Comment #2 on issue 1985 by asmeurer: as_real_imag() gives wrong answer
when expanding quotient
http://code.google.com/p/sympy/issues/detail?id=1985
The recursion is because re() calls as_real_imag on it's argument to get
the real part, whereas .as_real_imag() calls expand(complex=True), in
particular re()._eval_expand_complex(). So I think the deep=False was
intentional to avoid infinite recursion. So if you change that, you have
to change something else too to provide a base case for the recursion.
The thing that bothers me is this (from Expr.as_real_imag())
for term in args:
coeff = term.as_coefficient(S.ImaginaryUnit)
if coeff is None:
re_part.append(term)
else:
im_part.append(coeff)
return (Add(*re_part), Add(*im_part))
As you point out, coeff is None doesn't imply that term is real, it just
implies that as_coefficient can't rewrite it as the coefficient of I. It
should be written so that if it can't know for sure, it just returns
(re(expr), im(expr)) (like how True, False, and None work in the new
assumptions). I'm not sure how this can be done, though. Any ideas?
--
You received this message because you are subscribed to the Google Groups
"sympy-issues" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/sympy-issues?hl=en.
