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camlp4 module dependencies
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Date: 2008-09-21 (18:05)
From: Harrison, John R <john.r.harrison@i...>
Subject: camlp4 module dependencies
I'm trying once again to make some code work under the new camlp4. I
don't want to make any real syntax modifications, but just enable
quotations performing a simple string transformation on the body of
the quotation, e.g. turning

 <<hello /\ world>>


 default_parser "hello /\\ world"

About a year ago, Nicolas Pouillard gave me a recipe, which I've now
put in the following form for my actual requirements:

  open Camlp4.PreCast;;

  module Caml =

  let quotexpander s =
    if String.sub s 0 1 = "|" & String.sub s (String.length s - 1) 1 = "|" then
      "secondary_parser \""^
      (String.escaped (String.sub s 1 (String.length s - 2)))^"\""
    else "default_parser \""^(String.escaped s)^"\"";;

  let patt_quotexpander loc _loc_name_opt str =
    Gram.parse_string Caml.patt loc (quotexpander str);;

  let expr_quotexpander loc _loc_name_opt str =
    Gram.parse_string Caml.expr loc (quotexpander str);;

  let str_item_quotexpander loc loc_name_opt str =
    <:str_item@loc< $exp: expr_quotexpander loc loc_name_opt str$ >>;;

  let () =
    Syntax.Quotation.add "" Syntax.Quotation.DynAst.expr_tag expr_quotexpander;
    Syntax.Quotation.add "" Syntax.Quotation.DynAst.str_item_tag
    Syntax.Quotation.add "" Syntax.Quotation.DynAst.patt_tag patt_quotexpander;;

I can directly compile this file (say "Quotexpander.ml") with

  ocamlc -pp camlp4of -I +camlp4 -I +camlp4/Camlp4Parsers -a -o Quotexpander.cma Quotexpander.ml

and then use it inside the toplevel without problems:

  /home/johnh/temp/OCaml$ ocaml
          Objective Caml version 3.10.0

  # #load "camlp4o.cma";;
          Camlp4 Parsing version 3.10.0

  # #load "Quotexpander.cma";;
  # let default_parser s = s;;
  val default_parser : 'a -> 'a = <fun>
  # <<hello /\ world>>;;
  - : string = "hello /\\ world"

However, to keep the build process as trivial as possible, I'd like
simply to copy the ML code directly into the toplevel (i.e. #use
"Quotexpander.ml"). Doing this seems to hit some module dependencies,

  $ ocaml
          Objective Caml version 3.10.0

  #  #load "camlp4o.cma";;
          Camlp4 Parsing version 3.10.0

  #   open Camlp4.PreCast;;
  # module Caml =
  Unbound module Camlp4OCamlParser.Make

Can anyone tell me what else I should be loading/opening?