[cwn] Attn: Development Editor, Latest Caml Weekly News

Tue Nov 28 01:38:04 PST 2006

Hello,

Here is the latest Caml Weekly News, for the week of November 21 to  
28, 2006.

1) Inotify binding
2) OCaml Tutorial - in French, Italian and Japanese
3) float rounding

========================================================================
1) Inotify binding
Archive: <http://groups.google.com/group/fa.caml/browse_thread/thread/ 
65b9e6b67afbb553/82de5c2e53096a47#82de5c2e53096a47>
------------------------------------------------------------------------
** Vincent Hanquez announced:

I've made a small bindings for inotify, aka linux file system  
notification
new subsystem.

It's available here:

<http://tab.snarc.org/projects/ocaml_inotify/>

or the archive is directly here:

<http://tab.snarc.org/download/ocaml/ocaml_inotify-0.2.tar.bz2>

You need a really recent glibc to have inotify syscall available
through /usr/include/sys/inotify.h. I didn't bother putting some code
to handle old glibc, but I accept patch :)

The archive contains an example program on how to use the interface.

** Richard Jones then said:

I think OMake includes bindings for gamin.  Or FAM which is the older
SGI-based daemon, but gamin is C API compatible with FAM.

<http://svn.metaprl.org/viewvc/mojave/omake/src/clib/omake_notify.c? 
revision=1326&view=markup&pathrev=1326>
<http://www.gnome.org/~veillard/gamin/>

** Vincent Hanquez answered:

 > I think OMake includes bindings for gamin.

it seems to be talking FAM.
 > Or FAM which is the older
 > SGI-based daemon, but gamin is C API compatible with FAM.

Sounds more like a bad thing than a good thing to me.
Direct inotify binding are much smaller/simpler anyway.

========================================================================
2) OCaml Tutorial - in French, Italian and Japanese
Archive: <http://groups.google.com/group/fa.caml/browse_thread/thread/ 
c2d9e5818b899795/20b9f4155661a0a1#20b9f4155661a0a1>
------------------------------------------------------------------------
** Richard Jones announced:

Thanks to the brilliant efforts over many months by Martin Jambon,
Camarade_Tux, Luca Brivio, simo.magic, ukai, teruakigemma, and
Yamagata Yoriyuki [1] [2] the OCaml tutorial has now been
translated into 3 other languages:
French:         <http://www.ocaml-tutorial.org/fr>
Italian:        <http://www.ocaml-tutorial.org/it>
Japanese:       <http://www.ocaml-tutorial.org/ja>
(And English at <http://www.ocaml-tutorial.org/> )

The Merjis contributions are now all public domain, and those of the
other contributors are copyrighted by them respectively.

Rich.

[1] I sincerely apologise if I have missed out any of the translators
from this list.

[2] And don't forget all the people who helped write the English
version <http://www.ocaml-tutorial.org/#Acknowledgements> .

========================================================================
3) float rounding
Archive: <http://groups.google.com/group/fa.caml/browse_thread/thread/ 
8cced5418a89870a/>
------------------------------------------------------------------------
** Deep in this thread, David Monniaux said:

In C, if you are really concerned about getting your exact constants up
to the last bit, you should use the hexadecimal float notation
introduced in C99. You should also use "%a" or "%A" to print out your
floating-point values in hexadecimal if you intend to reload them on
another IEEE-754 system in a portable way.
(Unfortunately on OCaml, %a is already used for another use... Xavier,
what do you think of adding the hexadecimal float conversion to the
family of printf functions?)

Anyway, "IEEE-754 compliant", as used by common vendors, is a fairly
vague claim. For instance, contrary to a commonly held belief, the same
C or Caml program ran on two different major platforms (say, IA32 vs
AMD64 or IA32 vs PowerPC) can give different results, possibly even
depending on compiler options, and this has nothing to do with how they
parse constants... You might wish to read my preprint:
<http://www.di.ens.fr/~monniaux/biblio/pitfalls_of_floating_point.pdf>

The only widespread language that I know about that has fixed semantics
for floating-point is Java if the 'strictfp' modifier is used.
(Originally, Java was supposed to have a fully fixed semantics, but they
realized that implementing it over the 80387 compatible floating-point
stack was difficult and that it also precluded some optimizations, so
they relaxed it by default and introduced 'strictfp'. Goodbye
predictability.)

** Probably replying to an off-list message, David Monniaux then said:

In the Astrée project, we use some small C functions and OCaml wrappers
to change rounding modes. It's not easy (some systems have
fpgetround/fpsetround, others fegetround/fesetround, some have none and
you have to use assembly, and old versions of GNU libc on IA32 have
fegetround/fesetround that change rounding for the 387 FPU but not for
SSE, which may break some external C libraries).
[ Hey, we should publish our libraries. ]
In addition, some C libraries don't work properly when rounding is not
"round to nearest". I filed bugs against FreeBSD libc (printf doesn't
work properly with some arguments) and GNU libc (pow() does not work
properly).

Rounding modes other than the default "round to nearest" tend to be
largely untested on many systems and libraries, because few people use
them. #pragma FENV_ACCESS is not even implemented on gcc;
-frounding-math is supposed to signal rounding modes other than round to
nearest, but the documentation states that it's not even sure it  
works...

Not that I want to advertise myself too much, but I think you should  
read
<http://www.di.ens.fr/~monniaux/biblio/pitfalls_of_floating_point.pdf>
if you are concerned about interactions between compilers and
floating-point.

========================================================================
Using folding to read the cwn in vim 6+
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Here is a quick trick to help you read this CWN if you are viewing it  
using
vim (version 6 or greater).

:set foldmethod=expr
:set foldexpr=getline(v:lnum)=~'^=\\{78}$'?'<1':1
zM
If you know of a better way, please let me know.

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Old cwn
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========================================================================

-- 
Alan Schmitt <http://alan.petitepomme.net/>

The hacker: someone who figured things out and made something cool  
happen.
  .O.
  ..O
  OOO

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