Re: [Caml-list] conjunctive type in polymorphic variants

["Conglun Yao" <yaoconglun@gmail.com>]

Nicolas and Olivier,

Thanks for your quick reply, it makes sense!

Conglun

On Thu, Oct 9, 2008 at 9:43 AM, Olivier Andrieu <oandrieu@nerim.net> wrote:
> Hi,
>
> On Thu, Oct 9, 2008 at 06:15, Conglun Yao <yaoconglun@gmail.com> wrote:
>> Sorry, I can't fully understand the source code, but it seems we can
>> only define a polymorphic variant with only one additional type
>> declaration, like
>>               `A of int   or `A of (int * int)
>>  rather than `A of int * int
>
> That's correct.
>
>> It looks wired, as we can directly define
>> type t = [ `A of int * int | `B of string ]  in toploop or a *.ml file.
>
> yes, that's because ocaml handle the "of int * int" a bit differently
> in regular and
> polymorphic variant declarations:
>  - in the regular variant the * is a separator between constructor
> arguments (thus two arguments)
>  - polymorphic variants only have one argument, so int * int is
> treated as a whole type expression and * is the "tupling" operator
>
> So yes, this looks wired in the ocaml parser.
>
> --
>  Olivier
>