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Camlp4. print variable value to target source.
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Date: -- (:)
From: Nicolas Pouillard <nicolas.pouillard@g...>
Subject: Re: [Caml-list] Camlp4. print variable value to target source.
Excerpts from SerP's message of Thu Sep 11 14:15:59 +0200 2008:
> On Thu, 2008-09-11 at 13:00 +0100, Jeremy Yallop wrote:
> > Quoting ?????? ??????? <serp@stork.ru>:
> > > Exitst any way to do such things?
> > >
> > > ------
> > >   let t = <:ctyp<int>> in
> > >   <:str_item<let t = ?content of t here? >>
> > 
> > I think that you're looking for this:
> > 
> >      let t = <:expr< <:ctyp<int>> >> in
> >      <:str_item<let t = $t$ >>
> > 
> > although I'm curious as to why.
> > 
> > Jeremy.
> > 
> 
> The problem what t variable result of parsing
> 
> EXTEND Gram
>   str_item:
>     [
>       [ "mtype" ; n = a_LIDENT ; "=" ; t = ctype ->
>            <:expr<
>               let f = <:expr<$t$>>
>            >>
>     ]
> END
> 
> And result now is:
> 
> let f = t
> 
> But i need to:
> 
> let f = Ast.TyId (_loc, Ast.IdLid (_loc, "int"))

You the syntactic meta lifting (as in <:expr< <:ctyp< int >> >>) is not
sufficient, you need to call the function that do this lifting.

#load "camlp4of.cma";;
open Camlp4.PreCast;;
module M = Ast.Meta.Make(Ast.Meta.MetaGhostLoc);;
let ghost = Loc.ghost;;
let t = <:ctyp@ghost< int >>;;
M.Expr.meta_ctyp ghost t;;

Best regards,

PS: Tolevel output :)

- : Camlp4.PreCast.Ast.expr =
Camlp4.PreCast.Ast.ExApp (<abstr>,
     Camlp4.PreCast.Ast.ExApp (<abstr>,
         Camlp4.PreCast.Ast.ExId (<abstr>,
              Camlp4.PreCast.Ast.IdAcc (<abstr>,
                    Camlp4.PreCast.Ast.IdUid (<abstr>, "Ast"),
                        Camlp4.PreCast.Ast.IdUid (<abstr>, "TyId"))),
           Camlp4.PreCast.Ast.ExId (<abstr>,
                Camlp4.PreCast.Ast.IdAcc (<abstr>,
                      Camlp4.PreCast.Ast.IdUid (<abstr>, "Loc"),
                          Camlp4.PreCast.Ast.IdLid (<abstr>, "ghost")))),
      Camlp4.PreCast.Ast.ExApp (<abstr>,
          Camlp4.PreCast.Ast.ExApp (<abstr>,
               Camlp4.PreCast.Ast.ExId (<abstr>,
                     Camlp4.PreCast.Ast.IdAcc (<abstr>,
                            Camlp4.PreCast.Ast.IdUid (<abstr>, "Ast"),
                                 Camlp4.PreCast.Ast.IdUid (<abstr>,
                                   "IdLid"))),
                  Camlp4.PreCast.Ast.ExId (<abstr>,
                        Camlp4.PreCast.Ast.IdAcc (<abstr>,
                               Camlp4.PreCast.Ast.IdUid (<abstr>, "Loc"),
                                    Camlp4.PreCast.Ast.IdLid (<abstr>,
                                      "ghost")))),
            Camlp4.PreCast.Ast.ExStr (<abstr>, "int")))

-- 
Nicolas Pouillard aka Ertai