Basic functionality is almost there, however still plenty to make it production quality. In this changeset I regenerated setup.ml via. oasis 3 so it contains a huge diff.

Ignore-this: 357d4c82baa1ecdf5c49bf65459059e9

darcs-hash:20120321031530-33bd9-43e454ae62709103edfb0208e7ab95a5319ae93a

_oasis

@@ -57,6 +57,15 @@ Library "utop-camlp4"
   XMETAType: syntax
   XMETADescription: Camlp4 integration
 
+Library "utop-camlp5"
+  FindlibName: camlp5
+  FindlibParent: utop
+  Path: src/camlp5
+  Modules: UTop_camlp5
+  BuildDepends: utop
+  XMETAType: syntax
+  XMETADescription: Camlp5 integration
+
 Executable utop
   Install: true
   Path: src/top

_tags

@@ -9,5 +9,8 @@
 # Use compiler interfaces
 <src/**/*.ml{,i}>: use_compiler_libs
 
+# Use camlp5
+<src/camlp5/**/*.ml{,i}>: use_camlp5
+
 # OASIS_START
 # OASIS_STOP

myocamlbuild.ml

@@ -47,6 +47,11 @@ let () =
              flag ["ocaml"; "ocamldep"; "use_compiler_libs"] & S paths;
              flag ["ocaml"; "doc"; "use_compiler_libs"] & S paths;
 
+             let paths = [A "-I"; A "+camlp5"] in
+             flag ["ocaml"; "compile"; "use_camlp5"] & S paths;
+             flag ["ocaml"; "ocamldep"; "use_camlp5"] & S paths;
+             flag ["ocaml"; "doc"; "use_camlp5"] & S paths;
+
              (* Expunge compiler modules *)
              rule "toplevel expunge"
                ~dep:"%.top"

src/camlp5/uTop_camlp5.ml

@@ -0,0 +1,66 @@
+(*
+ * uTop_camlp5.ml
+ * --------------
+ * Copyright : (c) 2012, Wojciech Meyer <wojciech.meyer@gmail.org>
+ * Licence   : BSD3
+ *
+ * This file is a part of utop.
+ *)
+
+open Lexing
+
+let print_camlp5_error pp exn =
+  let save = Format.get_formatter_output_functions () in
+  Format.set_formatter_output_functions 
+    (fun str s e -> Format.pp_print_string pp (String.sub str s e))
+    (fun () -> Format.pp_print_flush pp ());
+  Format.printf "@[<0>%a@]@." (fun _ -> Pcaml.report_error) exn;
+  Format.set_formatter_output_functions (fst save) (snd save)
+    
+let get_camlp5_error_message exn =
+  let loc, exn =
+    match exn with
+      | Ploc.Exc (loc, exn) ->
+          ((Ploc.first_pos loc, Ploc.last_pos loc), exn)
+      | exn ->
+          ((0, 0), exn)
+  in
+  let msg = UTop.get_message print_camlp5_error exn in
+  loc, msg
+
+let convert_camlp5_toplevel_phrase ast =
+  try
+    UTop.Value (Ast2pt.phrase ast)
+  with exn ->
+    let loc, msg = get_camlp5_error_message exn in
+    UTop.Error ([loc], msg)
+
+let parse_toplevel_phrase_camlp5 str eos_is_error =
+  try
+    let token_stream = Stream.of_string str in
+    match Grammar.Entry.parse Pcaml.top_phrase token_stream with
+      | Some ast ->
+          UTop.Value ast
+      | None ->
+          raise UTop.Need_more
+  with exn ->
+    if not eos_is_error then
+      raise UTop.Need_more
+    else
+      let loc, msg = get_camlp5_error_message exn in
+      UTop.Error ([loc], msg)
+
+let parse_toplevel_phrase str eos_is_error =
+  match parse_toplevel_phrase_camlp5 str eos_is_error with
+    | UTop.Value ast ->
+        convert_camlp5_toplevel_phrase ast
+    | UTop.Error (locs, msg) ->
+        UTop.Error (locs, msg)
+
+let () =
+  UTop.parse_toplevel_phrase := parse_toplevel_phrase;
+  (* Force camlp5 to display its welcome message. *)
+  try
+    ignore (!Toploop.parse_toplevel_phrase (Lexing.from_string ""))
+  with _ ->
+    ()

src/camlp5/uTop_camlp5.mli

@@ -0,0 +1,23 @@
+(*
+ * uTop_camlp5.mli
+ * ---------------
+ * Copyright : (c) 2012, Wojciech Meyer <wojciech.meyer@gmail.com>
+ * Licence   : BSD3
+ *
+ * This file is a part of utop.
+ *)
+
+val parse_toplevel_phrase : string -> bool -> Parsetree.toplevel_phrase UTop.result
+  (** Toplevel phrase parser for utop using camlp5. *)
+val parse_toplevel_phrase_camlp5 : string -> bool -> MLast.str_item UTop.result
+  (** Camlp5 toplevel phrase parser. Same as {!parse_toplevel_phrase}
+      but the result is not converted to an OCaml ast. *)
+
+val convert_camlp5_toplevel_phrase : MLast.str_item -> Parsetree.toplevel_phrase UTop.result
+  (** Converts a camlp5 toplevel phrase into a standard OCaml toplevel
+      phrase. Note that a camlp5 ast may not be convertible to an
+      OCaml one, in which case it returns {!UTop.Error}. *)
+
+val get_camlp5_error_message : exn -> UTop.location * string
+  (** [get_camlp5_error_message exn] returns the location and error
+      message for the exception [exn] as printed by camlp5. *)