camlp4 question: Mixing a printer and Ast.fold

camlp4 question: Mixing a printer and Ast.fold

[Richard Jones]

I'm trying to translate Sylvain Le Gall's gettext module to use camlp4
from ocaml 3.10.0.  The module is a printer which folds over the AST
looking for certain types of function call by name.  A simplified
version is shown below.

This program is supposed to look for all instances of a function named
f applied to a string.

I cannot for the life of me work out how to get this to compile.  I've
tried about a dozen different variations of the module names, 'open',
'include' etc. and got a dozen different errors.

----------------------------------------------------------------------
module Id = struct
  let name = "pr_gettext" 
  let version = "$Id$" 
end 

module Make (Syntax : Camlp4.Sig.Syntax)
  : Camlp4.Sig.Printer(Syntax.Ast).S =
struct
  module Loc = Syntax.Loc
  module Ast = Syntax.Ast

  class visitor = object
    inherit Ast.fold as super

    val t = []
    method t = t

    method expr = function
    | <:expr@loc< f $str:singular$ >> ->
      let t = str :: t in
      {< t = t >}

    | e -> super#expr e
  end

  let print_interf ?input_file ?output_file _ = ()

  let print_implem ?input_file ?output_file ast =
    let visitor = (new visitor)#str_item in
    let t = (visitor ast)#t in
    List.iter prerr_endline t
end

(* Register the new printer. *)
module M = Camlp4.Register.Printer(Id)(Make) 
----------------------------------------------------------------------

ocamlc -I +camlp4 -I /usr/lib64/ocaml/camlp4/Camlp4Parsers -pp camlp4of.opt camlp4lib.cma test.ml -o test.cmo
File "test.ml", line 19, characters 19-19:
Unbound constructor Ast.ExApp

Please let me know how to compile this before I go mad...

Rich.

-- 
Richard Jones
Red Hat

Re: [Caml-list] camlp4 question: Mixing a printer and Ast.fold

[Jeremy Yallop]

Richard Jones wrote:
> I cannot for the life of me work out how to get this to compile.  I've
> tried about a dozen different variations of the module names, 'open',
> 'include' etc. and got a dozen different errors.

Here's another variation that compiles and seems to work.  I changed the 
following:

    * the argument type to Make from "Syntax" to "Camlp4Syntax"
    * the register functor from "Printer" to "OCamlPrinter"
    * the accumulated value in "expr" from "str" to "singular".

Jeremy.

module Id = struct
   let name = "pr_gettext"
   let version = "$Id$"
end

module Make (Syntax : Camlp4.Sig.Camlp4Syntax)
   : Camlp4.Sig.Printer(Syntax.Ast).S =
struct
   open Syntax

   class visitor = object
     inherit Ast.fold as super

     val t = []
     method t = t

     method expr = function
     | <:expr@loc< f $str:singular$ >> ->
       let t = singular :: t in
       {< t = t >}

     | e -> super#expr e
   end

   let print_interf ?input_file ?output_file _ = ()

   let print_implem ?input_file ?output_file ast =
     let visitor = (new visitor)#str_item in
     let t = (visitor ast)#t in
     List.iter prerr_endline t
end

(* Register the new printer. *)
module M = Camlp4.Register.OCamlPrinter(Id)(Make)

Re: [Caml-list] camlp4 question: Mixing a printer and Ast.fold

[Nicolas Pouillard]

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Excerpts from Richard W.M. Jones's message of Fri Mar 21 16:06:40 +0100 2008:
> I'm trying to translate Sylvain Le Gall's gettext module to use camlp4
> from ocaml 3.10.0.  The module is a printer which folds over the AST
> looking for certain types of function call by name.  A simplified
> version is shown below.
> 
> This program is supposed to look for all instances of a function named
> f applied to a string.
> 
> I cannot for the life of me work out how to get this to compile.  I've
> tried about a dozen different variations of the module names, 'open',
> 'include' etc. and got a dozen different errors.

You where very close to something working...

Essentially three errors:

> ----------------------------------------------------------------------
> module Id = struct
>   let name = "pr_gettext" 
>   let version = "$Id$" 
> end 
> 
> module Make (Syntax : Camlp4.Sig.Syntax)

Here  it's  Camlp4.Sig.Camlp4Syntax otherwise types are abstract and you don't
have access to constructors.

