The foo.expand() - foo.apart(xi_s).expand() issue is there for me on the master version of SymPy.
Aaron Meurer On Wed, Mar 11, 2015 at 1:17 PM, Chris Smith <[email protected]> wrote: > Check the version of SymPy that you are using. The development version gives > >>>> var('x y') > (x, y) >>>> apart(1/(x+y)-Rational(1,2)*x**2) > Traceback (most recent call last): > File "<stdin>", line 1, in <module> > File "sympy\utilities\decorator.py", line 35, in threaded_func > return func(expr, *args, **kwargs) > File "sympy\polys\partfrac.py", line 123, in apart > return apart(fc, x=x, full=full, **_options) > File "sympy\utilities\decorator.py", line 35, in threaded_func > return func(expr, *args, **kwargs) > File "sympy\polys\partfrac.py", line 126, in apart > "multivariate partial fraction decomposition") > NotImplementedError: multivariate partial fraction decomposition > > > On Tuesday, March 10, 2015 at 1:07:30 PM UTC-5, Aaron Meurer wrote: >> >> It looks like a bug. If you do foo.expand() - foo.apart(xi_s).expand() >> you get a term which is definitely not equal to zero. >> >> Aaron Meurer >> >> On Tue, Mar 10, 2015 at 9:57 AM, Francesco Biscani <[email protected]> >> wrote: >> > Hello list, >> > >> > I feel a bit embarrassed as probably I am doing something blatantly >> > wrong, >> > but I cannot understand what is going here. Consider this snippet (copy >> > pasted from an Ipython notebook): >> > >> > """ >> > import sympy >> > sympy.init_printing() >> > from sympy import Symbol,sqrt,cos,sin,solve,Function,atan,apart,S >> > >> > # Some symbols >> > h,n,m,M,g,t,xi_s,eta_s = [Symbol(_) for _ in >> > ['h','n','m','M','g','t',r'\xi',r'\eta']] >> > pxi,peta = [Symbol(_) for _ in [r'p_\xi',r'p_\eta']] >> > >> > # A rational expression >> > foo = >> > >> > 32*eta_s**8*g*m/(eta_s**2+xi_s**2)**3-64*eta_s**6*g*m/(eta_s**2+xi_s**2)**2-23*g/2*eta_s**2*m-7*g/2*xi_s**2*m+(320*eta_s**4*g*m**2+peta**2+pxi**2)/(8*m*(eta_s**2+xi_s**2)) >> > """ >> > >> > Now if I do "foo_apart(xi_s)", it seems like there are two parts of the >> > expression that disappear. (specifically, >> > -23*g/2*eta_s**2*m-7*g/2*xi_s**2*m >> > is not there any more). Indeed, if I do: >> > >> > """ >> > foo.apart(xi_s).expand() == foo.expand() >> > """ >> > >> > This returns False. >> > >> > My brain is a bit fried at the moment :) So what am I overlooking here? >> > >> > Cheers, >> > >> > Francesco. >> > >> > -- >> > 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. >> > To view this discussion on the web visit >> > >> > https://groups.google.com/d/msgid/sympy/CAHExjCsbts1UA_p%3DB6g-%2B6H7ny_MJomiaCjb5YgzSMAgDTs08g%40mail.gmail.com. >> > For more options, visit https://groups.google.com/d/optout. > > -- > 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. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sympy/e7daf358-3af7-4c36-b088-9ed11d6c67b4%40googlegroups.com. > > For more options, visit https://groups.google.com/d/optout. -- 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. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/CAKgW%3D6Jsm%3Df%2BxXhCV4PF8J0neJVd_JtNGmRbVg3vvLdD-a-PwQ%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
