How hard would it be to create a global variable that makes it so that '
always disables evaluation (even if it can be simplified like in the
cases cited below?)
Regards,
-Nathan
-----Original Message-----
From: maxima-bounces at math.utexas.edu
[mailto:maxima-bounces at math.utexas.edu] On Behalf Of Harald Geyer
Sent: Friday, October 17, 2008 5:46 AM
To: maxima at math.utexas.edu
Subject: Re: [Maxima] Problem with 'diff(x,x) tex conversion
> On Friday 17 October 2008 06:09:17 Nathaniel E. Powell wrote:
> > After playing around with this some more, I discovered that this
> > only happens for something where the expression which is being
> > differentiated is simply the variable of differentiation.
>
> Other examples:
>
> 'integrate (0, x); => 0
> 'integrate (2, x); => 2*x
> 'integrate (2*x, x); => 2*'integrate(x,x)
I think we had the discussion if evaluating functions should simplify
in simple cases in the past and did disagree.
I don't remember the details, but I think the arguments where
* if we can do it then why not to do it
* We want this to work:
(%i14) integrate(f(x)*(x-1)-x*f(x)+f(x), x);
(%o14) 'integrate(-x*f(x)+(x-1)*f(x)+f(x),x)
(%i15) expand(%);
(%o15) 0
instead of getting 'integrate(0, x)
(I'm not in that camp, I think anybody using maxima for more serious
stuff
than floating point arithmetik will need to know about nouns/verbs
anyway.)
> Sometimes it may be a bad simplification:
>
> 'diff(cos(x)*x,cos(x)*x); => 1
> diff(cos(x)*x,cos(x)*x); => Non-variable 2nd argument to diff
Thanks for providing this very nice example. I didn't know this
before. Perhaps it will help to convince somebody...
Harald
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