>   : Camlp4.Sig.Printer(Syntax.Ast).S =
> struct
>   module Loc = Syntax.Loc
>   module Ast = Syntax.Ast
> 
>   class visitor = object
>     inherit Ast.fold as super
> 
>     val t = []
>     method t = t
> 
>     method expr = function
>     | <:expr@loc< f $str:singular$ >> ->

Here you bind loc but don't use it, however that's just a warning.

>       let t = str :: t in

Here the variable is singular not str.

>       {< t = t >}
> 
>     | e -> super#expr e
>   end
> 
>   let print_interf ?input_file ?output_file _ = ()
> 
>   let print_implem ?input_file ?output_file ast =
>     let visitor = (new visitor)#str_item in
>     let t = (visitor ast)#t in
>     List.iter prerr_endline t
> end
> 
> (* Register the new printer. *)
> module M = Camlp4.Register.Printer(Id)(Make) 

And  here it's Camlp4.Register.OCamlPrinter because Camlp4.Register.Printer is
too abstract.

I attach three working versions of it.

To compile them I use

  ocamlbuild -tags camlp4of,use_camlp4 pr_gettext.cmo

The  first  [1]  is  very  closer  to yours. However you don't really define a
proper  printer here prerr_endline, so if the goal is just to iterate over the
AST [2] is a simpler version.

But  why  make  an effect while one can easily go one step further and produce
an OCaml output that define the list of strings to be translated [3].

Cheers,

[1]: pr_gettext.ml
[2]: pr_gettext_simple.ml
[3]: pr_gettext_simple2.ml

-- 
Nicolas Pouillard aka Ertai

[-- Attachment #1.2: pr_gettext.ml --]
[-- Type: application/octet-stream, Size: 761 bytes --]

module Id = struct
  let name = "pr_gettext"
  let version = "$Id$"
end

module Make (Syntax : Camlp4.Sig.Camlp4Syntax)
  : Camlp4.Sig.Printer(Syntax.Ast).S =
struct
  module Loc = Syntax.Loc
  module Ast = Syntax.Ast
  class visitor = object
    inherit Ast.fold as super

    val t = []
    method t = t
    method expr = function
    | <:expr< f $str:singular$ >> ->
      let t = singular :: t in
      {< t = t >}
    | e -> super#expr e
  end

  let print_interf ?input_file:(_) ?output_file:(_) _ = ()

  let print_implem ?input_file:(_) ?output_file:(_) ast =
    let visitor = (new visitor)#str_item in
    let t = (visitor ast)#t in
    List.iter prerr_endline t
end
(* Register the new printer. *)
module M = Camlp4.Register.OCamlPrinter(Id)(Make)



[-- Attachment #1.3: pr_gettext_simple.ml --]
[-- Type: application/octet-stream, Size: 410 bytes --]

open Camlp4.PreCast;;

class visitor = object
  inherit Ast.fold as super

  val t = []
  method t = t
  method expr = function
  | <:expr< f $str:singular$ >> ->
    let t = singular :: t in
    {< t = t >}
  | e -> super#expr e
end;;

let filter ast =
  let visitor = (new visitor)#str_item in
  let t = (visitor ast)#t in
  List.iter prerr_endline t;
  ast
;;

AstFilters.register_str_item_filter filter;;


[-- Attachment #1.4: pr_gettext_simple2.ml --]
[-- Type: application/octet-stream, Size: 588 bytes --]

open Camlp4.PreCast;;

class visitor = object
  inherit Ast.fold as super

  val t = []
  method t = t
  method expr = function
  | <:expr< f $str:singular$ >> ->
    let t = singular :: t in
    {< t = t >}
  | e -> super#expr e
end;;

let filter ast =
  let visitor = (new visitor)#str_item in
  let t = (visitor ast)#t in
  let ghost = Loc.ghost in
  let expr =
    List.fold_right begin fun s acc ->
      <:expr@ghost< $str:s$ :: $acc$ >>
    end t <:expr@ghost< [] >>
  in <:str_item@ghost< let strings_to_translate = $exp:expr$ >>
;;

AstFilters.register_str_item_filter filter;;


