-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 4/10/2011 01:54, James K Beard wrote: > I think the long term solution is to implement the decimal arithmetic > keywords with an open mind. Special requirements, like extremely long > decimal words (DECIMAL128 == 128 digits?????) may require multiple-precision > arithmetic, which may be problematic because most compilers support up to > quad precision floating point, which is 128 bits with 12 bits exponent and > 116 bits mantissa, or about 35 decimal digits. >
DECIMAL128 has an epsilon of 1E-33DL, I guess that means the first 33 digits after the decimal point has to be free from rounding errors. > If financial calculations were all that was required, that would be enough > for practical use, because overflow would be at 10^33 > dollars/yen/pesos/yuan/whatever. Nothing in real-world finance requires > more dynamic range. > > But, nothing in nature requires more than about 10^125, which is the ratio > of the densities of intergalactic space and the interior of a neutron star, > or the time in years for the universe to reach total heat death and an > overall homogeneous thermal composition. That's why IEEE floating points > overflow at 10^38 or, for more than 32 bits, 10^308. > > I have a multiple precision package that I use for personal work that, for > software convenience and best speed, uses a signed 16-bit integer for the > exponent and overflows at 10^9863. I've been thinking about releasing it > under the GPL but there is a lot of code cleanup needed, and some core > modules are from Numerical Recipes for Fortran 90 and will require another > license that I haven't pursued. > > James K Beard > I've talked with Kai sometime ago about licensing, GPL and LGPL aren't practical for mingw-w64, if it were, I would have taken libdecnumber and libquadmath from gcc directly. He opted for a MIT or BSD type license so mingw-w64 could still be used to develop proprietary software. I did find one with BSD license, nice decimal float support too, but its build system is so horrendous that it takes more work to fix it than actual programming. -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.16 (MingW32) iEYEARECAAYFAk2hAq0ACgkQp56AKe10wHeFZgCfQmo3NY64k/xltDCjK438gkDj 0UAAnAk42s3/1BuA24FfGal6kbncF8uF =H47M -----END PGP SIGNATURE-----
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