Hi,
On 25 May 2011 10:43, Aaron S. Meurer <[email protected]> wrote:
> What happens if you make it use an algebraic domain, i.e., set
> extension=True?
>
That's a good suggestion. Usually polys (domains or whatever else) in not
the problem (unless there is some bug and there are still quite a few
there), but the way the module is used. We can't expect that polys will work
in all contexts without fine tuning (see sympy/polys/polyoptions.py). polys
are optimized for symbolic manipulation (simplification etc.) so in other
contexts you may need to override the defaults. Look for example into
gosper_normal() in sympy/concrete/gosper.py (the first line). Two options
(field and extension) had to be specified to adjust polys behavior to make
it useful in the context of Gosper's algorithm. Similar thing happens in
solve(). Unfortunately solve() was updated to use polys properly.
btw.
Did you notice this odd printing (- -):
In [37]: F = [(x - 5)**2 + (y - 5)**2 - 4, -(-x + 5)*(-x - 2*2**(1/S(2)) +
5) - (-y + 5)*(-y + 5)]
In [38]: F
Out[38]:
⎡ 2 2 ⎛ ⎽⎽⎽ ⎞ 2⎤
⎣(x - 5) + (y - 5) - 4, - -(x - 5)⋅⎝-x - 2⋅╲╱ 2 + 5⎠ - (-y + 5) ⎦
>
> Aaron Meurer
>
> On May 24, 2011, at 10:14 PM, smichr wrote:
>
> > One of the problems I am running into with polys is this:
> >
> >>>> p1,p2=[(x - 5)**2 + (y - 5)**2 - 4, -(-x + 5)*(-x - 2*2**(1/
> > S(2)) + 5) - (-y
> > + 5)*(-y + 5)]
> >>>> solve([p1,p2])
> > Traceback (most recent call last):
> > File "<stdin>", line 1, in <module>
> > File "sympy\solvers\solvers.py", line 236, in solve
> > solution = _solve(f, *symbols, **flags)
> > File "sympy\solvers\solvers.py", line 607, in _solve
> > soln = solve_poly_system(polys)
> > File "sympy\solvers\polysys.py", line 45, in solve_poly_system
> > return solve_generic(polys, opt)
> > File "sympy\solvers\polysys.py", line 179, in solve_generic
> > result = solve_reduced_system(polys, opt.gens, entry=True)
> > File "sympy\solvers\polysys.py", line 149, in
> > solve_reduced_system
> > raise NotImplementedError("only zero-dimensional systems
> > supported (finite n
> > umber of solutions)")
> > NotImplementedError: only zero-dimensional systems supported
> > (finite number of s
> > olutions)
> >
> > The two expressions end up getting different domains:
> > [Poly(x**2 - 10*x + y**2 - 10*y + 46, x, y, domain='ZZ'),
> > Poly(-x**2 + (-2*2**(1 /2) + 10)*x - y**2 + 10*y - 50 +
> > 10*2**(1/2), x, y, domain='EX')]
> >
> > If I get rid of the sqrt(2) then the domains are both ZZ and it works.
> >>>> p2
> > -(-x + 5)*(-x - 2*2**(1/2) + 5) - (-y + 5)**2
> >>>> _.subs(sqrt(2),2)
> > (-x + 1)*(x - 5) - (-y + 5)**2
> >>>> solve([p1,_])
> > [(4, -3**(1/2) + 5), (4, 3**(1/2) + 5)]
> >
> > What's the best way to make solve flexible so it will handle this?
> >
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Mateusz
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