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Re: [Caml-list] camlp4 question: Mixing a printer and Ast.fold

[Richard Jones]

On Fri, Mar 21, 2008 at 03:36:11PM +0000, Jeremy Yallop wrote:
> Richard Jones wrote:
> >I cannot for the life of me work out how to get this to compile.  I've
> >tried about a dozen different variations of the module names, 'open',
> >'include' etc. and got a dozen different errors.
> 
> Here's another variation that compiles and seems to work.  I changed the 
> following:
> 
>    * the argument type to Make from "Syntax" to "Camlp4Syntax"
>    * the register functor from "Printer" to "OCamlPrinter"
>    * the accumulated value in "expr" from "str" to "singular".

Brilliant, that works, thanks!

>     | <:expr@loc< f $str:singular$ >> ->
>       let t = singular :: t in

The above was just a typo when I was simplifying the program ...

Rich.

-- 
Richard Jones
Red Hat

Re: [Caml-list] camlp4 question: Mixing a printer and Ast.fold

[Richard Jones]

Thanks.  I've now got pr_gettext working again.

BTW, I think the ability to be able to map & fold over the AST is an
extraordinarily powerful feature, and deserves many more examples and
tutorials.  I know that strictly speaking it was possible before (with
Le Gall's ast-analyze extension) but the way it is done in the new
camlp4 makes the code much shorter.

Rich.

-- 
Richard Jones
Red Hat

Re: [Caml-list] camlp4 question: Mixing a printer and Ast.fold

[Richard Jones]

I'm trying to link the camlp4 module into a binary, by doing:

  ocamlc -I +camlp4 camlp4lib.cma Camlp4Bin.cmo pr_gettext.cmo \
    -o ocaml-xgettext

but my binary always prints out:

  Failure: "No implementation printer"

Apparently I need to somehow register the printer as well?  I can't
work out how to do that though.

As an aside, is mkcamlp4 supposed to do anything?  For me it always
prints this error:

  Cannot find file Camlp4.cma

Rich.

-- 
Richard Jones
Red Hat

Re: [Caml-list] camlp4 question: Mixing a printer and Ast.fold

[Nicolas Pouillard]

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Excerpts from Richard W.M. Jones's message of Fri Mar 21 17:44:30 +0100 2008:
> I'm trying to link the camlp4 module into a binary, by doing:
> 
>   ocamlc -I +camlp4 camlp4lib.cma Camlp4Bin.cmo pr_gettext.cmo \
>     -o ocaml-xgettext
> 
> but my binary always prints out:
> 
>   Failure: "No implementation printer"
> 
> Apparently I need to somehow register the printer as well?  I can't
> work out how to do that though.

What version of pr_gettext are you using?

> As an aside, is mkcamlp4 supposed to do anything?  For me it always
> prints this error:
> 
>   Cannot find file Camlp4.cma

Hum mkcamlp4 seems br0ken :(

-- 
Nicolas Pouillard aka Ertai

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Re: [Caml-list] camlp4 question: Mixing a printer and Ast.fold

[Richard Jones]

On Fri, Mar 21, 2008 at 05:50:00PM +0100, Nicolas Pouillard wrote:
> Excerpts from Richard W.M. Jones's message of Fri Mar 21 17:44:30 +0100 2008:
> > I'm trying to link the camlp4 module into a binary, by doing:
> > 
> >   ocamlc -I +camlp4 camlp4lib.cma Camlp4Bin.cmo pr_gettext.cmo \
> >     -o ocaml-xgettext
> > 
> > but my binary always prints out:
> > 
> >   Failure: "No implementation printer"
> > 
> > Apparently I need to somehow register the printer as well?  I can't
> > work out how to do that though.
> 
> What version of pr_gettext are you using?

Well, no version -- I'm trying to make Sylvain Le Gall's pr_gettext
work with camlp4 3.10.  It has to be linked into a standalone binary
called ocaml-xgettext, but I can't work out how to do that.

Previously Sylvain was using mkcamlp4, but that is broken.

Rich.

