"Delayed" problem in mfunction/mmacro definition

Mathematica's evaluation process is
(a) too complicated.
(b) not deterministic.

It can only partially be explained by reading the reference
book, appendix A4.1-4.4
but then read about Update, which says in part,

One special circumstance is that changes in the value of one
 symbol can affect the value of another symbol by changing
the outcome of Condition tests. In such cases, you may need
to use Update on the symbol you think may be affected.

So, you MAY NEED to use a function Update to get the right answer. But 
maybe not.

Macsyma is not as clear as it should be, but people did not have so much 
experience
in 1967.  Mathematica doesn't have that excuse.

RJF

Siver Andrey wrote:

>----- Original Message ----- 
>From: "Richard Fateman" <fateman at cs>
>To: "Siver Andrey" <siver@sirius.ihep.su>
>Cc: "Maxima-List" <maxima@math.utexas.edu>
>Sent: Monday, November 15, 2004 7:03 PM
>Subject: Re: [Maxima] "Delayed" problem in mfunction/mmacro definition
>
>
>  
>
>>I think Albert Reiner gave a pretty good answer, but
>>the underlying question "How does one do evaluation the
>>way Mathematica does, using Maxima?" is very suspicious.
>>
>>1. Mathematica has a rather different model of evaluation
>>from anything else.  I would guess that 99% of Mathematica
>>users understand only a small part of it. Fortunately,
>>that is sufficient for most users.
>>
>>2. Mathematica's evaluation model involves pattern matching,
>>non-deterministic rules that supposedly prevent infinite
>>evaluation, but are secret.
>>
>>3. A detailed examination involving Hold, Evaluate, Delay, etc etc
>>in Mathematica suggests it is a really bad model.
>>    
>>
>
>Why is it bad? How it could be represented or explained?
>
>  
>
>>If you want to use Maxima, I suggest you learn about the evaluation
>>model in Maxima, NOT by comparison with Mathematica.
>>    
>>
>
>And how could I learn about the evaluation model in Maxima?
>

I suggest you learn Lisp, to see a symbolic language.

>
>
>Thanks for Your answers and help.
>
>
>Andrey S.
>
>
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>