Ralf Hemmecke wrote:
> Does someone find this behaviour natural? (FriCAS 1.0.9)
>
> (1) -> solve([x^2 = 1],[x,y])
>
>
> (1) [[x= 1],[x= - 1]]
> Type: List(List(Equation(Fraction(Polynomial(Integer)))))
>
> (2) -> solve([x^2 = 1,y^2=1],[x,y,z])
>
> >> Error detected within library code:
> system does not have a finite number of solutions
>
> It's probably the algorithm that leads to the behaviour of (2). But even
> if there were no good algorithm to determine the solution of this
> system, showing ">> Error detected within library code:" is certainly
> frightening to the end user. It sounds like, there is a bug in the library.
>
> The offending line is
>
> groebSolve(leq: L DPoly,lvar:L OV) : L L DPoly ==
> lnp:=[dmpToHdmp(f) for f in leq]
> leq1:=groebner lnp
> #(leq1) = 1 and first(leq1) = 1 => list empty()
> not (zeroDim?(leq1,lvar)) =>
> error "system does not have a finite number of solutions"
> -- add computation of dimension, for a more useful error
>
> Well, the bug is that it should just show "system does not have a finite
> number of solutions", but not this ">> Error" message.
>
> Other opinions?
1) Currently we _have to_ call error, because the 'solve' routine
can not deliver promised result. The only alternative we have
now it to return some garbage and this may lead to wrong results.
2) There are reasonable ways to solve positive dimensional system,
simply no is implemented in FriCAS. In light of this error is
resonable -- it inform user about system defect (unimplemented
routine).
3) Since users were frightened by word "error" Poplog system
decided to use word "mishap". Theoretically we could do
something like this, but I think that such wording would be
misleading and on average do more harm than help.
--
Waldek Hebisch
[email protected]
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