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/CAKgW%3D6%2BDXE-qSq_TkD4K0Op_8-1gmA3%2BQN8VYcR4Q%2BLq%3D%3DMFmg%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
