issue opened at https://github.com/sympy/sympy/issues/9123
On Wednesday, March 11, 2015 at 2:05:50 PM UTC-5, Aaron Meurer wrote: > > 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] > <javascript:>> 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] <javascript:>. > > To post to this group, send email to [email protected] > <javascript:>. > > 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/f1c28961-d7be-4811-ba61-0fee6ac22fe0%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
