discussion is totally besides the  
> point, and so is using Reduce (for example, because one can easily come  
> up with equations that Reduce will not manage).
> The example was meant to illustrate the very trivial and elementary fact  
> that the world is full of functions with parameters that can be  
> evaluated pointwise (once numeric parameters have been substituted) but  
> cannot be evaluated by Evaluate. This is so basic and there are so many  
> examples of it that I do not see any point in discussion this farther.
>
> Andrzej Kozlowski
>
>



-- 
DrMajorBob at longhorns.com