camlp4 question

camlp4 question

[Christophe Raffalli]

I am writing a tool to facilitate the use of callback of camlfunction 
from C. I have a first prototype running for lablGlut, but I want to 
make it nicer using camlp4 (this extension should produce automatically 
the C wrapper for each callback, the user will only have to compile the 
produced C file).

The pb is that I need to retrieve information given in one module from 
another. The minimum I need to do is to search for the path given to 
ocamlc (the -I options) from camlp4 code, but I would prefer a better 
way, and I do not know how to retrive this PATH anyway.

Here is an example to illustrate what I need (the type 'a callback is a 
type to a C wrapper for a function of type 'a) :

-- file glut.ml, part of the lablGlut library --

...

let visibility_state_of_int = function
     0 ->  NOT_VISIBLE
   | 1 -> VISIBLE
   | _ -> raise (BadEnum "visibility_state")

REGISTER_CONVERSION visibility_state_of_int

external visibilityFunc :
   cb:(state:visibility_state_t->unit) callback->unit
    = "ml_glutVisibilityFunc"

...

-- file test.ml an example using lablGlut --

open Glut

...

let state_changed ~state =
   match value with
     NOT_VISIBLE -> printf "window not visible."; print_newline()
   | VISIBLE -> printf "window not visible."; print_newline()

MAKE_WRAPPER state_changed state_changed_cb
(* here I need to search for the convertion for the type 
visibility_state_of_int which was defined in glut.ml to make the
C wrapper state_changed_cb : (visibility_state_of_int -> unit) callback *)

let _ = Glut.visibilityFunc state_changed_cb

...

Can someone help ?

Re: camlp4 question

[Christophe Raffalli]

Yet another question ....

I was assuming you oculd ask the type of an expression in camlp4 to do 
an induction over it (the type) ....

I do not see that in the manual !

(you can only construct trees with camlp4, but you cannot match them ?)

Re: [Caml-list] Re: camlp4 question

[Martin Jambon]

On Thu, 8 Sep 2005, Christophe Raffalli wrote:

> Yet another question ....
>
> I was assuming you oculd ask the type of an expression in camlp4 to do an 
> induction over it (the type) ....

You can't, Camlp4 is only about parsing and transforming the syntax 
tree.

I imagine you could use a (complicated) 3-step approach:
1) preprocess the file with camlp4 and ignore the syntax extensions
2) compile the result with -dtypes
3) fetch the type information from the .annot file and reparse the 
original file with camlp4. This time you can get the type of 
each identifier and expand your special syntax constructs

> I do not see that in the manual !
>
> (you can only construct trees with camlp4, but you cannot match them ?)

You can use quotations in patterns to read the syntax tree. Is it what you 
mean?


Martin

--
Martin Jambon, PhD
http://martin.jambon.free.fr

Re: [Caml-list] Re: camlp4 question

[Christophe Raffalli]

Martin Jambon a écrit :
> On Thu, 8 Sep 2005, Christophe Raffalli wrote:
> 
>> Yet another question ....
>>
>> I was assuming you oculd ask the type of an expression in camlp4 to do 
>> an induction over it (the type) ....
> 
> 
> You can't, Camlp4 is only about parsing and transforming the syntax tree.
> 
> I imagine you could use a (complicated) 3-step approach:
> 1) preprocess the file with camlp4 and ignore the syntax extensions
> 2) compile the result with -dtypes
> 3) fetch the type information from the .annot file and reparse the 
> original file with camlp4. This time you can get the type of each 
> identifier and expand your special syntax constructs
> 
>> I do not see that in the manual !
>>
>> (you can only construct trees with camlp4, but you cannot match them ?)
> 
> 
> You can use quotations in patterns to read the syntax tree. Is it what 
> you mean?


Yes I saw that later (after acually using the type in MLast t odo the 
same ...)

All that lacks a lot of documentation, but in one day, I found my way ;-)

> 
> Martin
> 
> -- 
> Martin Jambon, PhD
> http://martin.jambon.free.fr

Re: [Caml-list] camlp4 question

[Martin Jambon]

On Thu, 8 Sep 2005, Christophe Raffalli wrote:

> I am writing a tool to facilitate the use of callback of camlfunction from C. 
> I have a first prototype running for lablGlut, but I want to make it nicer 
> using camlp4 (this extension should produce automatically the C wrapper for 
> each callback, the user will only have to compile the produced C file).
>
> The pb is that I need to retrieve information given in one module from 
> another. The minimum I need to do is to search for the path given to ocamlc 
> (the -I options) from camlp4 code, but I would prefer a better way, and I do 
> not know how to retrive this PATH anyway.

Maybe write a script which would transmit the -I options to camlp4o and to 
ocamlopt/ocamlc (each camlp4 loadable module can define additional options 
to pass to camlp4/camlp4o)

Martin

>
> Here is an example to illustrate what I need (the type 'a callback is a type 
> to a C wrapper for a function of type 'a) :
>
> -- file glut.ml, part of the lablGlut library --
>
> ...
>
> let visibility_state_of_int = function
>    0 ->  NOT_VISIBLE
>  | 1 -> VISIBLE
>  | _ -> raise (BadEnum "visibility_state")
>
> REGISTER_CONVERSION visibility_state_of_int
>
> external visibilityFunc :
>  cb:(state:visibility_state_t->unit) callback->unit
>   = "ml_glutVisibilityFunc"
>
> ...
>
> -- file test.ml an example using lablGlut --
>
> open Glut
>
> ...
>
> let state_changed ~state =
>  match value with
>    NOT_VISIBLE -> printf "window not visible."; print_newline()
>  | VISIBLE -> printf "window not visible."; print_newline()
>
> MAKE_WRAPPER state_changed state_changed_cb
> (* here I need to search for the convertion for the type 
> visibility_state_of_int which was defined in glut.ml to make the
> C wrapper state_changed_cb : (visibility_state_of_int -> unit) callback *)
>
> let _ = Glut.visibilityFunc state_changed_cb
>
> ...
>
> Can someone help ?
>
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--
Martin Jambon, PhD
http://martin.jambon.free.fr