# [Maxima] rtests in Maxima problem

Chris Sangwin sangwinc at for.mat.bham.ac.uk
Thu Dec 2 02:52:40 CST 2010

```Dear all,

In the library of functions I have a number of quite different senses in
which two expressions can be considered the same/different.  That is the
whole point!  A teacher will establish different properties, and then
generate outcomes based on this.  For example, they might say "your
expression is equivalent to the right answer, but you need to write the
coefficients in lowest terms".  Or, "Your expression isn't completely
factored, you need to do more work on the term ...".

I posted a .pdf document to the Maxima mailing list, which explains this
in more detail.  It was blocked, so I've posted it online here

http://web.mat.bham.ac.uk/C.J.Sangwin/tmp/AssessmentDoc.pdf

The library I have written already does these sorts of things.  I know how
difficult Maxima can be with simp:false.  I've battled against it quietly
for the last 5 years!  And it now mostly works very well.  1000s of
students are using these functions everyday and having useful feedback
provided to their online quizzes.  See
http://web.mat.bham.ac.uk/C.J.Sangwin/Publications/2010-3-1-STACK.pdf

I'm sorry to be obscure in these emails, but there are quite a lot of
interesting issues here, both educational, mathematical and from the CAS
point of view...  I would like to contribute this code as a share package
to enable more comment and criticism.  As part of this I'd like/need to
provide rtests!

The .pdf was a first draft at documentation, but I will convert this to
.texi format inline with the standard for Maxima.

I agree with Richard's earlier point that syntax is a major issue.  This
is addressed in a separate part of the assessment system, so that by the
the the student's expression gets to Maxima is is syntactically valid.
This is a non-trivial issue, but not the subject of my current difficulty
with the rtests.

I hope this helps.  I'm very sorry indeed if all this wasn't clear before.

Chris

On Thu, 2 Dec 2010, Leo Butler wrote:

>
>
> On Wed, 1 Dec 2010, Richard Fateman wrote:
>
> < On 12/1/2010 12:11 PM, Stavros Macrakis wrote:
> < > ....
> < >
> < > So ... what exactly do you mean by "giving the same answer" in the absence
> < > of simplification?
> < >
> < >
>
> If I understand the context, then Chris likely wants to allow different
> simplifications which depend on the question asked (is that right, Chris?).
> Granting that,
> I think the question is, how can the user control the simplifier so
> that only certain subsets of simplifications are carried out. The
> clean way to do this is through a policy mechanism, as I have suggested
> before.
>
> Leo
>
> --
> The University of Edinburgh is a charitable body, registered in
> Scotland, with registration number SC005336.
>
>
```