Re: [sage-devel] Re: About solve(x*abs(x)==1, x)
On Thursday, December 14, 2017 at 6:17:00 AM UTC+1, Jori Mäntysalo wrote: > > I don't use. I was asked about this by a man who teaches course about > "Computer programs for mathematics and statistics". And he is not happy > about this. > Tell him solving in general is hard, esp. if there are more than just polynomials given. -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
[sage-devel] Re: About solve(x*abs(x)==1, x)
On Thursday, December 14, 2017 at 1:36:27 AM UTC+1, rjf wrote:
>
> Whether there is a feasible "upgrade" to just use sympy's
> solve is perhaps another path.
>
Indeed, with Sage-8.1:
sage: solve(x*abs(x)==1, x, algorithm='sympy')
ValueError:
Absolute values cannot be inverted in the complex domain.
Unfortunately assumptions are not copied to SymPy at the moment see
https://trac.sagemath.org/ticket/24078
However the situation in SymPy is unclear because there are two competing
solve functions available:
In [5]: x = symbols('x', real=True)
In [6]: x.is_real
Out[6]: True
In [7]: solve(x*abs(x)-1, x)
Out[7]: [1]
In [8]: solveset(x*abs(x)-1, x)
ValueError:
Absolute values cannot be inverted in the complex domain.
Regards,
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Re: [sage-devel] Re: About solve(x*abs(x)==1, x)
On Wed, 13 Dec 2017, rjf wrote: how much of Sage are you using? If you arejust using Sage as a front end to Maxima, maybe you should just use Maxima. I don't use. I was asked about this by a man who teaches course about "Computer programs for mathematics and statistics". And he is not happy about this. -- Jori Mäntysalo
[sage-devel] Re: About solve(x*abs(x)==1, x)
how much of Sage are you using? If you are just using Sage as a front end to Maxima, maybe you should just use Maxima. The relationship of solve and to_poly_solve has been discussed from time to time in the maxima newsgroup. Whether there is a feasible "upgrade" to just use sympy's solve is perhaps another path. RJF On Wednesday, December 13, 2017 at 1:36:10 AM UTC-8, Jori Mäntysalo wrote: > > This has been discussed earlier, but I was again asked about this: > > sage: solve(x*abs(x)==1, x) > [x == (1/abs(x))] > sage: solve([x*abs(x)==1, x==x], x) > [[x == 1]] > > And yes, to_poly_solve=True can be used. But this is annoying to teach and > gives bad impression of Sage. Is there any plans to make this better? > > -- > Jori Mäntysalo > -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
