Great. This doesn't address the issue in the assumptions system, though. An issue should still be opened for that.
Aaron Meurer On Fri, Sep 20, 2013 at 12:21 PM, mario <[email protected]> wrote: > I submitted https://github.com/sympy/sympy/pull/2470 to fix this. > > > On Wednesday, September 11, 2013 12:36:56 PM UTC+2, Thilina Rathnayake > wrote: >> >> Hi All, >> >> I am trying to implement the solutions for cubic Thue equation and to do >> that >> I have to solve cubic equations. I use `solve()` to do this. But I am >> having a little >> trouble filtering out real solutions from the solution list returned by >> `solve()`. >> >> I tried the following. >> >>> In [5]: from sympy.abc import x >>> In [6]: solutions = solve(2*x**3 - 3*x**2 - 3*x - 1) >>> >>> In [8]: for s in solutions: >>> ...: print(sympify(s).is_real) >>> ...: >>> None >>> None >>> None >> >> >> But one of the solutions in this equation is real. See below: >> http://www.wolframalpha.com/input/?i=2*x**3+-+3*x**2+-+3*x+-+1 >> >> That is also included in the list returned by `solve()` >> >>> In [9]: solutions[0] >>> Out[9]: 1/2 - (-3)**(1/3)/2 + (-3)**(2/3)/2 >> >> >> But, Interestingly, >> >>> In [10]: for s in solutions: >>> ....: print(im(s)) >>> ....: >>> -3**(5/6)/4 + 3*3**(1/6)/4 >>> im((-3)**(2/3)/(-1/2 + sqrt(3)*I/2))/2 - im((-3)**(1/3)*(-1/2 + >>> sqrt(3)*I/2))/2 >>> im((-3)**(2/3)/(-1/2 - sqrt(3)*I/2))/2 - im((-3)**(1/3)*(-1/2 - >>> sqrt(3)*I/2))/2 >> >> >> `im()` of `solutions[0]` should be zero. Am I doing something wrong here >> or is this a bug? >> Are there any other methods to find whether a number is purely real or >> not? >> >> Thank you in advance. >> >> Regards, >> Thilina. >> > -- > You received this message because you are subscribed to the Google Groups > "sympy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/sympy. > For more options, visit https://groups.google.com/groups/opt_out. -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/sympy. For more options, visit https://groups.google.com/groups/opt_out.
