Should negative zero (-0) be supported? It is virtually supported already;
the object 'fnzero' is defined in libmpf.py (though not used anywhere). It
just needs to be supported in standard operations, and elsewhere "x ==
fzero" needs to be replaced with something else so that -0 is not forwarded
to places where it shouldn't go.

I'm not personally convinced that signed zero is worth the trouble, but it
would be useful for allowing extended compatibility with IEEE 754
semantics, for continuity along branch cuts, etc, and could resolve some
issues in interval arithmetic (although it would also cause some more
complication).

Original issue for #167: http://code.google.com/p/mpmath/issues/detail?id=127

Original author: https://code.google.com/u/111502149103757882156/

Original owner: https://code.google.com/u/111502149103757882156/