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From: oleg@okmij.org
To: christoph.hoeger@tu-berlin.de
cc: caml-list@inria.fr
Message-Id: <20141101125425.90219C38B8@www1.g3.pair.com>
Date: Sat,  1 Nov 2014 08:54:25 -0400 (EDT)
Subject: Re: [Caml-list] is it possible to embed an OCaml interpreter into
 an OCaml Module?



Christoph Hoeger wrote:

> But ist it also possible in some way to embed that interpreter safely
> in an OCaml Module (so I can reuse it e.g. from within utop)?
> Currently, it seems that there is exactly one dedicated toplevel for
> every running bytecode interpreter and when running utop, it is
> already in use.
>
> So what I would need would be the ability to execute a phrase from
> within a call of execute_phrase. I already clonded the toploop module
> and for tehe time being I am fine with that. What I need is a way to
>
> a) safe the already set ('outer') toplevel value bindings
> b) restore the nested value bindings
> c) execute the compiled bytecode
> d) restore the 'outer' value bindings

The MetaOCaml top-level does exactly what you have described. It is
the standard OCaml toplevel with the ability to execute the generated
code. Please look at the file metalib/runcode.ml in the MetaOCaml
distribution. If you get it from the metaocaml.bundle, you get the
current version. Otherwise, please to make sure the beginning of
run_bytecode starts as follows:

let run_bytecode' exp =
  if !initial_env = Env.empty then begin
    let old_time = Ident.current_time() in
    (* does Ident.reinit() and may corrupt the timestamp if we
       run in top-level. See Ident.reinit code
     *)
    initial_env := Compmisc.initial_env(); 
    Ident.set_current_time old_time
   end;
  (* Ctype.init_def(Ident.current_time());  *)
  ....