#7377: Symbolic Ring to Maxima via EclObject
---------------------------+------------------------------------------------
Reporter: nbruin | Owner: nbruin
Type: enhancement | Status: new
Priority: major | Milestone: sage-feature
Component: symbolics | Keywords:
Work_issues: | Author: Nils Bruin
Reviewer: | Merged:
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Comment(by nbruin):
I think the following email might be of interest to other people wanting
to hack maxima:
> Since there is already a decent string parser for taking Sage stuff to
> Maxima and (especially) getting back Sage stuff from Maxima, would
> there be a way to modify the above - or ecl_eval - to give back the
> Maxima expression directly? Perhaps this is already in the
> lib/ecl.pyx file, though I didn't see it on the first reading.
lib/ecl.pyx has nothing to do with maxima-specific stuff. That is all in
sagemax.py. It is actually a little bit important to keep that
distinction.
Maxima is not the only lisp program we might want to interface with.
There is {{{max_read(S) = cadadr(EclObject("#$%s"%S))}}}, which *reads*
the string
S as a maxima expression and returns its parsed result.
So {{{meval(max_read(S))}}} would do the trick. I do not know what
routines maxima
has to convert expressions to a string. If I wanted to know, I would find
it
out by looking at something like
{{{max_read("maxima-command-to-print-to-string(x)")}}}
and see what token the maxima reader puts in. I imagine you get something
like
{{{
<ECL: ((MAX-PRINT-STRING) x)>
}}}
back, So do:
{{{
maxprint:=EclObject("MAX-PRINT-STRING") #do this once globally
meval(EclObject([[maxprint], maxexpression])).python()
}}}
Indeed:
{{{
sage: max_read("string(x)")
<ECL: (($STRING) $X)>
sage: meval(max_read("string(x)"))
<ECL: "x">
sage: meval(max_read("string(x)")).python()
'"x"'
sage: meval(max_read("string(x)")).python()[1:-1]
'x'
}}}
So
{{{
sage: maxprint=EclObject("$STRING")
sage: def max_to_string(s):
....: return meval(EclObject([[maxprint],s])).python()[1:-1]
}}}
would give you a string representation. Be aware that #$...$ suffers from
performance loss, so if you repeatedly use it, your timings will go south
quickly. See Dodier's comments on this a while ago. Apparently you could
patch Maxima to lose the performance-losing routine (at the expense of
losing the wonderful linear-search history the maxima parser offers now).
> Sage command -> calls Maxima command -> Maxima command evaluated, but
> in the ECL library version, not the pexpect version -> Maxima output
> (a string) converted back using the stuff in Sage
Yes, that would be an approach virtually orthogonal to the one taken in
sagemax.py.
{{{
> sage: str(ecl_eval("#$load(to_poly_solver)$"))
> append: argument must be a non-atomic expression; found false
> -- an error. To debug this try debugmode(true);
}}}
To illustrate the inner workings:
{{{
sage: from sagemax import *
sage: e=max_read('load("to_poly_solver")')
sage: e
<ECL: (($LOAD) "to_poly_solver")>
sage: meval(e)
append: argument must be a non-atomic expression; found false
-- an error. To debug this try debugmode(true);
sage: meval(max_read("append(a,b)"))
append: argument must be a non-atomic expression; found a
-- an error. To debug this try debugmode(true);
}}}
So my guess is that "load" is trying to append to an improperly
initialized
maxima list. I guess that means that in the current setting, our maxima
environment hasn't properly been set up yet. That is no surprise. It is
actually surprising that so much of maxima works without any
initialization
at all.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/7377#comment:2>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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