Hello

Here is the latest Caml Weekly News, for the week of 17 to 24 February, 2004.

1. problems with caml-list
2. mod_caml question
3. Embedding OCaml
4. ocamldbi 0.9.0 and mod_caml 1.1.0
5. Request for more String functions
6. GtkSpell binding

This is a list administration message:

Due to an incorrect mail filtering rule recently triggered by a
software update on INRIA's mail exchangers, all messages posted to
caml-list@inria.fr the last week or so were not distributed to the
list, and were actually lost.  (For a while, I thought everyone was
just unusually quiet :-)

I hope this problem is now fixed.  Profuse apologies for the
inconvenience.
    

> So what's the role of the caml executable?  I read the apache handler
> code, and it looks like from the standpoint of the mod_caml c code, it's
> bytecode which is loaded by the caml interpreter.  But why's it
> executable?  Are there other usages?

It's simply there to workaround a problem with Dynlink.

In brief when you use Dynlink, it tries to read your current
executable to find the symbol table in the bytecode.  This way it can
find out what symbols are already part of the environment.

Of course there are all sorts of problems with doing this in a Unix
environment: eg. you might, quite legitimately, have unlink(2)ed the
executable, so it no longer exists.  Or you might not have read
permission on your own executable.  Or you might not be able to find
the path to your own executable (think chroot(2), or being passed a
non-standard argv or PATH).  etc.

The problem with mod_caml is that there's no executable at all,
because the module is dynamically linked (using dlopen(3)) into
Apache.  Thus we have to go through some hoops to build a fake
executable and tell Dynlink to use this to find its symbol table.
This is the purpose of the code in mod_caml_c:init().
    

> Hello,
> 
> I am trying to embedd OCaml into Aolserver as second interpreter. 
> Aolserver is multithreaded web server which uses Tcl
> as scripting language. Requestes are processed concurrently by calling 
> Tcl scripts. My intention is to add OCaml
> to Aolserver so web pages written in Caml can be used for web programming.
> 
> My question is, is it safe to use OCaml in such environment where many 
> different OCaml scripts can be executed.

Have a look at this posting:

http://caml.inria.fr/archives/200308/msg00258.html

> I use Dynalink pacjage for dynamically loading object .cmo files.

Dynlink is very fussy.  I had lots of problems with it.  You might
like to look at mod_caml for ideas.
    

Richard Jones wrote:
>On Fri, Feb 20, 2004 at 12:34:12PM -0500, Vlad Seryakov wrote:
>
>>Thanks
>>
>>Actually i checked mod_caml and used many great ideas from it. I have my 
>>module
>>working fine and actually i do not use separate executable as mod_caml 
>>does. i was able to put Caml bytecode
>>runtime into shared library and give that shared library to caml_main on 
>>startup, so Dynalink is happy as well.
>
>
>Can you show me how you did this?  I'm very interested.
>
>Rich.

Sure, sorry

Module can be downloaded from http://www.crystalballinc.com/vlad/software/
    

I have got another solution to possibly resolve this
problem:
I've developed an embedded O'Caml toplevel
which integrates the runtime and the compiler of O'Caml.
Actually, it's a dynamic linked library (in C) builds using
the "ouput-obj" option; i have solved the problem of
the symbole table thanks to a modification of the
compiler and the runtime.

you can download the patch at this url:
http://www.pps.jussieu.fr/~capel/eng/toplevel/toplevel.html

you will find also an O'Caml plugin for Excel and Netscape in this page.


Just an example to show you how it works (in C):
(you can also use the directives #use and #load)

  toplevel_init(argv);

  toplevel_exec("let rec ack m n =
                 match m,n with 0,n -> n+1
               | m,0 -> ack (m-1) 1
               | m,n -> (ack (m-1) ack m (n-1))");

  val = toplevel_exec("ack 3 2;;");
  res = 1+Long_val(val);

  printf ("1+ack(3,2)=%dn", res);


I hope it will help you.
    

I'm pleased to announce that the DBI (database layer) part of mod_caml
has now been split into a separate library, so you can try it out
independently of mod_caml itself.  You can find both packages in the
mod_caml CVS repository:

http://savannah.nongnu.org/cgi-bin/viewcvs/modcaml/

Or you can check them out of CVS by following the instructions on this
page, under the heading "Anonymous CVS Access":

https://savannah.nongnu.org/cvs/?group=modcaml

(I haven't built tarballs at the moment, because it's all somewhat
experimental)
    

> > val split : string -> char -> int -> string list
> > val split_chars : string -> char list -> int -> string list
> > val strstr : string -> string -> int -> int
> > val ends_with : string -> string -> bool
> > val begins_with : string -> string -> bool
> > val string_of_chars : char list -> string
>
> Yes, ends_with and begins_with - I keep copying those functions from
> file to file.  It'd be great to have them in the std lib.

<Plug> Many of these (And everything the OP asked for, though I had to add
some of them just now) are in my extlib library
(http://raevnos.pennmush.org/code/extlib/), though under different names.
It's a collection of things that would be useful in the standard libraries
that come with ocaml, but aren't there. I keep adding to it all the time
(Also just added the getpgid/setpgid functions also just requested on the
list).

>
> Along with:
>

> String.truncate  - truncate a string to a given length

This one's in it too.

</Plug>
    

GtkSpell (http://gtkspell.sf.net) is a library for doing on-the-fly spell
checking in gtk text widgets. I've whipped up bindings to use it with
lablgtk2.

See http://raevnos.pennmush.org/code/lablgtkspell/ for source, docs, etc.

It was interesting, because I've never looked at how lablgtk2 works under
the hood (Just using the high-level objects), and now had to get at the
actual C pointers of things. Happily, it turned out to be easy to figure
out from the source. :)
    

Using folding to read the cwn in vim 6+

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.

Old cwn

If you happen to miss a CWN, you can send me a message and I'll mail it to you, or go take a look at the archive or the RSS feed of the archives.

If you also wish to receive it every week by mail, you may subscribe online.

Alan Schmitt