On 18 lis, 23:54, "ma...@mendelu.cz" <ma...@mendelu.cz> wrote:
> On 18 lis, 21:49, Harald Schilly <harald.schi...@gmail.com> wrote:
>
> > I got this from the "report a problem" form, confirmed in 4.2.1
>
> > sage: solve([x==x],x)
> > gives an exception.
>
> > Maxima says this:
> > $ maxima -q
> > (%i1) solve([x=x],x);
> > (%o1) all
> > (%i2)
>
> Similar problem is
> solve(SR(0),x)
>
> and another problem is
> solve(0,x)
> - but both these cases are highly improbable. Should be the second one
> fixed or no?
>
> I think that it is easy to catch the answer 'all' in the maxima output
> and change into anything we want on output, but the question is, what
> should be the output of solve([x==x],x) and solve([x==x],x,
> solution_dict=True) in Sage
>
> btw:
>
> sage: y=var('y')
> sage: solve([x==x,y==y],[x,y])
> [[x == r2, y == r1]]
> sage:
>
> I did not look to the Maxima code (can look tomorow, we have a
> midnight in five minutes), but from the test like above it seems that
> the answer 'all' appears only for equations in one variable.
Related Maxima code is at
http://maxima.cvs.sourceforge.net/viewvc/maxima/maxima/src/solve.lisp?revision=1.25&view=markup
146 ;; Deal with special cases.
147 (cond
148 ;; Trivially true equations for any set of variables.
149 ((equal eql '(0))
150 (return '$all))
151
152 ;; Trivially false equations: return []
153 ((or (null varl) (null eql))
154 (return (make-mlist-simp)))
Another fast solution is to patch maxima file solve.lisp and replace
line 150 by something which is more resonable in Sage, but this may
break some maxima tests. Btw: is maxima build tested? (I mean the test
suite which comes with maxima, not the tests within Sage.)
R.
>
> Robert
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