[spambayes-dev] RE: [Python-Dev] RE: [Spambayes] Question (orpossibly a bug report)

Tim Peters tim.one at comcast.net
Fri Jul 25 04:13:46 EDT 2003

[martin at v.loewis.de]
> While the feature is desirable, I don't like the patch it all. It
> copies the relevant code of Gnome glib, and I
> a) doubt it works on all systems we care about, and
> b) is too much code for us to maintain, and
> c) introduces yet another license (although the true authors
>    of that code would be willing to relicense it)

OTOH, even assuming "C" locale, Python's float<->string story varies across
platforms anyway, due to different C libraries treating things like
infinities, NaNs, signed zeroes, and the number of digits displayed in an
exponent differently.  This also has bad consequences, although one-platform
programmers usually don't notice them (Windows programmers do more than
most, because MS's C library can't read back the strings it produces for
NaNs and infinities -- which Python also produces and can't read back in

So it's not that the patch is too much code to maintain, it's not enough
code to do the whole job <0.9 wink>.

> It would be better if system functions could be found for a
> locale-agnostic atof/strtod on all systems. For example, glibc
> has a strtod_l function, which expects a locale_t in addition
> to the char*.

Well, a growing pile of funky platform #ifdefs isn't all that attractive

> It would be good if something similar was discovered for VC. Using
> undocumented or straight Win32 API functions would be fine.

Only half joking, I expect that anything using the native Win32 API would
end up being as big as the glib patch.

> Unfortunately, the "true" source of atof (i.e. from conv.obj) is not
> shipped with MSVC :-(

Would that help us if we could get it?  I'm not sure how.  I expect the true
source is assembler, for easy exploitation of helpful Pentium FPU gimmicks
you can't get at reliably from C code.  Standard-quality float<->string
routines require simulating (by hook or by crook) more precision than the
float type has, and access to the Pentium's extended-precision float type
can replace pages of convoluted C with a few machine instructions.

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