Updates:
Cc: -mrock...@gmail.com -ness...@googlemail.com -ronan.l...@gmail.com
Comment #1 on issue 3929 by ronan.l...@gmail.com: New assumptions handlers
should use logic satisfiability as much as possible
http://code.google.com/p/sympy/issues/detail?id=3929
Well, it's the whole concept of handlers that is wrong. We need to be able
to tell sympy that Q.zero(x*y*z) equals Q.zero(x) | Q.zero(y) | Q.zero(z)
(assuming x, y, and z live in a division ring
(http://en.wikipedia.org/wiki/Division_ring) ). The Mul handler for Q.zero
is just a bad approximation for the pattern matching rule
Q.zero(Mul(*args)) -> Or(*[Q.zero(arg) for arg in args]).
Another problem is that not everything can be expressed with unary
predicates. To reason meaningfully about Q.zero(x+y), we need to say that
it's equal to Eq(x+y, 0).
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