sympy/sympy — pull request #1677 by FireJade (2012-11-28 03:22:46+00:00)
Title: Replacing fnan with symbolic NaN

See http://code.google.com/p/sympy/issues/detail?id=3536. A few comments:

1. In some cases where fnan would fail, e.g. Float('nan').floor(), the new nan also fails.
2. One assertion removed from test_infinities() in sympy/core/tests/test_evalf.py. Since symbolic NaN is used, it doesn't make sense for it to equal sympy.mpmath.nan, since sympy.mpmath.nan would fail the "is S.NaN" check.
3. Despite subclassing Float, S.NaN.is_Float is false, since NaN behaves differently from normal float values.
4. All tests/doctests/slow tests (not marked XFAIL) pass.