Updates:
Status: Accepted
Labels: NeedsReview asmeurer
Comment #3 on issue 2304 by asmeurer: Remove Pure from top-level namespace
http://code.google.com/p/sympy/issues/detail?id=2304
I decided to just remove Pure completely. It was only being used as a
generator for the polynomials returned by minimal_polynomial() and
primitive_element(), but these in my opinion should require a generator
(this is how Mathematica does it, see
http://reference.wolfram.com/mathematica/AlgebraicNumberFields/ref/MinimalPolynomial.html).
The only other place that it was being used was in ode as the generator for
RootOf, but RootOf is smart enough these days to compare equal if the
polynomial is the same but the generator is different, so I just changed
that back to using a regular Dummy.
I came to the conclusion in doing this that what we need is not a Pure
Symbol, but a PurePoly, which can represent a pure polynomial. This would
behave like
PurePoly(x**2 + x + 1, x) == PurePoly(y**2 + y + 1, y)
True
PurePoly(x*y + y**2, x, y) == PurePoly(t*z + t**2, z, t)
True
This would be a subclass of Poly, and would be what is used internally in
AlgebraicNumber and RootOf instead of a Poly with Dummy generators.
See https://github.com/sympy/sympy/pull/367.
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