-- 
Richard Jones
Red Hat

Re: [Caml-list] camlp4 question: Mixing a printer and Ast.fold

[Nicolas Pouillard]

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Excerpts from Richard W.M. Jones's message of Fri Mar 21 17:56:25 +0100 2008:
> On Fri, Mar 21, 2008 at 05:50:00PM +0100, Nicolas Pouillard wrote:
> > Excerpts from Richard W.M. Jones's message of Fri Mar 21 17:44:30 +0100 2008:
> > > I'm trying to link the camlp4 module into a binary, by doing:
> > > 
> > >   ocamlc -I +camlp4 camlp4lib.cma Camlp4Bin.cmo pr_gettext.cmo \
> > >     -o ocaml-xgettext
> > > 
> > > but my binary always prints out:
> > > 
> > >   Failure: "No implementation printer"
> > > 
> > > Apparently I need to somehow register the printer as well?  I can't
> > > work out how to do that though.
> > 
> > What version of pr_gettext are you using?
> 
> Well, no version -- I'm trying to make Sylvain Le Gall's pr_gettext
> work with camlp4 3.10.  It has to be linked into a standalone binary
> called ocaml-xgettext, but I can't work out how to do that.
> 
> Previously Sylvain was using mkcamlp4, but that is broken.

I mean between different proposals for pr_gettext.ml, in this thread.

-- 
Nicolas Pouillard aka Ertai

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Re: [Caml-list] camlp4 question: Mixing a printer and Ast.fold

[Richard Jones]

On Fri, Mar 21, 2008 at 06:03:15PM +0100, Nicolas Pouillard wrote:
> Excerpts from Richard W.M. Jones's message of Fri Mar 21 17:56:25 +0100 2008:
> > On Fri, Mar 21, 2008 at 05:50:00PM +0100, Nicolas Pouillard wrote:
> > > Excerpts from Richard W.M. Jones's message of Fri Mar 21 17:44:30 +0100 2008:
> > > > I'm trying to link the camlp4 module into a binary, by doing:
> > > > 
> > > >   ocamlc -I +camlp4 camlp4lib.cma Camlp4Bin.cmo pr_gettext.cmo \
> > > >     -o ocaml-xgettext
> > > > 
> > > > but my binary always prints out:
> > > > 
> > > >   Failure: "No implementation printer"
> > > > 
> > > > Apparently I need to somehow register the printer as well?  I can't
> > > > work out how to do that though.
> > > 
> > > What version of pr_gettext are you using?
> > 
> > Well, no version -- I'm trying to make Sylvain Le Gall's pr_gettext
> > work with camlp4 3.10.  It has to be linked into a standalone binary
> > called ocaml-xgettext, but I can't work out how to do that.
> > 
> > Previously Sylvain was using mkcamlp4, but that is broken.
> 
> I mean between different proposals for pr_gettext.ml, in this thread.

I was using Jeremy Yallop's simple version (same as your first
version).  I got it to work by linking it as follows:

	$(OCAMLC)                                                            \
           -I +camlp4 camlp4lib.cma                                          \
           unix.cma                                                          \
          `$(OCAMLFIND) query -r -predicates byte gettext.extract -i-format` \
          `$(OCAMLFIND) query -r -predicates byte gettext.extract -a-format` \
          `$(OCAMLFIND) query -r -predicates byte gettext.extract -o-format` \
           Camlp4Bin.cmo                                                     \
          -o $@

Rich.

-- 
Richard Jones
Red Hat

Re: [Caml-list] camlp4 question: Mixing a printer and Ast.fold

[Richard Jones]

This is the patch to make ocaml-gettext work against ocaml 3.10.X:

http://www.annexia.org/tmp/ocaml-gettext-0.2.0-20080321.patch

Rich.

-- 
Richard Jones
Red Hat

Re: camlp4 question: Mixing a printer and Ast.fold

[Sylvain Le Gall]

On 21-03-2008, Richard Jones <rich@annexia.org> wrote:
>
> Thanks.  I've now got pr_gettext working again.
>
> BTW, I think the ability to be able to map & fold over the AST is an
> extraordinarily powerful feature, and deserves many more examples and
> tutorials.  I know that strictly speaking it was possible before (with
> Le Gall's ast-analyze extension) but the way it is done in the new
> camlp4 makes the code much shorter.
>

And it gives me one reason to drop ast-analyze... This new camlp4
feature, seems indeed very powerful.

Regards,
Sylvain Le Gall