[Caml-list] Some, None and the caml-C interface

[Caml-list] Some, None and the caml-C interface

[Yaron M. Minsky]

I've written some simple macros for accessing options in ocaml, and I
want to double check that they are actually right.  Does this look
right?  And is this documented anywhere?

#define Is_None(v)  (Is_long(v))
#define Is_Some(v)  (!Is_None(v))
#define Some_val(v) (Field(v,0))

Thanks,
Yaron

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Re: [Caml-list] Some, None and the caml-C interface

[Xavier Leroy]

> I've written some simple macros for accessing options in ocaml, and I
> want to double check that they are actually right.  Does this look
> right?

Yes, it is.

> And is this documented anywhere?

The general representation of sum datatypes is described in section
18.3.4 of the OCaml manual.  If you "instantiate" this description to
the actual definition of type option
        type 'a option = None | Some of 'a
you can derive the macros that you posted.

- Xavier Leroy
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