Issue 1158: regression: roots of polys
http://code.google.com/p/sympy/issues/detail?id=1158
Comment #1 by mattpap:
The first case works with 'cubics' flag set:
In [1]: p1 = ((x-2)*(x+3)*(x-4)).expand()
In [2]: roots(p1, x, cubics=True)
Out[2]: {-3: 1, 2: 1, 4: 1}
which uses factor() if coefficients are in Z or Q, or cubics formula
otherwise.
The other case works without this flag because x=1 is extracted explicitly.
The
reason root() function was implemented this was is that at the time of
writing
rootfinding.py module, factorization routines were buggy and hanged often.
Now factor() is fixed and is quite fast so we can use it in roots() by
default. Feel
free to fix this issue. Just remember that factorization works only for
coefficients
in Z and Q (at the moment) and there are much cheaper tools like functional
or
square-free decomposition (which work with (almost) arbitrary
coefficients). So
factorization should be used when necessary (in the last resort).
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