announce: callbacks-0.1

[Christophe Raffalli <christophe.raffalli@univ-savoie.fr>]

link: third item of:

http://www.lama.univ-savoie.fr/~raffalli/?page=soft&lang=en

comment and idea are welcome !

-----------
MOTIVATION
-----------

callbacks are problematic when writting OCaml bindings for C
library. Indeed, a C function waits for a function respecting C
calling conventions as argument, and OCaml functions do not respect the
C conventions.

Then in a library you only have a limited number of the C functions and
in fact ideally, it is the user of the library that should often write 
the C function that needs to be passed in arguments to other C functions.

This is too hard for the average user ... this is why I wrote this package


Here is an example on how to use it (see the README file for a more 
detailled doc)

--------------
in glut.mli:
--------------

open Direct_callback
...
val reshapeFunc: cb:(w:int->h:int->unit) callback->unit
...

-------------
in a programm using lablGlut
-------------

let doReshape ~w ~h =
   ...

c_wrapper doReshape_cb for  doReshape : w:int->h:int->unit
...

ReshapeFunc doReshape_cb
...


-------------
in glut.ml
-------------

open Direct_callback
...
external reshapeFunc : cb:(w:int->h:int->unit) callback->unit = 
"ml_glutReshapeFunc"
...

-------------
in wrapglut.c
-------------

...
ML_1(glutReshapeFunc,Callback2)
...

which expends to

...
CAMLprim value ml_glutReshapeFunc (value arg1) \
{ glutReshapeFunc ((void (*)(int,int))(arg1)); return Val_unit; }
...