Comment #24 on issue 2039 by smichr: Mul.eval_subs problems
http://code.google.com/p/sympy/issues/detail?id=2039
I'm not sure right now how powsimp and powdenest fit together...if you have
ideas I'm listening. I'll be thinking about it.
I made powdenest respect assumptions that are already present: it only
makes the assumption if expr.is_positive is None. I initially thought that
it might be good to just replace vanilla symbols with positive dummies, but
then you would get a spoiler if you had ((neg*pos)**2)**(1/2) instead of
((neg*x)**2)**(1/2) because the former would definitely be negative and the
2 non-extractable rather than "extractable under some conditions" (and thus
denestable) for the second case. On the other hand, perhaps this would be a
good way to go if automatic simplification is working since:
sqrt((n*p)**2)
-n*p
i.e., the power is taken care of automatically. But it gets ugly for odd
powers:
sqrt((n*p)**3)
I*p**(3/2)*(-n**3)**(1/2)
so perhaps it's best to go with the global assumption without applying
assumptions atomically.
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