Re: [Caml-list] C binding with labelled arguments

[Gabriel Scherer <gabriel.scherer@gmail.com>]

Given that the argument passing order of labelled functions is not
specified, it seems like it would be really safer to use a wrapper
function. Why wouldn't you do this?
(If that is for performance reason, the wrapper should be inlined when
used from inside the same module, and if you want to expose the
external globally you can always re-define it along with its wrapper
in any module.)

On Wed, Nov 7, 2012 at 4:54 PM,  <john.else@citrix.com> wrote:
> 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
>
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