Guido van Rossum added the comment: > Ok, so if I understand correctly, the ideal thing would be to > implement decimal to binary conversion by ourselves. This would make > str <-> float conversion do the same thing on all platforms, and would > make repr(1.1)=='1.1'. This would also allow us to define exactly how > floats operate, with regard to infinities and NaNs. All this is for > IEEE-754 platforms -- for the rare platforms which don't support it, > the current state remains.
Does doubledigits.c not work for non-754 platforms? > However, I don't think I'm going, in the near future, to add a decimal > to binary implementation -- the Tcl code looks very nice, but it's > quite complicated and I don't want to fiddle with it right now. Fair enough. And the glibc code is better anyway, according to Tim. (Although probably even more complex.) > If nobody is going to implement the correctly rounding decimal to > binary conversion, then I see three options: > 1. Revert to previous situation That would be sad since we're so close. > 2. Keep the binary to shortest decimal routine and use it only when we > know that the system's decimal to binary routine is correctly rounding > (we can check - perhaps Microsoft has changed theirs?) Tim says you can't check (test) for this -- you have to prove it from source, or trust the vendor's documentation. I would have no idea where to find this documented. > 3. Keep the binary to shortest decimal routine and drop repr(f) == f > (I don't like that option). It would mean that on platforms with unknown-correct rounding *input* the *output* would be ugly again. I wouldn't mind so much if this was only VAX or Cray; but if we had to do this on Windows it'd be a real shame. > If options 2 or 3 are chosen, we can check the 1e5 bug. First you'll have to reproduce it -- I can't afford to spend much quality time with gdb, especially since I don't understand the source code at all. Though you may be able to pinpoint a possible candidate based on the characteristics of the error -- it seems to have to do with not placing the decimal point correctly when there are trailing zeros. __________________________________ Tracker <[EMAIL PROTECTED]> <http://bugs.python.org/issue1580> __________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
