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From: <john.else@citrix.com>
X-Mailer: Sympa 6.1.7
Date: Wed,  7 Nov 2012 16:54:58 +0100 (CET)
Subject: [Caml-list] C binding with labelled arguments

Hi,

If I have a C function like so:

CAMLprim value stub_add_ints(value first, value second) {
  CAMLparam2(first, second);
  int sum;

  sum = Int_val(first) + Int_val(second);
  CAMLreturn(Val_int(sum));
}

and I write an OCaml binding for it:

external add_ints : int -> int -> int  = "stub_add_ints"

is there any way to give the OCaml function labelled arguments, other than
writing a pure OCaml wrapper function? I'd like to be able to call

add_ints ~first:3 ~second:4;;

instead of just

add_ints 3 4;;

If I define the binding like this:

external add_ints : first:int -> second:int -> int  = "stub_add_ints"

it compiles, but the labels seem to be ignored - calling the function with
labelled arguments gives the error "This argument cannot be applied with label
~first", and looking up the function's type with OCamlSpotter indeed shows
that the function's type has no label information.

Thanks,
John