[LON-CAPA-users] catching maxima errors

[Peter Dencker]

Hi Gerd,

below I give a simple example. The input of 'x)' (an example, the
parentheses are not balanced) causes the 'Internal error ...'.

Thanks.

- Peter


<problem>

<script type="loncapa/perl">
  $result = 'x';
</script>

<startouttext />
  Type a maxima formula equivalent to 'x'.
<endouttext />

<customresponse id="p0r0">

  <answer type="loncapa/perl">
    $bool = &cas('maxima',"is(ratexpand($submission = $result))") ;
    if ( $bool eq 'true') {return  'EXACT_ANS';};
    if ( $bool eq 'false') {return  'INCORRECT';};
    return 'BAD_FORMULA';
  </answer>

 <startouttext />
   <br /> <textline readonly="no" />  <br />
 <endouttext />

</customresponse>

</problem>




Gerd Kortemeyer schrieb:
> Hi,
> 
> On Nov 26, 2012, at 10:00 AM, Peter Dencker <dencker at math.uni-luebeck.de> wrote:
>>
>> executing a syntactically incorrect answer with maxima using
>> customresponse causes a crash remark 'Internal error ...' and  a  'bomb'
>> in the construction space of the author. In comparison, mathresponse
>> returns 'BAD_FORMULA'.
> 
> Something else must be wrong inside <customresponse>. A call to &cas() inside <customresponse> will always just return whatever the last output of MAXIMA was, which is either the result or a MAXIMA error message; no possibility of an internal error, unless there is an error inside the surrounding Perl code or an invalid value is returned from <customresponse> answer script.
> 
> - Gerd.
> 
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