GNU bug report logs - #7436
[PATCH] ftoastr: new module, for lossless conversion of floats to short strings

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From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Jim Meyering <jim <at> meyering.net>
Cc: 7436 <at> debbugs.gnu.org, bug-gnulib <at> gnu.org
Subject: bug#7436: [PATCH] ftoastr: new module, for lossless conversion of floats to short strings
Date: Thu, 18 Nov 2010 09:35:20 -0800

On 11/18/10 08:36, Jim Meyering wrote:
> Before I'd looked through the code I started thinking this might
> be useful in avoiding snprintf's unhealthy need to malloc.
> Then I saw that it uses snprintf.  Oh well ;-)

There's a comment on how to fix that, for the common cases of
double on float on hosts with IEEE floating point and 64-bit ints.
It's a paper published earlier this year by Florian Loitsch
<http://dx.doi.org/10.1145/1809028.1806623>.  Not only would
this fix the malloc problem, it would run rings around sprintf,
performance-wise, on all libc implementations that I know of
that print floating-point numbers accurately.

The idea behind the latest checkin has been in Emacs for years, but the
immediate prompt for it was a bug that I found in coreutils
od, when I attempted to use it to generate floating point
numbers at random (by reading /dev/urandom).  The generated numbers
turned out to be non-random, and I tracked it down to a bug
in od.  I'll check in a fix to coreutils shortly.

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