Case Van Horsen <cas...@gmail.com> added the comment: On Tue, Jul 7, 2009 at 1:26 AM, Mark Dickinson<rep...@bugs.python.org> wrote: > > Mark Dickinson <dicki...@gmail.com> added the comment: > > I agree this should be fixed. The conversion to float in the else > clause seems wrong to me: it can lose precision, making two unequal > values compare equal. I also agree that we should be getting > NotImplemented here. > > Do you have a patch available?
I'll upload a patch this evening. > > As an aside, I'm interested that you're implementing comparisons between > mpf and Decimal; how does that work? Do you also implement binary > arithmetic operations between mpf and Decimal? What's the result type? When I do binary operations (including comparison), I check the type of both operands. If both operands are Integer (mpz, int, long), I convert both operands to an mpz and then perform the operation. Otherwise, if both operands are Rational (mpz, int, long, mpq, Fraction), I convert both operands to an mpq. Finally, if both operands appear to be a Number (mpz, int, long, mpq, Fraction, mpf, Decimal), I convert both operands to an mpf. In the latest release of GMPY, I always return a GMPY type (unless you are converting to float or int/long). To do the conversions, I just do mpq(str(Fraction)) or mpf(str(Decimal)). I realize that the conversions aren't perfect but are probably what a user expects. The fact that GMP uses radix 2^32 or 2^64 floating point with (randomly) either [prec+1] or [prec+2] digits makes predictable floating point challenging. ;-) (prec = floor(precision_in_bits/limb_size).) In GMPY 1.04, I forced all mpf results to have [prec+1] digits but it's still messy. Time to start working on MPFR support. > > ---------- > nosy: +jyasskin, marketdickinson > > _______________________________________ > Python tracker <rep...@bugs.python.org> > <http://bugs.python.org/issue6431> > _______________________________________ > ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue6431> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
