Comment #3 on issue 978 by [email protected]: extract (-1) from all
expressions canonically
http://code.google.com/p/sympy/issues/detail?id=978
For rref(), this just shows that the simplify() flag should probably be
true with some kind of simplification (probably cancel() should be fast
enough, but strong enough for rational functions). Really, what we need
are ground domains in the matrices, but this is much more work.
The oo thing looks like a bug. It's probably related to issue 2818. Can
you investigate why it happens? I wonder if it's also related to issue
2023.
expand() should work. This shows that issue 2820 is not really fixed.
Regarding simplification, if you have a rational function, and you want to
reduce it to 0 (if it is indeed 0), then cancel() is the way to go. If the
expression is a rational function, then this will always reduce it to 0 if
it can be reduced, so if it doesn't, then you know that the expression is
not identically 0 (assuming of course that all the symbols are
algebraically independent of one another). factor() will also do it, but
much more slowly (but the result at the end will look nicer if it's not 0).
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