In a previous life I would write Camlp4 extension for fun, and I used the
syntax
  \( ... _ ...)
to abstract over an anonymous variables (you could also use \1 \2 \3 etc,
and the n-th occurence of _ from left to right was turned into \n, but
mixing numbers and _ was disallowed). It solves Scala's problem that, the
scope of _ being delimited by the closest parentheses, the notation was not
composable -- but arguably enforcing a small scope is a good thing.

This is the kind of features that nobody will ever agree on, so it's too
hard to get them in a language. Nowadays I write "(fun x ->" instead of
"\(", and "x" instead of "_", and it is not that bad.

Arthur Charguéraud has been working on an "easy-type-errors" mode with
better typing error messages for OCaml. You may be interested in his article
  http://www.chargueraud.org/research/2015/ocaml_errors/ocaml_errors.pdf
although I think this specific case of under-application is not discussed
(using too many argument is discussed).

I also find the work on SHErrLoc, by Danfeng Zhang, Andrew C. Myers and
their collaborators, to be very impressive:
  http://www.cs.cornell.edu/Projects/SHErrLoc/

On Sat, Nov 21, 2015 at 6:24 PM, Hendrik Boom <hendrik@topoi.pooq.com>
wrote:

> On Fri, Nov 06, 2015 at 01:34:11PM +0100, Gabriel Scherer wrote:
> >
> > I personally believe that currified constructor syntax would be a better
> > choice, and that using non-currified constructors is a historical mistake
> > of SML/Caml. But I am also not convinced that efforts to change it today
> > are worth the trouble, and prefer to concentrate on improving other parts
> > of the OCaml ecosystem.
>
> Perhaps there should be explicit syntax for currying, such as
>    f a b _
> instead of
>    f a b
> That would permit currying in other argument positions:
>    f a _ c
> though I suspect _ may be the wrong symbol for the current language, and
> I also suspect it's far too late tointroduce it in the current language.
>
> I have noticed that almost a the situations where the compiler thinks I
> mean to curry I actually just left out a parameter by mistake.  The type
> inferences it makes based on these errors usually occur elsewhere and
> are truly mystifying.
>
> -- hendrik
>
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