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MathGroup Archive 2004

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Re: Re: Re: Re: Mathematica language issues

  • To: mathgroup at smc.vnet.net
  • Subject: [mg53158] Re: [mg53142] Re: [mg53112] Re: [mg53050] Re: Mathematica language issues
  • From: DrBob <drbob at bigfoot.com>
  • Date: Mon, 27 Dec 2004 06:41:28 -0500 (EST)
  • References: <200412241058.FAA05777@smc.vnet.net> <200412250900.EAA18524@smc.vnet.net> <97F219DA-567C-11D9-8E89-000A95B4967A@mimuw.edu.pl>
  • Reply-to: drbob at bigfoot.com
  • Sender: owner-wri-mathgroup at wolfram.com

>> If Fred's "speculations" came form an employee of WRI they could
>> have the status of "documentation" without changing a word. The
>> mystery here is simply a question of authoritativeness.

If he's correct, you mean.

Bobby

On Sat, 25 Dec 2004 22:55:10 +0900, Andrzej Kozlowski <akoz at mimuw.edu.pl> wrote:

> I am sure Fred will provide his own answers, but on the principle "the
> more the merrier" (especially at Christmas) , I thought I would
> contribute my own comments:
>
> On 25 Dec 2004, at 18:00, DrBob wrote:
>
>> Fred,
>>
>> At several points you made statements I simply don't understand. The
>> examples clarify what you meant for the most part, but I'm still
>> wondering, so here goes:
>>
>>>> Unevaluated is meant to pass unevaluated arguments to a function
>>>> body and as such it works perfectly. No one in practice is interested
>>>> in (1+1)*Unevaluated[2+2].
>>
>> Do you mean a Function body? If not, Times in that example qualifies
>> as a function body. (I think.)
>
> One uses Unevaluated to prevent a rule from being applied. This means
> that a rational person will only do it when he knows there is a rule
> that he does not want to be used. There is no normal situation where
> one would use Unevaluated and there was no specific evaluation one
> wanted to prevent.
>
>>
>>>> If now no rules for f can be applied, Mathematica returns the result
>>>> so far, with Unevaluated wrapped again around the labeled arguments.
>>
>> So it's only rules FOR F that matter? Does the distributive property
>> count as a rule for Times?
>
> You do not need Unevaluated to prevent the distributive rule being used
> because it is never used automatically. You need to apply something
> like Distribute etc.
>
>>
>>>> If a rule for f can be applied, the administration of arguments
>>>> that come from Unevaluated is completely skipped.
>>
>> I don't get any meaning from the phrase "administration of arguments".
>
> I think Fred meant that the rule is applied to the arguments "as
> given", without changing them or rearranging in any way.
>
>>
>>>> I first formulate my assumption (only WRI and maybe a few others
>>>> know if I am right!)
>>
>> Even if your assumption is correct (as I suspect it is), this
>> statement doesn't really square with a later claim that there's no
>> mystery.
>
> A certian mystery exists even when we have full documentation, because
> even that is only a description of expected behaviour of Mathematica
> and does not include the actual mechanism behind the behaviour (of
> which at most a vague idea is provided). Everything else requires the
> source code. If Fred's "speculations" came form an employee of WRI they
> could have the status of "documentation" without changing a word. The
> mystery here is simply a question of authoritativeness.
>
>
> Andrzej Kozlowski
> Chiba, Japan
> http://www.akikoz.net/~andrzej/
> http://www.mimuw.edu.pl/~akoz/
>
>
>
>



-- 
DrBob at bigfoot.com
www.eclecticdreams.net


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