« Return to Thread: C++/OCaml bindings and the C++ std namespace

C++/OCaml bindings and the C++ std namespace

by Guillaume Yziquel-4 :: Rate this Message:

Hello.

I managed to bind an C++ library with Objective Caml. cf. below for the
toploop.

However, I needed to add a function converting a C char * to a C++
std::string:

> yziquel@seldon:~/svn/main/libmorfo-ocaml$ cat freeling.i
> %module freeling
> %{
>
> #include "freeling.h"
>
> std::string string_of_chars (char * c)
> {
> std:string s (c);
> return s;
> }
>
> %}
>
> class tokenizer {
> public:
> /// Constructor
> tokenizer(const std::string &);
>
> /// tokenize string with default options
> std::list<word> tokenize(const std::string &);
> /// tokenize string with default options, tracking offset in given int param.
> std::list<word> tokenize(const std::string &, unsigned long &);
> };
>
> std::string string_of_chars (char *);

There doesn't seem to be a standard way to convert an OCaml string to a
std::string. So I was wondering if there was a way to do something like

> class std::string {
> public
> string(char *)
> };

Moreover, it seems to me that the OCaml support in Swig isn't very well
suited for the needs of OCamlers. The Camlp4 syntax extension is
something that I really do not like, and the binded code is pretty much
typed in a way I dislike.

What documentation should I start reading to modify or rewrite the OCaml
plugin? Or, at least, to see what I could do?

All the best,

Guillaume Yziquel.

> yziquel@seldon:~/svn/main/libmorfo-ocaml$ ocaml freeling.cma
> Objective Caml version 3.11.0
>
> # module X = Freeling;;
> module X :
> sig
> type c_enum_type = [ `unknown ]
> type c_enum_value = [ `Int of int ]
> type c_obj = c_enum_value Swig.c_obj_t
> val module_name : string
> exception BadArgs of string
> exception BadMethodName of c_obj * string * string
> exception NotObject of c_obj
> exception NotEnumType of c_obj
> exception LabelNotFromThisEnum of c_obj
> exception InvalidDirectorCall of c_obj
> val new_tokenizer : c_obj -> c_obj
> val _new_tokenizer : c_obj -> c_obj
> val _delete_tokenizer : c_obj -> c_obj
> val create_tokenizer_from_ptr : c_obj -> c_obj
> val _string_of_chars : c_obj -> c_obj
> val enum_to_int : c_enum_type -> c_obj -> Swig.c_obj
> val int_to_enum : c_enum_type -> int -> c_obj
> val swig_val : c_enum_type -> c_obj -> Swig.c_obj
> end
> # open Freeling;;
> # let s = "/usr/share/freeling/en/tokenizer.dat";;
> val s : string = "/usr/share/freeling/en/tokenizer.dat"
> # let ss = C_string s;;
> Error: Unbound constructor C_string
> # open Swig;;
> # let ss = C_string s;;
> val ss : 'a Swig.c_obj_t = C_string "/usr/share/freeling/en/tokenizer.dat"
> # let sss = string_of_chars ss;;
> Error: Unbound value string_of_chars
> # let sss = _string_of_chars ss;;
> val sss : Freeling.c_obj = C_ptr (6710128L, 47161782545120L)
> # let tk = new_tokenizer sss;;
> val tk : Freeling.c_obj = C_obj <fun>

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« Return to Thread: C++/OCaml bindings and the C++ std namespace