#15902: catch maxima RuntimeErrors and rethrow usefully
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Reporter: rws | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.2
Component: interfaces | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Comment (by nbruin):
There may be several ways of approaching this problem. The main reason why
this runtime error occurs is illustrated by:
{{{
sage: from sage.interfaces.maxima_lib import maxima_eval
sage: maxima_eval("#$1+$")
RuntimeError: ECL says: THROW: The catch MACSYMA-QUIT is undefined.
sage: type(maxima_eval)
<type 'sage.libs.ecl.EclObject'>
}}}
The problem is that `maxima_eval` itself is a wrapper around a lisp
function. When called with a string argument, the default is to convert
that string to a lisp expression via the lisp "reader" (think parser). The
`"#$...$"` construct is a reader "macro": it calls the maxima parser on
the string. Problem is, this happens ''before'' `maxima_eval` takes
control (which does set up the appropriate error catching infrastructure
for maxima code).
We should run the reader under the same error catching:
{{{
sage: maxima_eval('(read-from-string "#$1+$")')
RuntimeError: ECL says: Maxima condition. result:T$error:No error.
}}}
As you can see, now the error does get processed in a different way. No
useful error message comes out of it, though.
When I wrote this, it was really with the idea that it would be an error
of the calculus library if maxima were fed a syntax error. Nearly all the
translation between sage and maxima can be done on a deeper level than
string back-and-forth parsing. See `sr_to_max` and `max_to_sr` and how
they are used in `sr_integral`, `sr_limit` and `sr_sum`. It was originally
the idea that the calculus-to-maxima_lib interface would eventually almost
do away completely with string passing. As it turned out, this hasn't been
such a priority.
In my opinion, `symbolic_expression_from_maxima_string` should only
receive strings that parse in maxima. Those are the ones that give the
incomprehensible error message. Actual runtime errors are caught in a
meaningful way:
{{{
sage: sage.calculus.calculus.symbolic_expression_from_maxima_string("1/0")
RuntimeError: ECL says: Error executing code in Maxima: expt: undefined: 0
to a negative exponent.
}}}
--
Ticket URL: <http://trac.sagemath.org/ticket/15902#comment:1>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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