This is definitely a bug. It looks like expand(complex=True) works. This is different from expand_complex in that it also calls the other expand methods too, so that it really ends up calling it on 1/(1 - I) and I/(1 - I). So for now, I guess you will have to use expand(expr, complex=True).as_real_imag(). But add a note that just as_real_imag() should work.
Can you open an issue at http://code.google.com/p/sympy/issues/list about this. If you want, you can also look into fixing it. Since (1 + I)/(1 - I) is represented as Mul(1 + I, Pow(1 - I, -1)), the relevant code is Mul.as_real_imag in sympy/core/mul.py. It looks like the algorithm is not very general there. I think it works for 1/(1 - I) and I/(1 - I) because it works when one of the arguments is completely real or completely imaginary, but it should probably split it in the general case, at least when deep=True. Let me know if you want to take a shot at fixing this, and I can help you out if you can't figure something out. Aaron Meurer On Tue, Sep 3, 2013 at 11:19 AM, Chetna Gupta <cheta....@gmail.com> wrote: > Inorder to get the real and imaginary parts of an irrational function, i > have tried the following functions > 1) as_real_imag() > 2) expand_complex() > > While they work for most of the cases, both of them seem to fail when I > have irrational functions in the denominator. > > For example for the case (i + i)/(i-I) I get the following outputs and not > simply 0, i. Could someone suggest wayout to derive the real and imag parts > for such cases other than above. While i have implemented a method for > doing the same in https://github.com/sympy/sympy/pull/2380/files#L5R82_ > (that is real_imag in prde.py) it does not takes into account more general > cases. Any suggestions for making it to work for cases when I have > arbitrary expressions, not just rational functions as coefficients of the > arguments > > > <https://lh4.googleusercontent.com/-lV8yyuvCwsY/UiYXK3BOz1I/AAAAAAAAB08/iQrn_o7gta0/s1600/Screenshot+from+2013-09-03+22%3A36%3A17.png> > > -- > 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 sympy+unsubscr...@googlegroups.com. > To post to this group, send email to sympy@googlegroups.com. > 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 sympy+unsubscr...@googlegroups.com. To post to this group, send email to sympy@googlegroups.com. Visit this group at http://groups.google.com/group/sympy. For more options, visit https://groups.google.com/groups/opt_out.
