Status: Valid
Owner: ----
Labels: Type-Defect Priority-Medium Solvers
New issue 3698 by [email protected]: Piecewise does solving with subs
http://code.google.com/p/sympy/issues/detail?id=3698
In [11]: Piecewise((y, Eq(z, 0)), (x**y/log(x), True)).subs(z, log(x))
Out[11]:
⎧ y for x = 1
⎪
⎪ y
⎨ x
⎪────── otherwise
⎪log(x)
⎩
In [12]: Piecewise((y, Eq(log(x), 0)), (x**y/log(x), True))
Out[12]:
⎧ y for log(x) = 0
⎪
⎪ y
⎨ x
⎪────── otherwise
⎪log(x)
⎩
This is contradictory and confusing. Both the above should give the same
thing.
Also, I don't know what the code looks like, but it's not really correct to
assume that the result of solve represents all the solutions of an
equation, since often there are solutions that solve() can't find. So this
could potentially be leading to wrong results at times.
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