This is a bit of a pickle. For Real World OCaml to be a great book for
OCaml almost requires Core to become the stdlib. Core is a pretty nice body
of work, but I'm not a user of it myself, and I've been unable to decide if
I'd like it as the standard library. There is a very strong flavor to the
style. I suppose the official standard library has a bit of an
"exceptional" flavor, but aside from that I feel it doesn't impose anything.

Jean, for you example, the List.iter line using the standard library would
be:

    List.iter (fun x -> sum := !sum + x) list;

This kind of confusion is certainly not good for learning a language
though! To resolve this, we need to clone a single person three times and
send each into an alternate future: one continuing with standard library
as-is, one with Core, and one with Batteries. Then bring them back so they
can argue amongst each other about what was better. :)


On Sat, Nov 9, 2013 at 10:57 AM, Jean Saint-Remy <jeansaintremy@yahoo.com>wrote:

> Hi,
>
> I've been working out some of the examples in the
> https://realworldocaml.org/v1/en/html/a-guided-tour.html, which does
> utilize JaneStreet 'core' library. The new ocaml website is very
> impressive, as it allows you to dive right in into very fascinating
> idiomatic ocaml expressions. Just launching ocaml toplevel though is not
> enough.
>
> let sum list =
>   let sum  = ref 0 in
>   List.iter list ~f:(fun x -> sum := !sum + x);
>   !sum ;;
> -: Error: The function applied to this argument has type 'a list -> unit
>    This argument cannot be applied with label ~f
>
> Jean
>
>
>   On Saturday, November 9, 2013 5:07 AM, Gabriel Kerneis <
> gabriel@kerneis.info> wrote:
>  On Fri, Nov 08, 2013 at 07:33:35PM -0800, Jean Saint-Remy wrote:
> > I am running ocaml 3.12.1 and getting an error message. Is it an
> incompatible
> > version error or a missing 'core' module?
>
> Since you mention 'core', are you learning OCaml with "Real-World OCaml"
> (and
> hence trying to use JaneStreet's Core library instead of the standard one)?
> That would explain the discrepancy you are seeing.
>
>
> Best,
>
> --
> Gabriel
>
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>