Thanks a lot,

The solution from Chris covers all the requirements. A reduced subvariant of its "pa_log", compatible with camlp4 and adapted to this development has been written (probably with some errors ;-)

open Camlp4.PreCast;
open Syntax;

(* Apply a function to a list of arguments *)
value app_to_list lst _loc =
  List.fold_left
    (fun f x -> <:expr< $f$ $x$ >>)
    <:expr< Tools.log_printf >> lst;

EXTEND Gram

  expr: LEVEL "apply"
  [ [ LIDENT "log"; e = LIST0 expr LEVEL "." ->
        <:expr< Tools.log_internal ( fun () -> $app_to_list e _loc$ ) >>
       
  ] ]
;
END;


It needs the support of a module "Tools" with two functions "log_internal" and "log_printf". By example:

value log_active = ref False;

value log_printf = Printf.printf;

value log_internal e =
  if log_active.val then
  (
    e();
    print_newline();
    flush stdout;
  )
  else ();


The syntax in the callers is:

log "something is %d" 12;

Thanks to all persons who has colaborate in this subject.

-------------------------------------

Christopher L Conway wrote: 
This may not have been true of the version that was on the website
previously. I've just updated it to my latest version, which does
indeed work with camlp5.

Chris

On Nov 7, 2007 7:48 PM, Christopher L Conway <cconway@cs.nyu.edu> wrote:
  
pa_log is compatible with camlp5. In fact, that's what I use. Just
s/4/5/ all commands invoking camlp4.

Regards
Chris


On Nov 7, 2007 1:25 PM, tmp123 <tmp123@menta.net> wrote:
    
Hello,

The module "pa_log" proposed by Mr. Conway seems very near to the
objective of my previuos post.

The objective  now is expand a line like: DEBUG 3 "%d\n" 14
to: if debug.val then logint 3 ( fun () -> Printf.printf "%d\" 14  )
else ();

However, it is necessary to migrate the module to new camlpx .

Please, could someone give any advice about the current options: camlp4
or camlp5? PreCast? Functorial?

Thanks a lot.

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